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When measles broke out in 31 states several years ago, health experts were surprised to see more than 1,200 confirmed cases –– the largest number reported in the US since 1992.

Measles is a very contagious, preventable illness that may cause serious health complications, especially in younger children and people who are pregnant, or whose immune systems aren’t working well. While a highly effective vaccine is available, vaccination rates are low in some communities across the US. This sets the stage for large outbreaks.

Here are four things that everyone needs to know about measles.

Measles is highly contagious

This is a point that can’t be stressed enough. A full 90% of unvaccinated people exposed to the virus will catch it. And if you think that just staying away from sick people will do the trick, think again. Not only are people with measles infectious for four days before they break out with the rash, but the virus can live in the air for up to two hours after an infectious person coughs or sneezes. Just imagine: if an infectious person sneezes in an elevator, everyone riding that elevator for the next two hours could be exposed.

It’s hard to know that a person has measles when they first get sick

The first symptoms of measles are a high fever, cough, runny nose, and red, watery eyes (conjunctivitis), which could be confused with any number of other viruses, especially during cold and flu season. After two or three days people develop spots in the mouth called Koplik spots, but we don’t always go looking in our family members’ mouths. The characteristic rash develops three to five days after the symptoms begin, as flat red spots that start on the face at the hairline and spread downward all over the body. At that point you might realize that it isn’t a garden-variety virus — and at that point, the person would have been spreading germs for four days.

Measles can be dangerous

Most of the time, as with other childhood viruses, people weather it fine, but there can be complications. Children less than 5 years old and adults older than 20 are at highest risk of complications. Common and milder complications include diarrhea and ear infections (although the ear infections can lead to hearing loss), and one out of five will need to be hospitalized, but there also can be serious complications:

• One in 20 people with measles gets pneumonia. This is the most common cause of death from the illness.
• One in 1,000 gets encephalitis, an inflammation of the brain that can lead to seizures, deafness, or even brain damage.
• One to three in 1,000 children who get it will die.

Another possible complication can occur seven to 10 years after infection, more commonly when people get the infection as infants. It’s called subacute sclerosing panencephalitis, or SSPE. While it is rare (four to 11 out of 100,000 infections), it is fatal.

Vaccination prevents measles

The measles vaccine, usually given as part of the MMR (measles-mumps-rubella) vaccine, can make all the difference. One dose is 93% effective in preventing illness; two doses gets that number up to 97%. 

• Usually, the first dose is given between ages 12 to 15 months.
• A second (booster) dose is commonly given between ages 4 to 6, although it can be given as early as a month after the first dose.
• If an infant ages 6 to 12 months will be going to a place where measles regularly occurs, a dose of vaccine can be given as protection. This extra dose will not count as part of the required series of two vaccines.

The MMR is overall a very safe vaccine. Most side effects are mild, and it does not cause autism. Most children in the US are vaccinated, with 91% of 24-month-olds having at least one dose and about 93% of those entering kindergarten having two doses.

Herd immunity occurs when enough people are vaccinated that it’s hard for the illness to spread. It helps protect those who can’t get the vaccine, such as young infants or those with weak immune systems. To achieve this you need about 95% vaccination, so the 93% isn’t perfect — and in some states and communities, that number is even lower. Most of the outbreaks we have seen over the years have started in areas where there are high numbers of unvaccinated children.

If you have questions about measles or the measles vaccine, talk to your doctor. The most important thing is that we keep every child, every family, and every community safe.

About the Author

Claire McCarthy, MD, Senior Faculty Editor, Harvard Health Publishing

Claire McCarthy, MD, is a primary care pediatrician at Boston Children’s Hospital, and an assistant professor of pediatrics at Harvard Medical School. In addition to being a senior faculty editor for Harvard Health Publishing, Dr. McCarthy … See Full Bio View all posts by Claire McCarthy, MD

Maybe we should add toothbrushes to the bouquet of flowers we bring to friends and family members in the hospital — and make sure to pack one if we wind up there ourselves.

New Harvard-led research published online in JAMA Internal Medicine suggests seriously ill hospitalized patients are far less likely to develop hospital-acquired pneumonia if their teeth are brushed twice daily. They also need ventilators for less time, are able to leave the intensive care unit (ICU) more quickly, and are less likely to die in the ICU than patients without a similar toothbrushing regimen.

Why would toothbrushing make any difference?

“It makes sense that toothbrushing removes the bacteria that can lead to so many bad outcomes,” says Dr. Tien Jiang, an instructor in oral health policy and epidemiology at Harvard School of Dental Medicine, who wasn’t involved in the new research. “Plaque on teeth is so sticky that rinsing alone can’t effectively dislodge the bacteria. Only toothbrushing can.”

Pneumonia consistently falls among the leading infections patients develop while hospitalized. According to the Agency for Healthcare Research and Quality, each year more than 633,000 Americans who go to the hospital for other health issues wind up getting pneumonia. Air sacs (alveoli) in one or both lungs fill with fluid or pus, causing coughing, fever, chills, and trouble breathing. Nearly 8% of those who develop hospital-acquired pneumonia die from it.

How was the study done?

The researchers reviewed 15 randomized trials encompassing nearly 2,800 patients. All of the studies compared outcomes among seriously ill hospitalized patients who had daily toothbrushing to those who did not.

• 14 of the studies were conducted in ICUs
• 13 involved patients who needed to be on a ventilator
• 11 used an antiseptic rinse called chlorhexidine gluconate for all patients: those who underwent toothbrushing and those who didn’t.

What were the findings?

The findings were compelling and should spur efforts to standardize twice-daily toothbrushing for all hospitalized patients, Dr. Jiang says.

Study participants who were randomly assigned to receive twice-daily toothbrushing were 33% less likely to develop hospital-acquired pneumonia. Those effects were magnified for people on ventilators, who needed this invasive breathing assistance for less time if their teeth were brushed.

Overall, study participants were 19% less likely to die in the ICU — and able to graduate from intensive care faster — with the twice-daily oral regimen.

How long patients stayed in the hospital or whether they were treated with antibiotics while there didn’t seem to influence pneumonia rates. Also, toothbrushing three or more times daily didn’t translate into additional benefits over brushing twice a day.

What were the study’s strengths and limitations?

One major strength was compiling years of smaller studies into one larger analysis — something particularly unusual in dentistry, Dr. Jiang says. “From a dental point of view, having 15 randomized controlled trials is huge. It’s very hard to amass that big of a population in dentistry at this high a level of evidence,” she says.

But toothbrushing techniques may have varied among hospitals participating in the research. And while the study was randomized, it couldn’t be blinded — a tactic that would reduce the chance of skewed results. Because there was no way to conceal toothbrushing regimens, clinicians involved in the study likely knew their efforts were being tracked, which may have changed their behavior.

“Perhaps they were more vigilant because of it,” Dr. Jiang says.

How exactly can toothbrushing prevent hospital-acquired pneumonia?

It’s not complicated. Pneumonia in hospitalized patients often stems from breathing germs into the mouth — germs which number more than 700 different species, including bacteria, fungi, viruses and other microbes.

This prospect looms larger for ventilated patients, since the breathing tube inserted into the throat can carry bacteria farther down the airway. “Ventilated patients lose the normal way of removing some of this bacteria,” Dr. Jiang says. “Without that ventilator, we can sweep it out of our upper airways.”

How much does toothbrushing matter if you’re not hospitalized?

In case you think the study findings only pertain to people in the hospital, think again. Rather, this drives home how vital it is for everyone to take care of their teeth and gums.

About 300 diseases and conditions are linked in some way to oral health. Poor oral health triggers some health problems and worsens others. People with gum disease and tooth loss, for example, have higher rates of heart attacks. And those with uncontrolled gum disease typically have more difficulty controlling blood sugar levels.

About the Author

Maureen Salamon, Executive Editor, Harvard Women's Health Watch

Maureen Salamon is executive editor of Harvard Women’s Health Watch. She began her career as a newspaper reporter and later covered health and medicine for a wide variety of websites, magazines, and hospitals. Her work has … See Full Bio View all posts by Maureen Salamon

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

When you first learned the facts about pregnancy — from a parent, perhaps, or a friend — you probably didn’t learn that up to one in three ends in a miscarriage.

What causes miscarriage? How is it treated? And why is appropriate health care for miscarriage under scrutiny — and in some parts of the US, getting harder to find?

What is miscarriage?

Many people who come to us for care are excited and hopeful about building their families. It’s devastating when a hoped-for pregnancy ends early.

Miscarriage is a catch-all term for a pregnancy loss before 20 weeks, counting from the first day of the last menstrual period. Miscarriage happens in as many as one in three pregnancies, although the risk gradually decreases as pregnancy progresses. By 20 weeks, it occurs in fewer than one in 100 pregnancies.

What causes miscarriage?

Usually, there is no obvious or single cause for miscarriage. Some factors raise risk, such as:

• Pregnancy at older ages. Chromosome abnormalities are a common cause of pregnancy loss. As people age, this risk rises.
• Autoimmune disorders. While many pregnant people with autoimmune disorders like lupus or Sjogren’s syndrome have successful pregnancies, their risk for pregnancy loss is higher.
• Certain illnesses. Diabetes or thyroid disease, if poorly controlled, can raise risk.
• Certain conditions in the uterus. Uterine fibroids, polyps, or malformations may contribute to miscarriage.
• Previous miscarriages. Having a miscarriage slightly increases risk for miscarriage in the next pregnancy. For instance, if a pregnant person’s risk of miscarriage is one in 10, it may increase to 1.5 in 10 after their first miscarriage, and four in 10 after having three miscarriages.
• Certain medicines. A developing pregnancy may be harmed by certain medicines. It’s safest to plan pregnancy and receive pre-pregnancy counseling if you have a chronic illness or condition.

How is miscarriage diagnosed?

Before ultrasounds in early pregnancy became widely available, many miscarriages were diagnosed based on symptoms like bleeding and cramping. Now, people may be diagnosed with a miscarriage or early pregnancy loss on a routine ultrasound before they notice any symptoms.

How is miscarriage treated?

Being able to choose the next step in treatment may help emotionally. When there are no complications and the miscarriage occurs during the first trimester (up to 13 weeks of pregnancy), the options are:

Take no action. Passing blood and pregnancy tissue often occurs at home naturally, without need for medications or a procedure. Within a week, 25% to 50% will pass pregnancy tissue; more than 80% of those who experience bleeding as a sign of miscarriage will pass the pregnancy tissue within two weeks.

What to know: This can be a safe option for some people, but not all. For example, heavy bleeding would not be safe for a person who has anemia (lower than normal red blood cell counts).

Take medication. The most effective option uses two medicines: mifepristone is taken first, followed by misoprostol. Using only misoprostol is a less effective option. The two-step combination is 90% successful in helping the body pass pregnancy tissue; taking misoprostol alone is 70% to 80% successful in doing so.

What to know: Bleeding and cramping typically start a few hours after taking misoprostol. If bleeding does not start, or there is pregnancy tissue still left in the uterus, a surgical procedure may be necessary: this happens in about one in 10 people using both medicines and one in four people who use only misoprostol.

Use a procedure. During dilation and curettage (D&C), the cervix is dilated (widened) so that instruments can be inserted into the uterus to remove the pregnancy tissue. This procedure is nearly 99% successful.

What to know: If someone is having life-threatening bleeding or has signs of infection, this is the safest option. This procedure is typically done in an operating room or surgery center. In some instances, it is offered in a doctor’s office.

If you have a miscarriage during the second trimester of pregnancy (after 13 weeks), discuss the safest and best plan with your doctor. Generally, second trimester miscarriages will require a procedure and cannot be managed at home.

Red flags: When to ask for help during a miscarriage

During the first 13 weeks of pregnancy: Contact your health care provider or go to the emergency department immediately if you experience

• heavy bleeding combined with dizziness, lightheadedness, or feeling faint
• fever above 100.4° F
• severe abdominal pain not relieved by over-the-counter pain medicine, such as acetaminophen (Tylenol) or ibuprofen (Motrin, Advil). Please note: ibuprofen is not recommended during pregnancy, but is safe to take if a miscarriage has been diagnosed.

After 13 weeks of pregnancy: Contact your health care provider or go to the emergency department immediately if you experience

• any symptoms listed above
• leakage of fluid (possibly your water may have broken)
• severe abdominal or back pain (similar to contractions).

How is care for miscarriages changing?

Unfortunately, political interference has had significant impact on safe, effective miscarriage care:

• Some states have banned a procedure used to treat second trimester miscarriage. Called dilation and evacuation (D&E), this removes pregnancy tissue through the cervix without making any incisions. A D&E can be lifesaving in instances when heavy bleeding or infection is complicating a miscarriage.
• Federal and state lawsuits, or laws banning or seeking to ban mifepristone for abortion care, directly limit access to a safe, effective drug approved for miscarriage care. This could affect miscarriage care nationwide.
• Many laws and lawsuits that interfere with miscarriage care offer an exception to save the life of a pregnant patient. However, miscarriage complications may develop unexpectedly and worsen quickly, making it hard to ensure that people will receive prompt care in life-threatening situations.
• States that ban or restrict abortion are less likely to have doctors trained to perform a full range of miscarriage care procedures. What’s more, clinicians in training, such as resident physicians and medical students, may never learn how to perform a potentially lifesaving procedure.

Ultimately, legislation or court rulings that ban or restrict abortion care will decrease the ability of doctors and nurses to provide the highest quality miscarriage care. We can help by asking our lawmakers not to pass laws that prevent people from being able to get reproductive health care, such as restricting medications and procedures for abortion and miscarriage care.

About the Authors

Sara Neill, MD, MPH, Contributor

Dr. Sara Neill is a physician-researcher in the department of obstetrics & gynecology at Beth Israel Deaconess Medical Center and Harvard Medical School. She completed a fellowship in complex family planning at Brigham and Women's Hospital, and … See Full Bio View all posts by Sara Neill, MD, MPH

Scott Shainker, DO, MS, Contributor

Scott Shainker, D.O, M.S., is a maternal-fetal medicine specialist in the Department of Obstetrics and Gynecology at Beth Israel Deaconess Medical Center (BIDMC). He is also a member of the faculty in the Department of Obstetrics, … See Full Bio View all posts by Scott Shainker, DO, MS

Don’t worry. It’s good advice if you can take it. Of course that’s not always easy, especially for health concerns.

The truth is: it’s impossible (and ill-advised) to never worry about your health. But are you worrying about the right things? Let’s compare a sampling of common worries to the most common conditions that actually shorten lives. Then we can think about preventing the biggest health threats.

Dangerous but rare health threats

The comedian John Mulaney says the cartoons he watched as a child gave him the impression that quicksand, anvils falling from the sky, and lit sticks of dynamite represented major health risks. For him (as is true for most of us), none of these turned out to be worth worrying about.

While harm can befall us in many ways, some of our worries are not very likely to occur:

• Harm by lightning: In the US, lightning strikes kill about 25 people each year. Annually, the risk for the average person less than one in a million. There are also several hundred injuries due to nonfatal lightning strikes. Even though lightning strikes the earth millions of times each year, the chances you’ll be struck are quite low.
• Dying in a plane crash: The yearly risk of being killed in a plane crash for the average American is about one in 11 million. Of course, the risk is even lower if you never fly, and higher if you regularly fly on small planes in bad weather with inexperienced pilots. By comparison, the average yearly risk of dying in a car accident is approximately 1 in 5,000.
• Snakebite injuries and deaths: According to the Centers for Disease Control and Prevention, an estimated 7,000 to 8,000 people are bit by poisonous snakes each year in the US. Lasting injuries are uncommon, and deaths are quite rare (about five per year). In parts of the country where no poisonous snakes live, the risk is essentially zero.
• Shark attacks: As long as people aren’t initiating contact with sharks, attacks are fairly uncommon. Worldwide, about 70 unprovoked shark attacks occur in an average year, six of which are fatal. In 2022, 41 attacks occurred in the US, two of which were fatal.
• Public toilet seats: They may appear unclean (or even filthy), but they pose little or no health risk to the average person. While it’s reasonable to clean off the seat and line it with paper before touching down, health fears should not discourage you from using a public toilet.

I’m not suggesting that these pose no danger, especially if you’re in situations of increased risk. If you’re on a beach where sharks have been sighted and seals are nearby, it’s best not to swim there. When in doubt, it’s a good idea to apply common sense and err on the side of safety.

What do Google and TikTok tell us about health concerns?

Analyzing online search topics can tell us a lot about our health worries.

The top Google health searches in 2023 were:

• How long is strep throat contagious?
• How contagious is strep throat?
• How to lower cholesterol?
• What helps with bloating?
• What causes low blood pressure?

Really? Cancer, heart disease and stroke, or COVID didn’t reach the top five? High blood pressure didn’t make the list, but low blood pressure did?

Meanwhile, on TikTok the most common topics searched were exercise, diet, and sexual health, according to one study. Again, no top-of-the-list searches on the most common and deadly diseases.

How do our worries compare with the top causes of death?

In the US, these five conditions took the greatest number of lives in 2022:

• heart disease
• cancer
• unintentional injury (including motor vehicle accidents, drug overdoses, and falls)
• COVID-19
• stroke.

This list varies by age. For example, guns are the leading cause of death among children and teenagers (ages 1 to 19). For older teens (ages 15 to 19), the top three causes of death were accidents, homicide, and suicide.

Perhaps the lack of overlap between leading causes of death and most common online health-related searches isn’t surprising. Younger folks drive more searches and may not have heart disease, cancer, or stroke at top of mind. In addition, online searches might reflect day-to-day concerns (how soon can my child return to school after having strep throat?) rather than long-term conditions, such as heart disease or cancer. And death may not be the most immediate health outcome of interest.

But the disconnect suggests to me that we may be worrying about the wrong things — and focusing too little on the biggest health threats.

Transforming worry into action

Most of us can safely worry less about catching something from a toilet seat or shark attacks. Instead, take steps to reduce the risks you face from our biggest health threats. Chipping away at these five goals could help you live longer and better while easing unnecessary worry:

• Choose a heart-healthy diet.
• Get routinely recommended health care, including blood pressure checks and cancer screens, such as screening for colorectal cancer.
• Drive more safely. Obey the speed limit, drive defensively, always wear a seatbelt, and don’t drive if you’ve been drinking.
• Don’t smoke. If you need to quit, find help.
• Get regular exercise.

The bottom line

Try not to focus too much on health risks that are unlikely to affect you. Instead, think about common causes of poor health. Then take measures to reduce your risk. Moving more and adding healthy foods to your meals is a great start.

And in case you’re curious, the average number of annual deaths due to quicksand is zero in the US. Still a bit worried? Fine, here’s a video that shows you how to save yourself from quicksand even though you’ll almost certainly never need it.

About the Author

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD

All of us have an internal clock that regulates our circadian rhythms, including when we sleep and when we are awake. And light is the single most important factor that helps establish when we should feel wakeful (generally during the day) and when we should feel sleepy (typically at night).

So, let me ask you a personal question: just how dark is your bedroom? To find out why that matters — and whether sleeping in an eye mask is worthwhile — read on.

How is light related to sleep?

Our circadian system evolved well before the advent of artificial light. As anyone who has been to Times Square can confirm, just a few watts of power can trick the brain into believing that it is daytime at any time of night. So, what’s keeping your bedroom alight?

• A tablet used in bed at night to watch a movie is more than 100 times brighter than being outside when there is a full moon.
• Working on or watching a computer screen at night is about 10 times brighter than standing in a well-lit parking lot.

Light exposure at night affects the natural processes that help prepare the body for sleep. Specifically, your pineal gland produces melatonin in response to darkness. This hormone is integral for the circadian regulation of sleep.

What happens when we are exposed to light at night?

Being exposed to light at night suppresses melatonin production, changing our sleep patterns. Compared to sleeping without a night light, adults who slept next to a night light had shallower sleep and more frequent arousals. Even outdoor artificial light at night, such as street lamps, has been linked with getting less sleep.

But the impact of light at night is not limited to just sleep. It’s also associated with increased risk of developing depressive symptoms, obesity, diabetes, and high blood pressure. Light exposure misaligned with our circadian rhythms — that is, dark during the day and light at night — is one reason scientists believe that shift work puts people at higher risk for serious health problems.

Could sleeping with an eye mask help?

Researchers from Cardiff University in the United Kingdom conducted a series of experiments to see if wearing an eye mask while sleeping at night could improve certain measures of learning and alertness.

Roughly 90 healthy young adults, 18 to 35 years of age, alternated between sleeping while wearing an eye mask or being exposed to light at night. They recorded their sleep patterns in a sleep diary.

In the first part of the study, participants wore an intact eye mask for a week. Then during the next week, they wore an eye mask with a hole exposing each eye so that the mask didn't block the light.

After sleeping with no light exposure (wearing the intact eye mask) and with minimal light exposure (the eye mask with the holes), participants completed three cognitive tasks on days six and seven of each week:

• First was a paired-associate learning task. This helps show how effectively a person can learn new associations. Here the task was learning related word pairs. Participants performed better after wearing an intact eye mask during sleep in the days leading up to the test than after being exposed to light at night.
• Second, the researchers administered a psychomotor vigilance test, which assesses alertness. Blocking light at night also improved reaction times on this task.
• Finally, a motor skill learning test was given, which involved tapping a five-digit sequence in the correct order. For this task, there was no difference in performance whether participants had worn an intact eye mask or been exposed to light at night.

What else did the researchers learn?

No research study is ever perfect, so it is important to take the conclusions above with a grain of salt.

According to sleep diary data, there was no difference in the amount of sleep, nor in their perceptions of sleep quality, regardless of whether people wore an eye mask or not.

Further, in a second experiment with about 30 participants, the researchers tracked sleep objectively using a monitoring device called the Dreem headband. They found no changes to the structure of sleep — for example, how much time participants spent in REM sleep — when wearing an eye mask.

Should I rush out to buy an eye mask before an important meeting or exam?

If you decide to try using an eye mask, you probably don’t need to pay extra for overnight shipping. Instead, follow a chronobiologist’s rule of thumb: “bright days, dark nights.”

• During the daytime, get as much natural daylight as you possibly can: go out to pick up your morning bagel from a local bakery, take a short walk during your afternoon lull at work.
• In the evening, reduce your exposure to electronic devices such as your cell phone, and use the night-dimming modes on these devices. Make sure that you turn off all unnecessary lights. Finally, try to make your bedroom as dark as possible when you go to bed. This could mean turning the alarm clock next to your bed away from you or covering up the light on a humidifier.

Of course, you might decide a well-fitted, comfortable eye mask is a useful addition to your light hygiene toolkit. Most cost $10 to $20, so you may find yourself snoozing better and improving cognitive performance for the price of a few cups of coffee.

About the Author

Eric Zhou, PhD, Contributor

Eric Zhou, PhD, is an assistant professor at Harvard Medical School. His research focuses on how we can better understand and treat sleep disorders in both pediatric and adult populations, including those with chronic illnesses. Dr. … See Full Bio View all posts by Eric Zhou, PhD

Chronic fatigue syndrome (CFS) –– or myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), to be specific ––  is an illness defined by a group of symptoms. Yet medical science always seeks objective measures that go beyond the symptoms people report.

A new study from the National Institutes of Health (NIH) has performed more diverse and extensive biological measurements of people experiencing CFS than any previous research. Using immune testing, brain scans, and other tools, the researchers looked for abnormalities that might drive health complaints like crushing fatigue and brain fog. Let’s dig into what they found and what it means.

What was already known about chronic fatigue syndrome?

In people with chronic fatigue syndrome, there are underlying abnormalities in many parts of the body: The brain. The immune system. The way the body generates energy. Blood vessels. Even in the microbiome, the bacteria that live in the gut. These abnormalities have been reported in thousands of published studies over the past 40 years.

Who participated in the NIH study?

Published in February in Nature Communications, this small NIH study compared people who developed chronic fatigue syndrome after having some kind of infection with a healthy control group.

Those with CFS had been perfectly healthy before coming down with what seemed like just a simple “flu”: sore throat, coughing, aching muscles, and poor energy. However, unlike their experiences with past flulike illnesses, they did not recover. For years, they were left with debilitating fatigue, difficulty thinking, a flare-up of symptoms after exerting themselves physically or mentally, and other symptoms. Some were so debilitated that they were bedridden or homebound.

All the participants spent a week at the NIH, located outside of Washington, DC. Each day they received different tests. The extensive testing is the great strength of this latest study.

What are three important findings from the study?

The study had three key findings, including one important new discovery.

First, as was true in many previous studies, the NIH team found evidence of chronic activation of the immune system. It seemed as if the immune system was engaged in a long war against a foreign microbe — a war it could not completely win and therefore had to keep fighting.

Second, the study found that a part of the brain known to be important in perceiving fatigue and encouraging effort — the right temporal-parietal area — was not functioning normally. Normally, when healthy people are asked to exert themselves physically or mentally, that area of the brain lights up during an MRI. However, in the people with CFS it lit up only dimly when they were asked to exert themselves.

While earlier research had identified many other brain abnormalities, this one was new. And this particular change makes it more difficult for people with CFS to exert themselves physically or mentally, the team concluded. It makes any effort like trying to swim against a current.

Third, in the spinal fluid, levels of various brain chemicals called neurotransmitters and markers of inflammation differed in people with CFS compared with the healthy comparison group. The spinal fluid surrounds the brain and reflects the chemistry of the brain.

What else did study show?

There are some other interesting findings in this study. The team found significant differences in many biological measurements between men and women with chronic fatigue syndrome. This surely will lead to larger studies to verify these gender-based differences, and to determine what causes them.

There was no difference between people with CFS and the healthy comparison group in the frequency of psychiatric disorders — currently, or in the past. That is, the symptoms of the illness could not be attributed to psychological causes.

Is chronic fatigue syndrome all in the brain?

The NIH team concluded that chronic fatigue syndrome is primarily a disorder of the brain, perhaps brought on by chronic immune activation and changes in the gut microbiome. This is consistent with the results of many previous studies.

The growing recognition of abnormalities involving the brain, chronic activation (and exhaustion) of the immune system, and of alterations in the gut microbiome are transforming our conception of CFS –– at least when caused by a virus. And this could help inform potential treatments.

For example, the NIH team found that some immune system cells are exhausted by their chronic state of activation. Exhausted cells don’t do as good a job at eliminating infections. The NIH team suggests that a class of drugs called immune checkpoint inhibitors may help strengthen the exhausted cells.

What are the limitations of the study?

The number of people who were studied was small: 17 people with ME/CFS and 21 healthy people of the same age and sex, who served as a comparison group. Unfortunately, the study had to be stopped before it had enrolled more people, due to the COVID-19 pandemic.

That means that the study did not have a great deal of statistical power and could have failed to detect some abnormalities. That is the weakness of the study.

The bottom line

This latest study from the NIH joins thousands of previously published scientific studies over the past 40 years. Like previous research, it also finds that people with ME/CFS have measurable abnormalities of the brain, the immune system, energy metabolism, the blood vessels, and bacteria that live in the gut.

What causes all of these different abnormalities? Do they reinforce each other, producing spiraling cycles that lead to chronic illness? How do they lead to the debilitating symptoms of the illness? We don’t yet know. What we do know is that people are suffering and that this illness is afflicting millions of Americans. The only sure way to a cure is studies like this one that identify what is going wrong in the body. Targeting those changes can point the way to effective treatments.

About the Author

Anthony L. Komaroff, MD, Editor in Chief, Harvard Health Letter

Dr. Anthony L. Komaroff is the Steven P. Simcox/Patrick A. Clifford/James H. Higby Professor of Medicine at Harvard Medical School, senior physician at Brigham and Women’s Hospital in Boston, and editor in chief of the Harvard … See Full Bio View all posts by Anthony L. Komaroff, MD

Snuff is a smokeless tobacco similar to chewing tobacco. It rarely makes headlines. But it certainly did when the FDA authorized a brand of snuff to market its products as having a major health advantage over cigarettes. Could this be true? Is it safe to use snuff?

What did the FDA authorize as a health claim?

Here’s the approved language for Copenhagen Classic Snuff:

If you smoke, consider this: switching completely to this product from cigarettes reduces risk of lung cancer.

While the statement is true, this FDA action — and the marketing that’s likely to follow — might suggest snuff is a safe product. It’s not. Let’s talk about the rest of the story.

What is snuff, anyway?

Snuff is a form of tobacco that’s finely ground. There are two types:

• Moist snuff. Users place a pinch or a pouch of tobacco behind their upper or lower lips or between their cheek and gum. They must repeatedly spit out or swallow the tobacco juice that accumulates. After a few minutes, they remove or spit out the tobacco as well. This recent FDA action applies to a brand of moist snuff.
• Dry snuff. This type is snorted (inhaled through the nose) and is less common in the US.

Both types are available in an array of scents and flavors. Users absorb nicotine and other chemicals into the bloodstream through the lining of the mouth. Blood levels of nicotine are similar between smokers and snuff users. But nicotine stays in the blood for a longer time with snuff users.

Why is snuff popular?

According to CDC statistics, 5.7 million adults in the US regularly use smokeless tobacco products — that’s about 2% of the adult population. A similar percentage (1.6%) of high school students use it as well. That’s despite restrictions on youth marketing and sales.

What accounts for its popularity?

• Snuff may be allowed in places that prohibit smoking.
• It tends to cost less than cigarettes: $300 to $1,000 a year versus several thousand dollars a year paid by some smokers.
• It doesn’t require inhaling smoke into the lungs, or exposing others to secondhand smoke.
• Snuff is safer than cigarettes in at least one way — it is less likely to cause lung cancer.
• It may help some cigarette smokers quit.

The serious health risks of snuff

While the risk of lung cancer is lower compared with cigarettes, snuff has plenty of other health risks, including

• higher risk of cancers of the mouth (such as the tongue, gums, and cheek), esophagus, and pancreas
• higher risk of heart disease and stroke
• harm to the developing teenage brain
• dental problems, such as discoloration of teeth, gum disease, tooth damage, bone loss around the teeth, tooth loosening or loss
• higher risk of premature birth and stillbirth among pregnant users.

And because nicotine is addictive, using any tobacco product can quickly become a habit that’s hard to break.

There are also the “ick” factors: bad breath and having to repeatedly spit out tobacco juice.

Could this new marketing message about snuff save lives?

Perhaps, if many smokers switch to snuff and give up smoking. That could reduce the number of people who develop smoking-related lung cancer. It might even reduce harms related to secondhand smoke.

But it’s also possible the new marketing message will attract nonsmokers, including teens, who weren’t previously using snuff. A bigger market for snuff products might boost health risks for many people, rather than lowering them.

The new FDA action is approved for a five-year period, and the company must monitor its impact. Is snuff an effective way to help smokers quit? Is a lower rate of lung cancer canceled out by a rise in other health risks? We don’t know yet. If the new evidence shows more overall health risks than benefits for snuff users compared with smokers, this new marketing authorization may be reversed.

The bottom line

If you smoke, concerns you have about lung cancer or other smoking-related health problems are justified. But snuff should not be the first choice to help break the smoking habit. Commit to quit using safer options that don’t involve tobacco, such as nicotine gum or patches, counseling, and medications.

While the FDA’s decision generated news headlines that framed snuff as safer than smoking, it’s important to note that the FDA did not endorse the use of snuff — or even suggest that snuff is a safe product. Whether smoked or smokeless, tobacco creates enormous health burdens and suffering. Clearly, it’s best not to use any tobacco product.

Until we have a better understanding of its impact, I think any new marketing of this sort should also make clear that using snuff comes with other important health risks — even if lung cancer isn’t the biggest one.

Follow me on Twitter @RobShmerling

About the Author

Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School. … See Full Bio View all posts by Robert H. Shmerling, MD

If you've been cocooning due to winter’s cold, who can blame you? But a lack of activity isn't good for body or mind during any season. And whether you're deep in the grip of winter or fortunate to be basking in signs of spring, today is a good day to start exercising. If you’re not sure where to start — or why you should — we’ve shared tips and answers below.

Moving more: What’s in it for all of us?

We’re all supposed to strengthen our muscles at least twice a week and get a total at least 150 minutes of weekly aerobic activity (the kind that gets your heart and lungs working). But fewer than 18% of U.S. adults meet those weekly recommendations, according to the CDC.

How can choosing to become more active help? A brighter mood is one benefit: physical activity helps ease depression and anxiety, for example. And being sufficiently active — whether in short or longer chunks of time — also lowers your risk for health problems like

• heart disease
• stroke
• diabetes
• cancer
• brain shrinkage
• muscle loss
• weight gain
• poor posture
• poor balance
• back pain
• and even premature death.

What are your exercise obstacles?

Even when we understand these benefits, a range of obstacles may keep us on the couch.

Don’t like the cold? Have trouble standing, walking, or moving around easily? Just don’t like exercise? Don’t let obstacles like these stop you anymore. Try some workarounds.

• If it’s cold outside: It’s generally safe to exercise when the mercury is above 32° F and the ground is dry. The right gear for cold doesn’t need to be fancy. A warm jacket, a hat, gloves, heavy socks, and nonslip shoes are a great start. Layers of athletic clothing that wick away moisture while keeping you warm can help, too. Consider going for a brisk walk or hike, taking part in an orienteering event, or working out with battle ropes ($25 and up) that you attach to a tree.
• If you have mobility issues: Most workouts can be modified. For example, it might be easier to do an aerobics or weights workout in a pool, where buoyancy makes it easier to move and there’s little fear of falling. Or try a seated workout at home, such as chair yoga, tai chi, Pilates, or strength training. You’ll find an endless array of free seated workout videos on YouTube, but look for those created by a reliable source such as Silver Sneakers, or a physical therapist, certified personal trainer, or certified exercise instructor. Another option is an adaptive sports program in your community, such as adaptive basketball.
• If you can’t stand formal exercise: Skip a structured workout and just be more active throughout the day. Do some vigorous housework (like scrubbing a bathtub or vacuuming) or yard work, climb stairs, jog to the mailbox, jog from the parking lot to the grocery store, or do any activity that gets your heart and lungs working. Track your activity minutes with a smartphone (most devices come with built-in fitness apps) or wearable fitness tracker ($20 and up).
• If you’re stuck indoors: The pandemic showed us there are lots of indoor exercise options. If you’re looking for free options, do a body-weight workout, with exercises like planks and squats; follow a free exercise video online; practice yoga or tai chi; turn on music and dance; stretch; or do a resistance band workout. Or if it’s in the budget, get a treadmill, take an online exercise class, or work online with a personal trainer. The American Council on Exercise has a tool on its website to locate certified trainers in your area.

Is it hard to find time to exercise?

The good news is that any amount of physical activity is great for health. For example, a 2022 study found that racking up 15 to 20 minutes of weekly vigorous exercise (less than three minutes per day) was tied to lower risks of heart disease, cancer, and early death.

"We don't quite understand how it works, but we do know the body's metabolic machinery that imparts health benefits can be turned on by short bouts of movement spread across days or weeks," says Dr. Aaron Baggish, founder of Harvard-affiliated Massachusetts General Hospital's Cardiovascular Performance Program and an associate professor of medicine at Harvard Medical School.

And the more you exercise, Dr. Baggish says, the more benefits you accrue, such as better mood, better balance, and reduced risks of diabetes, high blood pressure, high cholesterol, and cognitive decline.

What’s the next step to take?

For most people, increasing activity is doable. If you have a heart condition, poor balance, muscle weakness, or you’re easily winded, talk to your doctor or get an evaluation from a physical therapist.

And no matter which activity you select, ease into it. When you’ve been inactive for a while, your muscles are vulnerable to injury if you do too much too soon.

“Your muscles may be sore initially if they are being asked to do more,” says Dr. Sarah Eby, a sports medicine specialist at Harvard-affiliated Spaulding Rehabilitation Hospital. “That’s normal. Just be sure to start low, and slowly increase your duration and intensity over time. Pick activities you enjoy and set small, measurable, and attainable goals, even if it’s as simple as walking five minutes every day this week.”

Remember: the aim is simply exercising more than you have been. And the more you move, the better.

About the Author

Heidi Godman, Executive Editor, Harvard Health Letter

Heidi Godman is the executive editor of the Harvard Health Letter. Before coming to the Health Letter, she was an award-winning television news anchor and medical reporter for 25 years. Heidi was named a journalism fellow … See Full Bio View all posts by Heidi Godman

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

At a dental appointment last month, I spotted a lead vest hanging unassumingly on the wall of the exam room as soon as I walked in. “Still there, but now obsolete,” I thought.

I’d just learned about new guidelines from the American Dental Association (ADA) saying lead vests and thyroid collars that cover the neck are no longer needed during dental x-rays. But they’d been a fixture of my dental experiences — including many cavities, four root canals, a tooth extraction, and two crowns — for my entire life. What changed, and could I feel safe without the vest?

Why were lead vests used in past years?

Lead vests and thyroid collars have been worn by countless Americans during dental x-rays over the years. They’ve been in use for far longer than my lifetime — about 100 years. The heavy apron-like shields are placed over sensitive areas, including the chest and neck, before the x-rays are taken.

“I haven’t worn a lead apron in the last 10 or 15 years — unless a dentist insists I put it on — because I know it isn’t needed,” says Dr. Bernard Friedland, an associate professor of oral medicine, infection, and immunity at Harvard School of Dental Medicine.

What has changed about dental x-rays?

When lead vests and thyroid collars were first recommended, x-ray technology was much less precise. But the technology has evolved significantly over the last few decades in ways that dramatically improve patient safety:

• Digital x-rays enable far smaller radiation doses, reducing radiation exposure and the risks associated with higher doses, such as cancer. “The doses used in dental radiology are negligibly small now. If you go to the dentist today for a full series of mouth x-rays that are taken with a digital sensor, the total exposure time is just over five seconds,” explains Dr. Friedland, an expert in oral radiology. “A hundred or so years ago, that exposure time would have been many minutes.”
• The small size of today’s x-ray beam significantly reduces radiation “scatter” and restricts the beam size to only the area needing to be imaged. This protects patients from radiation exposure to other parts of the body.

A less-recognized strike against using lead vests and thyroid collars is their ability to get in the way. They may block the primary x-ray beam, preventing dentists from capturing needed images. This quirk can lead to repeat imaging and unnecessary exposure to additional radiation. This is more likely to occur with panoramic x-rays.

The gear may also spread germs, Dr. Friedland notes. Although disinfected, it’s not sterilized between uses. “There’s a risk of spreading bacteria and viruses,” he says. “To me, that’s also an issue and another reason I don’t want to use one on myself.”

Who no longer needs the shields?

No one does — even children, who presumably have a long life of dental x-rays in front of them. The new recommendations apply to all patients regardless of age, health status, or pregnancy, the ADA says.

The recommendation to discontinue lead vests has been a long time in the making. In fact, the ADA isn’t the first professional organization to propose it. The American Association of Physicists in Medicine did so in 2019, followed by the American College of Radiology in 2021 and the American Academy of Oral and Maxillofacial Radiology in 2023.

Are some people confused or concerned about the no-lead-vest policy?

Yes. The new guidelines are bound to draw confusion and fear, Dr. Friedland says. Some people may even insist on continuing to wear a lead vest during x-rays.

“A big problem is that people’s perception of risk is very skewed,” he says. “Some people, you’ll never convince.”

People are likely to feel more comfortable if the practice is uniformly adopted by dentists. However, the ability to implement this change may hinge partly on public response. And it could take a while to fully adopt.

“I think the public is going to have more say on this than dentists,” Dr. Friedland says. “It might take a generation to make this change, maybe longer.”

Still concerned about the new recommendations?

If you have lingering concerns about the new recommendations, talk to your dentist.

And ask if dental x-rays are necessary to proceed with your diagnosis or treatment plan. Sometimes it’s possible to take fewer x-rays — such as bitewing x-rays of the upper and lower back teeth only — or to use certain types of imaging less frequently. Even with far safer x-ray conditions, dentists should be able to justify that the information from images is integral to diagnose problems or improve care, Dr. Friedland says.

It’s worth noting that the dose of radiation, while far lower than in the past, varies with the type of imaging and which parts of the jaw are being imaged. For example, the digital dental x-rays mentioned above involve less radiation than conventional dental x-rays. Either panoramic dental x-rays, or 3-D dental x-rays taken with a CBCT system that rotates around the head, typically involve more radiation than conventional dental x-rays.

Whenever possible, dentists should use images taken during previous dental exams, according to the ADA. “If I don’t need an x-ray, I don’t get one,” says Dr. Friedland. “I’m not cavalier about it. I also use technical parameters that keep the x-ray dose as low as reasonably possible.”

About the Author

Maureen Salamon, Executive Editor, Harvard Women's Health Watch

Maureen Salamon is executive editor of Harvard Women’s Health Watch. She began her career as a newspaper reporter and later covered health and medicine for a wide variety of websites, magazines, and hospitals. Her work has … See Full Bio View all posts by Maureen Salamon

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD

What is a drought?

A drought is a prolonged dry period without rain. In the last few decades, droughts are occurring more frequently worldwide.

With climate change, rising temperatures are making many regions dry within the US and beyond. Here’s how to recognize potential harms if drought has a grip where you live, and actions you can take to stay healthy.

How do droughts affect our world?

The downstream effects of droughts on the planet and our health are complex. One example is water shortages, which can harm crops, livestock, and aquatic life. This compromises food supplies, drives up prices, and worsens food insecurity and malnutrition. Trees, which offer shade during hot weather and help counter climate change, may die during severe droughts. Droughts are making some parts of the world uninhabitable, leading to climate migration.

How can droughts harm health?

There are many ways, big and small, through which dryer conditions harm health.

Droughts play a role in diseases

During droughts, lower water flow leads to stagnation. This can

• increase the concentration of health-harming water pollutants in streams, rivers, and reservoirs
• contribute to harmful algal blooms that can cause skin or gastrointestinal problems
• offer breeding grounds for mosquitoes that carry diseases.

And as water levels drop, the water also becomes warmer. This can foster the growth of pathogens (like some viruses, protozoa, and bacteria). If your drinking water is from a private well, this may be a particular concern for you.

Also, farmers may be more likely to use recycled water for irrigation during droughts. This may lead to more infectious agents like E. coli or Salmonella harbored on crops.

Droughts contribute to poor air quality

The dry conditions during droughts lend themselves to wildfires. That’s an immediate threat to local communities, but also can send harmful wildfire smoke to more distant regions, depending on wind patterns.

Droughts can also lead to dust storms that carry and transport microorganisms, allergens like pollen, and other polluting particulate matter. This can increase the risk of infections, like Valley fever, and worsen respiratory illnesses, such as asthma, chronic obstructive pulmonary disease (COPD), and other lung conditions.

One more challenge is reduced availability of the renewable hydropower energy. Dry periods often coincide with high temperatures. The increased energy demand may require utilities to shift to using more-polluting fossil fuel sources, which further increases the greenhouse gas emissions that cause climate change.

We can all take steps to keep the air we breathe healthier — whether or not drought is contributing to worse air quality where we live.

What can we do to lessen the impact of droughts?

Around the planet, groundwater is stored in natural spaces called aquifers. As overused groundwater aquifers dry up due to drought combined with demands from people and agriculture, more countries face water scarcity. There is growing interest in solutions like treating wastewater for reuse and in desalination of ocean water, though these alternatives come with their own challenges.

To address the drought problem, the US has created the National Integrated Drought Information System (NIDIS) to coordinate research, drought monitoring, and a drought early warning system.

What actions can you take to stay healthy during a drought?

• Stay hydrated. But also stay informed on the quality of your drinking water, especially if you rely on well water. You can contact local water authorities for information on public water quality.
• Check for local advisories on harmful algal blooms before going in the water to swim or allowing pets to swim.
• Follow your local air quality on AirNow.gov, which offers daily information on local air quality. The site also tracks wildfires, and offers guidance on when to minimize your time outdoors and downloadable guides to protect yourself when air quality is unhealthy.
• Be careful about recreational water activities like boating and diving during droughts when the water level may be down.
• Follow Smokey Bear’s advice on how to prevent wildfires.
• If your community is experiencing a drought and water shortage, the Environmental Protection Agency (EPA) provides some tips on home water conservation. But even during water shortages, it is important to not skip hand hygiene and washing fruits and vegetables. And if you are using a rain barrel to conserve water, using a fine mesh screen can help keep away mosquitoes (which only need a teaspoon of water to lay their eggs).

About the Author

Wynne Armand, MD, Contributor

Dr. Wynne Armand is a physician at Massachusetts General Hospital (MGH), where she provides primary care; an assistant professor in medicine at Harvard Medical School; and associate director of the MGH Center for the Environment and … See Full Bio View all posts by Wynne Armand, MD