Month: December 2022

We can feel groggy when our sleep schedule is thrown off even just a little. So what happens when shift work requires people to regularly stay awake through the night and sleep during the day — and how can they protect their health and well-being?

What is shift work disorder?

Mounting evidence, including several new studies, paints a worrisome picture of the potential health fallout of nontraditional shift work schedules that affect 15% to 30% of workers in the US and Europe, including factory and warehouse workers, police officers, nurses, and other first responders.

So-called shift work disorder mainly strikes people who work the overnight or early morning shift, or who rotate their shifts, says Eric Zhou, an assistant professor in the Division of Sleep Medicine at Harvard Medical School. It is characterized by significant problems falling and staying asleep, or sleeping when desired. That’s because shift work disrupts the body’s normal alignment with the 24-hour sleep-wake cycle called the circadian rhythm.

“People who work 9-to-5 shifts are typically awake when the sun is up, which is aligned with their body’s internal circadian clock. But for shift workers, their work hours and sleep hours are misaligned with the natural cues to be awake or asleep,” Zhou says. “They’re working against the universe’s natural inclinations — not just their body’s.”

What’s the connection between shift work and health?

A 2022 research review in the Journal of Clinical Sleep Medicine links shift work to higher risks for serious health problems, such as heart attack and diabetes. This research suggests adverse effects can include metabolic syndrome (a cluster of conditions that raises the risks for heart disease, diabetes, and stroke), accidents, and certain types of cancer.

“The research is consistent and powerful,” Zhou says. “Working and sleeping during hours misaligned with natural light for extended periods of time is not likely to be healthy for you.”

How do new studies on shift work boost our understanding?

New research continues to add to and strengthen earlier findings, teasing out specific health effects that could stem from shift work.

• Shift workers on rotating schedules eat more erratically and frequently than day workers, snack more at night, and consume fewer healthier foods with potentially more calories, a study published online in Advances in Nutrition suggests. This analysis reviewed 31 prior studies involving more than 18,000 participants, comparing workers’ average food intake over 24 hours.
• Disrupting the circadian rhythm through shift work appears to increase the odds of colorectal cancer, a malignancy with strong ties to lifestyle factors, according to a 2023 review of multiple studies published online in the Journal of Investigative Medicine. Contributors to this higher risk may include exposure to artificial light at night, along with complex genetic and hormonal interactions, study authors said.

“Cancer understandably scares people, and the World Health Organization recognizes that shift work is a probable carcinogen,” Zhou says. “The combination of chronically insufficient and poor-quality sleep is likely to get under the skin. That said, we don’t fully understand how this happens.”

How can you protect your sleep — and your health?

If you work overnight or early morning shifts, how can you ensure you sleep more soundly and restfully? Zhou offers these evidence-based tips.

Time your exposure to bright and dim light. Graveyard shift workers whose work schedule runs from midnight through 8 a.m., for example, should reduce their light exposure as much as possible after leaving work if they intend to go right to sleep once they return home. “These measures could take the form of wearing blue light–blocking glasses or using blackout shades in your bedroom,” he says.

Make enough time for sleep on days off. “This is often harder than it sounds, because you’ll want to see your family and friends during nonwork hours,” Zhou says. “You need to truly protect your opportunity for sleep.”

Maintain a consistent shift work schedule. “Also, try to minimize the consecutive number of days you spend working challenging shifts,” he says.

Talk to your employer. Perhaps your boss can schedule you for fewer overnight shifts. “You can also ask your doctor to make a case for you to be moved off these shifts or have more flexibility,” Zhou says.

Look for practical solutions that allow you to get more restful sleep. “People engaged in shift work usually have responsibilities to their job as well as their family members, who often operate under a more typical 9-to-5 schedule,” he notes. “The goal is to preserve as strong a circadian rhythm as possible under the abnormal schedule shift work requires.”

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

Are you having a little trouble hearing conversations? If so, you’re not alone. An estimated 23% of Americans ages 12 and older have hearing loss. Although most of those people have mild hearing loss, for people ages 80 years and older, it’s more common for hearing loss to be moderate to severe than mild.

But not only is moderate to severe hearing loss disruptive to one’s life, it also makes you more likely to develop dementia. A new study helps explain why — and what you can do about it.

What did the new study look at and find?

A study published in JAMA focused on a sample of adults in the United States from the National Health and Aging Trends Study, which follows Medicare beneficiaries. The participants sampled were 70 or older.

The researchers found that about 33% of participants had normal hearing, 37% had mild hearing loss, and 30% had moderate to severe hearing loss. Dementia occurred least often among those with normal hearing (6%), more often among those with mild hearing loss (9%), and most often among those with moderate to severe hearing loss (17%). That’s a large increase in risk, particularly for those whose hearing loss is moderate to severe.

What else to know about this study

The study sample was selected to make it possible to analyze subgroups by age and apply findings to a diverse population. The sample included additional participants ages 90 years and older, and additional participants who identified as Black. Of the 2,413 total participants, 53% were ages 80 years and older, 56% were female, 19% were non-Hispanic Black, 4.5% were Hispanic, and 74% were non-Hispanic white.

Also, unlike previous research, this study looked objectively at hearing loss and dementia. Prior research had shown that hearing loss is thought to account for about 8% of all dementia cases worldwide. Exactly why the connection exists is not known.

It’s important to note that most large studies that found this link were based on questionnaires that people fill out. In other words, no one actually measured the hearing of those participating in the study to make sure that they had hearing loss — or that their hearing was really normal.

In this new study, however, the investigative team used an electronic tablet-based audiometer to evaluate participants’ hearing for four pure tone frequencies that are most important for understanding speech. So, for the first time in a large study, there was objective measurement of hearing loss.

How do hearing aids reduce the risk of dementia?

If you have hearing loss, does that mean you’re doomed to develop dementia? Not at all. This study found that those with moderate to severe hearing loss could significantly reduce their risk of dementia simply by using hearing aids.

This research helps us understand why hearing loss causes dementia. Here’s the connection:

There is increasing evidence that the more the brain is stimulated, the less likely it is that dementia will develop. When there is hearing loss, auditory stimulation is reduced. This, by itself, likely increases dementia risk. But even more important is that when an individual suffers from moderate to severe hearing loss, they are less likely to participate in social activities. Perhaps they are embarrassed about their hearing loss. Or they may simply find it unrewarding to attend a social event when they cannot hear what is going on.

It turns out that social activities are one of the best ways to stimulate the brain, as there is evidence that our brains evolved to facilitate social behavior. Given all this information, you won’t be surprised to learn that reduced social activity has been linked to cognitive decline. Thus, this new study provides additional evidence that the reason hearing loss increases the risk of dementia is because hearing loss reduces brain stimulation — both directly and through reduced social interaction.

What to do if you have hearing loss

Don’t let hearing loss raise your risk of dementia.

• Keep your ears clean. (But remember, never put anything in your ears smaller than your elbow. Ask your doctor if you’re not sure how to clean your ears.)
• If you can’t hear and you don’t have hearing aids, get them. Hearing aids now available over the counter can help many people with mild to moderate hearing loss.
• If you have hearing aids, wear them.
• If your hearing aids aren’t working, get them fixed.
• Don’t be passive — ramp up your social life and other activities.

All these things will help to reduce your risk of dementia. And you might just find that, despite some hearing loss, you’re enjoying life more.

About the Author

Andrew E. Budson, MD,

Contributor; Editorial Advisory Board Member, Harvard Health Publishing

Dr. Andrew E. Budson is chief of cognitive & behavioral neurology at the Veterans Affairs Boston Healthcare System, lecturer in neurology at Harvard Medical School, and chair of the Science of Learning Innovation Group at the … See Full Bio View all posts by Andrew E. Budson, MD