Month: July 2023

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

We’re bombarded with advertisements that tout all sorts of health benefits for vitamins and supplements, including improved memory. A May 2023 study of older adults suggests that a daily multivitamin can do just that — improve your memory enough such that it can function as if you were three years younger.

So, should you take that daily multivitamin? Let’s take a close look at the study.

Who took part in this multivitamin study?

This research is part of a larger study examining the effects of a multivitamin and/or cocoa (the main ingredient in chocolate) on cardiovascular and cancer outcomes. A prior sub-study found that a daily multivitamin improved thinking and memory — at least when evaluated with cognitive testing completed by phone.

For this study, 3,562 participants were willing and able to perform some tests of thinking and memory on a home computer. Half received a multivitamin; the other half received a placebo.

The participants identified as 93% white, 2.5% African American, and 1.4% Hispanic, so the results may not be generalizable. They were also well educated: more than half had completed college. In both groups, the average age was 71.

How did the researchers test memory?

The investigators evaluated the participants’ thinking and memory at baseline and after one, two, and three years.

For the memory test, participants were asked to memorize 20 words shown consecutively on a computer screen. Immediately after viewing these words, they had to type in as many words as they could remember (this was the primary measure of memory). Fifteen minutes later, they also typed in all the words they recalled (a secondary measure of memory).

Other secondary measures included:

• a novel object discrimination test (is this object the same or different from one recently shown?)
• an executive control test (in an array of nine arrows, is the central arrow red or blue?).

The participants repeated all of the tests one, two, and three years later.

What were the results of this study?

The two groups differed in immediate recall at year one:

• Those who took a placebo went from immediately recalling an average of 7.21 words at baseline to 7.65 words (a difference of 0.43 words)
• Those who took a daily multivitamin group went from 7.10 words at baseline to 7.81 words (a difference of 0.70 words).

This result was statistically significant. Additionally, these small effects held up at years two and three. By year three, the placebo group immediately recalled an average of 8.17 words and the multivitamin group immediately recalled 8.28 words.

No differences occurred between the two groups on secondary memory and executive function tests.

How can a multivitamin improve memory?

The authors note that low levels of vitamins B12 and D have been linked to cognitive decline and dementia. In a subset of participants who had their blood drawn, the levels of these vitamins did rise in the multivitamin group.

It seems plausible that a few of the 3,562 participants had low levels of these or other vitamins that are important for thinking and memory. In the placebo group, the few who had vitamin deficiencies would likely show less improvement in memory after their baseline tests, or a small decline. By contrast, those few participants in the multivitamin group with deficiencies would have them corrected by the supplements and, therefore, would perform relatively better.

Although this is just speculation, it would explain the small but seemingly real results — results that replicate the researchers' prior study, which used a telephone cognitive test to show thinking and memory benefit from a daily multivitamin.

It’s also worth noting that practice on memory tasks — the so-called practice effect — could contribute to small improvements shown from baseline to year one and year three.

Should you take a multivitamin to improve your memory?

The authors admitted that the effect of the multivitamin on immediate memory was small and may not be noticeable. However, they pointed out that this small effect could be important at the level of an entire population.

My opinion? You shouldn’t bother taking a multivitamin to try to improve your immediate recall of 20 words from 8.17 to 8.28 words. But it is worth speaking with your doctor about whether you could have a vitamin deficiency in B1, B6, B12, D, or any other important vitamins. I see several patients in my clinic every week who have startlingly low levels of vitamin D and B12. Your doctor may want to measure these levels. Or they may suggest simply taking a multivitamin daily.

If, after reading this article, you’ve decided to take a multivitamin, please check with your doctor or pharmacist about which one would be best for you. Make sure that they review any other vitamins, supplements, and medications you take to avoid rare but serious interactions.

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