Disrupted Sleep

How disrupted sleep may lead to heart disease

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At a Glance

  • Researchers found that sleep disruption activates a molecule that triggers inflammation and leads to fatty buildup in mouse arteries.
  • The findings underscore the importance of getting enough quality sleep to maintain heart health. It also suggests new targets for fighting heart disease.

Plaque in artery

Plaque within an artery of a mouse that had a normal sleeping pattern, top. There is significantly more plaque in the artery of a mouse with disrupted sleep,

Heart disease is the leading cause of death among women and men in the United States. The most common cause of heart disease is when fatty deposits called plaque build up inside your arteries, the blood vessels that carry oxygen-rich blood around your body. This is called atherosclerosis. White blood cells from the immune system collect at the plaque and cause inflammation.

Over time, the plaque hardens and narrows your arteries. This limits the flow of oxygen-rich blood to your heart and other organs. Atherosclerosis can lead to serious problems, including heart attack, stroke, or even death.

Recent research has linked sleep deficiency and certain sleep disorders, such as sleep apnea, to an increased risk of heart disease and other health conditions. But the molecular mechanisms underlying the link between sleep and heart disease has been unclear.

To learn more about the impact of sleep deficiency on heart disease, a team led by Dr. Filip Swirski at Harvard Medical School and Massachusetts General Hospital studied a group of mice that were genetically engineered to develop atherosclerosis. The research was supported in part by NIH’s National Heart, Lung, and Blood Institute (NHLBI). Results were published online on February 13, 2019, in Nature.

The researchers repeatedly disrupted the sleep cycles of half the mice, and the other half slept normally. After 16 weeks, the sleep-disrupted mice developed larger arterial plaques than the mice with normal sleep patterns.

The sleep-disrupted mice also had twice the level of certain white blood cells in their circulation than the control mice. And they had lower amounts of hypocretin, a hormone made by the brain that plays a key role in regulating sleep and wake states (also known as orexin). Further experiments showed that hypocretin suppressed the production of stem cells that make the white blood cells in their bone marrow.

Sleep-deficient mice that received hypocretin supplementation tended to produce fewer immune cells and develop smaller artery wall plaques than mice that weren’t given the supplementation. These results suggest that hypocretin loss during disrupted sleep contributes to inflammation and atherosclerosis.

“We’ve identified a mechanism by which a brain hormone controls production of inflammatory cells in the bone marrow in a way that helps protect the blood vessels from damage,” Swirski explains. “This anti-inflammatory mechanism is regulated by sleep, and it breaks down when you frequently disrupt sleep or experience poor sleep quality. It’s a small piece of a larger puzzle.”

“This appears to be the most direct demonstration yet of the molecular connections linking blood and cardiovascular risk factors to sleep health,” says Dr. Michael Twery, director of NHLBI’s National Center on Sleep Disorders Research.

If disrupted sleep proves to have similar effects in people, these findings could open new avenues for developing ways to treat heart disease.

Disrupted sleep in your 30s-40s may impact memory later in life

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Researchers say the quality of sleep in younger years can impact memory in older age. Maria Korneeva/Getty Images

  • Sleep disruptions – waking up and then going back to sleep during the night – may contribute to memory and cognitive problems.
  • The duration of sleep was not considered in the study.
  • Researchers reported that cognitive issues showed up 10 years after the end of the study.

People who experience disrupted sleep in their 30s and 40s are more likely to have memory and cognitive problems later in life, according to a study published in Neurology, the journal of the American Academy of Neurology.

Researchers looked at the sleep patterns of 526 people who were followed for 11 years.

To calculate averages, the participants wore a wrist monitor for three consecutive days, one year apart. They also reported bedtimes and wake times in a sleep diary.

In addition, the partcipants completed a sleep quality survey, receiving a score ranging from 0 to 21, with higher scores indicating poorer sleep quality.

The scientists also recorded how long each person slept each night.

Participants also completed a series of memory and thinking tests.

Details from the study on sleep and memory

The study included 526 participants with an average age of 40 at baseline who were followed for 11 years. Of these, 239 people, or 46%, reported poor sleep, which was defined as having a sleep score of greater than 5.

Researchers also looked at:

  • Sleep fragmentation, repetitive short interruptions of sleep
  • The percentage of time spent moving
  • The percentage of time not moving for one minute or less

The scientists added the two percentages to determine an average sleep fragmentation score. Overall, the participants had an average sleep fragmentation score of 19%. The researchers then grouped the participants based on their scores.

The researchers reported that of the 175 participants with the most disrupted sleep, 44 had poor cognitive performance 10 years after the study ended, compared to 10 of the 176 with the least disruptive sleep.

The scientists noted that after adjusting for age, gender, race, and education, the people with the most disruptive sleep were more than twice as likely to have poor cognitive performance as those with the least disruptive sleep.

They also found no differences in cognitive performance in the middle group compared to those with the least disruptive sleep.

The length of time people slept and self-reported sleep quality were not associated with cognition in middle age.

Reaction to the memory and sleep study

“This important work shows how healthy brain aging is a lifelong endeavor,” says Dr. David Merrill, a geriatric psychiatrist and director of the Pacific Neuroscience Institute’s Pacific Brain Health Center in California who was not involved in the study.

“Even in early adulthood, sleep quality results in measurable changes in cognitive performance by mid-life. The study findings support the importance of sleep quality, uninterrupted, or unfragmented sleep in relation to cognitive performance,” Merrill told Medical News Today.

“Undoubtedly, we need a certain minimal quantity of sleep too, but the study wasn’t a sleep lab study, so it wasn’t structured to ask that question,” Merrill added. “Perhaps [discussing sleep patterns with my patients and] encouraging them to use sleep trackers so they can see for themselves how better sleep quality relates to days with improved energy and thinking. There are great direct-to-consumer wearables now that can allow us to know how well we’re doing to get a good quality night’s sleep.”

The researchers reported that the most significant limitation of the study was its small sample size. This prevented the researchers from thoroughly investigating potential race or gender differences.

How sleep and memory are connected

“This is a very interesting study,” said Dr. Steven Feinsilver, the director of the Center for Sleep Medicine at Northwell Lenox Hill Hospital in New York who was not involved in the study.

“We all know that sleep is good for you and the results of this study are undoubtedly true. But the question is, what came first: Did poor sleep quality cause cognitive dysfunction or did cognitive dysfunction cause poor sleep quality?,” Feinsilver asked.

“Everyone wakes up during the night, but most people don’t remember. We have what is called retrograde amnesia – the last few minutes before falling asleep doesn’t make it into our long-term memory,” Feinsilver told Medical News Today. “This is also true of waking during the night. If we wake up and quickly go back to sleep – which is very common – we don’t remember it.”

“There is still a lot that we don’t know about sleep,” he added. “But the most important aspect is – how do you feel the next day? If you typically feel good during the day, you probably get enough sleep. The average person needs about 7.25 hours, but this is an average. Some may need more; some may need less. People aren’t very good at assessing their own sleep, but they can assess how they feel during the day.”

Finding a balance between quantity and quality of sleep

It is possible that cognitive function is related more to the quality of sleep rather than the length of time spent sleeping.

A studyTrusted Source completed in 2021 at Washington University Sleep Medicine Center reported that there could potentially be a middle range where cognitive function remained steady.

The scientists found that too little and too much sleep could contribute to cognitive difficulties. Cognitive scores declined in participants who slept less than 4.5 hours or more than 6.5 hours. The association held true even after adjusting for a variety of factors, including age, sex, and levels of Alzheimer’s proteins.

People who wake up feeling rested should not feel compelled to change their sleep habits, experts say.

However, those who do not sleep well might notice they have more difficulty with cognitive tasks. Treating the issue can potentially improve cognition.

New Parents May Face Up to Six Years of Disrupted Sleep

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It’s no secret that parents of new babies don’t get much sleep: infants have a wonky internal clock and frequent feeding needs, meaning that their moms and dads have to be available at all hours of the day and night. But as George Dvorsky reports for Gizmodo, an expansive new study has found that sleep deprivation may continue long after little ones come home from the hospital, with parents reporting less sleep and poorer sleep quality up to six years after the birth of their first child.

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Published in the journal Sleep, the study drew on data collected between 2008 and 2015 by the German Socio-Economic Panel, an ongoing study of private households in the country. The participants—2,541 women and 2,118 men—reported the births of a first, second or third child during the study period. To track sleep patterns over time, parents were asked during annual interviews to rate their sleep satisfaction on a scale between 0 and 10. They were also asked how many hours they sleep during an average working week day and an average weekend day.

Perhaps unsurprisingly, the researchers found that sleep satisfaction and duration among women decreased sharply after childbirth. New moms’ rating of their sleep quality dropped by 1.53 points on the assessment scale. They also reported getting 41 minutes less sleep after the birth of their first child, and 39 and 44 minutes less sleep after the births of their second and third children, respectively. Dads were also sleeping less, though the drop wasn’t as marked as it was among moms; they reported decreases in sleep duration of 14, 9 and 12 minutes after the births of their first, second and third children. Breastfeeding was linked with slight decreases in sleep satisfaction and duration among mothers.

When researchers took a closer look at the data, they found that sleep deprivation reached its peak in the three months after a baby was born. Between the third trimester of pregnancy and the first three months postpartum, sleep duration was 87 minutes shorter in women and 27 minutes shorter in men.

“It is possible that children’s increased fussing and crying during the first 3 months after birth, along with their dependence on frequent nocturnal feedings and other caretaking, are important reasons for parental sleep disturbance after childbirth,” the study authors note. “Apart from infant crying and frequent nursing, other potential proximate causes of poor postpartum sleep may involve physical pain following delivery and distress related to the demands of a new role.”

Parents tended to get more sleep after the three month mark, but between four and six years after the birth of their first child, moms and dads still hadn’t bounced back to pre-pregnancy levels of sleep satisfaction and duration. Again, the discrepancy was more pronounced among women, who rated their sleep quality 0.95 scale points lower than they did before their baby arrived, and reported getting 22 minutes less sleep, on average. Four to six years postpartum, dads’ sleep satisfaction was down by 0.64 scale points and their sleep duration was reduced by 14 minutes.

“We didn’t expect to find that,” Sakari Lemola, study co-author and associate professor of psychology at the University of Warwick, tells Nicola Davis of the Guardian. But he notes that there are “certainly many changes in [parents’] responsibilities” that might affect how well they are sleeping. Even kids who sleep through the night get sick and have nightmares, which inevitably means that their parents will get less shut-eye. Parenthood may also come with new worries that inhibit sleep, Lemola adds.

Interestingly, the researchers found that factors like parental age, household income and single versus joint parenting had little influence on how well mothers and fathers were sleeping. But the fact that women are more affected by postpartum sleep deprivation than men is revelatory. “This may be associated with the observation that mothers, including working women, still have more household and child rearing responsibilities and spend more time on these tasks compared with fathers in most industrialized countries including Germany,” the study authors write.

Understanding the nuances of sleep patterns among parents is important because sleep is a vital contributor to overall health. This is especially true of new mothers, since sleep problems have been linked to higher postpartum depression symptoms. The researchers say that the results of their study highlight the importance of giving new parents advice and support on managing sleep. There are things that can be done to mitigate the effects of sleep loss, like ensuring that the parent who will be handling most of the nighttime care gets a chance to rest in the evening.

“Try not to worry about non-essential jobs around the house,” Cathy Finlay, an prenatal teacher with the U.K.’s National Childbirth Trust, adds in an interview with Davis, “and accept help from family and friends when it’s offered.”