Scientists could have found the perfect bedtime to keep hearts healthy


Many of us feel we’re never getting enough sleep; blaming young children, snoring partners, stresses of life or uncomfortable pillows.

Scientists in Europe have said that research into the links between sleep and heart health often rely on foggy recollections or unreliable sleep diaries. Now, by attaching wrist-worn accelerometer devices to more than 88,000 people, they have been able more accurately to monitor sleep patterns and say they could have found an optimal bedtime to keep hearts healthy.

Going to sleep between 10 p.m. and 11 p.m. is associated with a lower risk of developing heart disease in comparison with earlier or later bedtimes, according to a study published Tuesday in the European Heart Journal — Digital Health.

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“We can’t help what we’ve evolved to be. We’ve evolved to be daytime creatures … that don’t live at night,” study author David Plans, the head of research at Huma, a British health-care technology company, told The Washington Post. “The circadian clock has a much stronger influence on overall health than we thought.”

The body’s natural clock is responsible for setting the rhythm of our metabolism, learning and emotions, and “without it we’re a mess,” Plans said. He underscored that those who sleep late or work night shifts and unusual hours shouldn’t lament but should ensure they expose their eyes to “full spectrum light” in the mornings.

“That central clock, which is calibrated by exposure to light needs recalibrating … when that’s missed the knock-on effects can be really detrimental,” he added.

The relationship between sleep timing and heart disease has been relatively underexplored, the study found, but “growing evidence suggests that poor sleep health is associated with cardiovascular risk.” It also found that the risk may be more pronounced in women but said more research was needed. Plans said the gender difference was a “surprising finding” of the research and could be linked to the hormonal impact of the menopause or endocrine differences between genders.

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The study looked at 88,026 individuals in Britain between 2006 and 2010 — around 58 percent were female and the average age was 61. The researchers also looked at factors such as smoking, diabetes, high cholesterol and whether participants self-identified as early birds or night owls in their sleeping habits.

Data on falling-asleep and waking-up times was collected over seven days using the wrist-worn accelerometers. The study found that around 3,172 participants (3.6 percent) developed cardiovascular diseases — such as a heart attack, stroke or narrowed heart arteries. The rate of occurrences was highest in those with sleep times at midnight or later and lowest in those who fell asleep between 10 p.m. and 10:59 p.m.

There was a 25 percent higher risk of cardiovascular disease among those who fell asleep at midnight or later vs. those who fell asleep between 10 p.m. and 10:59 p.m. and a 24 percent raised risk if falling asleep before 10 p.m., the research found.

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Plans said the coronavirus pandemic had probably impacted people’s sleeping habits, with more of us waking up later, working from home and therefore not leaving our homes to commute or expend energy — and then having trouble falling asleep at night. “It’s a self-perpetuating cycle,” he said. Fixing sleep patterns also has “enormous” benefits to mental health disorders, he added.

Cardiovascular diseases continue to be the leading causes of death worldwide, with an estimated 18 million deaths each year, according to the World Health Organization. More than four out of five deaths are due to heart attacks and strokes, and one-third occur in people under 70.

Heart disease is the leading cause of death for men and women broadly, and for people of most racial and ethnic groups in the United States, according to the Centers for Disease Control and Prevention. About 659,000 people in the United States die of heart disease each year, accounting for around 1 in 4 deaths. Better “sleep timing” could be “a low-cost public health target for lowering risk of heart disease,” Plans added.

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Healthful sleep requires adequate duration, good quality, regularity and the absence of sleep disturbances, says the American Academy of Sleep Medicine, which recommends that adults regularly sleep seven hours or more per night to promote optimal health. About 70 million Americans experience sleep disorders each year, including insomnia and sleep apnea, which can be linked to shift work, jet lag or medical conditions.

A separate U.S. study published this year also found what is called a sleep gap, with those who are poor, as well as socially disadvantaged racial minorities, sleeping much less well on average than the rich. Inadequate sleep among low-income adults and racial minorities also contributed to higher rates of illnesses, including dementia. Sleep deprivation also has been linked to hypertension, obesity and diabetes.