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Tuesday 19th June 2018

Seven hours is best sleep length

2nd August 2010

Seven hours is the best amount of sleep to have in a night, with both more and less than that resulting in a higher risk of cardiovascular problems, a US study has shown.


The researchers found that people who slept less than five hours a day had twice the risk of developing angina, coronary heart disease, heart attack or stroke.

Anoop Shankar, associate professor at West Virginia University's department of community medicine, who led the study on sleep and cardiovascular health, said doctors should screen their patients for changes in sleep duration, when assessing their risk of heart disease.

In a separate, related study, David Dinges, head of the sleep and chronobiology unit at the University of Pennsylvania school of medicine, said that people who had not slept enough during the week would not be able to "catch up" on sleep easily at the weekend.

In a study of 159 participants, subjects still scored poorly in measures of attention span and reaction times once they had been allowed a 10-hour catch-up sleep, suggesting that several nights of catch-up sleep might be needed.

The West Virginia researchers also found that people who slept more than nine hours a day were one-and-a-half times more likely to develop cardiovascular disease than people who got about seven hours of sleep.

Subjects under 60 who slept less than five hours a night were three times more likely to develop cardiovascular disease than people who slept seven hours per night.

In the study led by Dinges on chronic sleep deprivation, which the researchers called one of the largest sleep deprivation experiments ever, 142 adults were asked to sleep only four hours per night on five consecutive nights.

The average age of the study participants in that study was 30.

The study subjects were then given 'doses' of recovery sleep after their week of sleep deprivation.

As a control, the researchers allowed another 17 participants to sleep at most 10 hours per night.

The researchers then tested the study subjects for wakefulness.

For the study on sleep and cardiovascular health, the researchers polled about 30,000 people about their sleep habits and made statistical analyses, taking socio-economic differences into account.

Past studies have also shown that there is a link between sleep duration, hormone levels, and metabolism, suggesting a reason why cardiovascular health and sleep patterns seem to be linked.

In that study, women who got five hours or fewer of sleep, including naps, were more than two-and-a-half times as likely to develop cardiovascular disease.

The researchers said that sleeping too little was associated with angina, while oversleeping was just as linked to heart attack and stroke as sleeping too little.


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