Sleeping between 10pm and 11pm has been linked to reducing the risk of heart disease when compared to earlier and later bedtimes, according to a new study.

Study author, Dr David Plans from the University of Exeter said: “The body has a 24-hour internal clock, called circadian rhythm, that helps regulate physical and mental functioning.

“While we cannot conclude causation from our study, the results suggest that early or late bedtimes may be more likely to disrupt the body clock, with adverse consequences for cardiovascular health.”

The connection between how much sleep you get, and your risk of cardiovascular disease has been explored by numerous studies, yet the link between the timing of sleep and heart disease has little research.

The new research involved 88,026 participants aged from 43 to 79, with an average of 61-years-old, between 2006 and 2010. The participants’ sleep onset (when the participant fell asleep) and the time they woke was accurately measured over a week.

During the trial, the participants also completed lifestyle, health, demographic, and physical assessments. Researchers then followed up with participants for a diagnosis of cardiovascular disease five years later.

Results showed that 3.6 per cent of participants had been diagnosed with cardiovascular disease. It was found that participants who went to sleep at midnight or later were more likely to develop cardiovascular disease, and less likely in those who went to sleep between 10pm and 10:59pm.

When compared to going to sleep between 10pm to 10:59pm, researchers found that the risk of cardiovascular disease was:

  • 25 per cent more with a sleep onset of midnight or later
  • 12 per cent more with a sleep onset of 11pm to 11:59 pm
  • 24 per cent more with a sleep onset before 10pm

More than 50 per cent of the participants were female and the results showed that women were more likely to have an increased risk of cardiovascular disease. Going to sleep before 10pm was only significant for men, the findings identified.

Dr Plans summarised: “Our study indicates that the optimum time to go to sleep is at a specific point in the body’s 24-hour cycle and deviations may be detrimental to health.

“The riskiest time was after midnight, potentially because it may reduce the likelihood of seeing morning light, which resets the body clock.”

Highlighted that the stronger link between cardiovascular disease and sleep onset in women was not clear, Dr Plans said: “It may be that there is a sex difference in how the endocrine system responds to a disruption in circadian rhythm.

“Alternatively, the older age of study participants could be a confounding factor since women’s cardiovascular risk increases post-menopause – meaning there may be no difference in the strength of the association between women and men.”

He added: “While the findings do not show causality, sleep timing has emerged as a potential cardiac risk factor – independent of other risk factors and sleep characteristics.

“If our findings are confirmed in other studies, sleep timing and basic sleep hygiene could be a low-cost public health target for lowering risk of heart disease.”

The study was published in the European Heart Journal – Digital Health.

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