Going to sleep between 10pm and 11pm is associated with a reduced risk of developing heart disease compared with earlier or later bedtimes, researchers report today.
A study published in European Heart Journal – Digital Health found there was a 25% higher risk of cardiovascular disease with a sleep onset at midnight or later, a 12% greater risk for 11pm-11.59pm, and a 24% raised risk for falling asleep before 10pm.
Study author Dr David Plans, of the University of Exeter, UK, said: “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 study included 88,026 people in the UK Biobank who were recruited between 2006 and 2010. The average age was 61 years and 58% of the participants were women.
Data on sleep onset and waking up time were collected over seven days, using a wrist-worn accelerometer, and participants also completed demographic, lifestyle, health and physical assessments and questionnaires.
During an average follow-up of 5.7 years, 3,172 participants (3.6%) developed cardiovascular disease and incidence was highest in those with sleep times at midnight or later and lowest in those with sleep onset from 10pm to 10:59 pm.
Dr Plans said: “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.”
However, the reasons for the stronger association between sleep onset and cardiovascular disease in women is unclear.
“It may be that there is a sex difference in how the endocrine system responds to a disruption in circadian rhythm,” said Dr Plans.
“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.
“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.”
Nikbakhtian S, Reed AB, Obika BD, et al. Accelerometer-derived sleep onset timing and cardiovascular disease incidence: a UK Biobank cohort study. Eur Heart J Digit Health 9 November 2021
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