Going to sleep between 10pm and 11pm is associated with a lower risk of developing cardiovascular disease, according to a study recently published in the European Heart Journal.

The study, which was based on the data of more than 88,000 individuals in the UK Biobank, examined the association between objectively measured sleep onset.

While many studies have investigated the link between sleep duration and cardiovascular disease, few have explored the relationship between sleep timing and heart disease.

Those who went to bed after midnight had a 25% higher risk of cardiovascular disease

Data on sleep onset and waking up time were collected over seven days using a wrist-worn accelerometer. Participants completed demographic, lifestyle, health and physical assessments and questionnaires and were then followed up for a new diagnosis of cardiovascular disease.

During an average follow-up of 5.7 years, 3,172 (3.6%) developed cardiovascular disease, with incidence highest in those with sleep times at midnight or later and lower in those with sleep onset between 10pm and 11pm.

The researchers found that those who went to bed after midnight had a 25% higher risk of cardiovascular disease compared to those who went to bed between 10pm and 11pm, while those who went to bed between 11pm and midnight had a 12% higher risk.

Early bed times were also associated with a higher risk of cardiovascular disease, with those going to bed before 10pm having a 24% higher risk.

Early or late bedtimes disrupt the internal body clock

Study author Dr. David Plans of the University of Exeter said the findings suggest that early or late bedtimes disrupt our internal body clock, which has adverse consequences on heart health.

The results suggest that the optimum time to go to sleep is at a specific point in the body’s 24-hour cycle, which appears to be between 10pm and 11pm.

Dr. Plans says the high risk of cardiovascular disease associated with going to sleep after midnight could be because a late bedtime reduces the likelihood of seeing morning light, which resets the body clock.

“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,” he concluded.