Going to bed regularly by 10-11 pm is associated with better heart health and reduced risk of heart disease compared to earlier or later bedtimes.
This is according to a new research work published today in European Heart Journal – Digital Health, a journal of the European Society of Cardiology (ESC).
The authors behind the research explained that alignment of bedtime to the body’s 24-hour internal clock, called circadian rhythm, can reduce the risk of heart attacks and strokes.
The researchers examined 88,026 participants in the UK Biobank recruited between 2006 and 2010. The average age was 61 years (range 43 to 79 years) and 58% were women.
They collected data from the participants on sleep onset and waking up time over seven days using a wristwatch-like device worn by the participants. Other information collected included demographic, lifestyle, health and physical assessment of each participant.
The scientists then monitored heart and circulatory health of the participants over an average of six years. Specifically, they took note of how many of the participants developed new cardiovascular disease, mostly heart attacks and strokes over the period.
The results showed that 3,172 participants (3.6%) developed cardiovascular disease and many of these cases occurred in people who went to bed later or earlier than 10pm to 11pm.
Compared to sleep onset from 10:00 to 10:59 pm, there was:
– 25% higher risk of cardiovascular disease with a sleep onset at midnight or later,
– 12% greater risk for 11:00 to 11:59 pm, and
– 24% raised risk for falling asleep before 10:00 pm.
– In a further analysis by sex, the association with increased cardiovascular risk was stronger in women, with only sleep onset before 10:00 pm remaining significant for men.
The link remained even after adjustment for sleep duration and sleep irregularity.
The researchers also adjusted for other factors known to influence cardiovascular risk such as age, sex, weight, cholesterol levels, blood pressure and smoking status.
Study author Dr David Plans, from the University of Exeter, 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.”
On the possible reasons for the observed stronger association between sleep onset and cardiovascular disease in women, 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.”
“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,” Dr Plans concluded.
Speaking to the BBC News, Regina Giblin, senior cardiac nurse at the British Heart Foundation, said: “This large study suggests that going to sleep between 10 and 11pm could be the sweet spot for most people to keep their heart healthy long-term.”
“However, it’s important to remember that this study can only show an association and can’t prove cause and effect. More research is needed into sleep timing and duration as a risk factor for heart and circulatory diseases.”
Previous research works have found that getting enough sleep is important for our general wellbeing as well as our heart and circulatory health. Experts recommend that healthy adults should aim for seven to eight hours of sleep per night.