Research involving more than 88,000 participants from the UK Biobank indicates that falling asleep between 10pm and 11pm is associated with a lower risk of developing cardiovascular disease. The study, published in the European Heart Journal – Digital Health, found that those who nod off at midnight or later have a 25% higher risk, while those who fall asleep before 10pm face a 24% increased risk compared with those who sleep in the golden hour.
The analysis, led by Dr David Plans of Huma Therapeutics and the University of Exeter, used data from wrist devices worn by participants for seven days. Over an average follow-up of 5.7 years, 3,172 of the 88,026 participants developed cardiovascular disease. After adjusting for factors such as age, sex, smoking, sleep duration, diabetes, blood pressure, and socioeconomic status, the 10pm-11pm bedtime window emerged as the sweet spot.
Dr Plans noted that early or late bedtimes may disrupt the body’s internal clock by causing individuals to miss morning daylight cues. This misalignment can increase inflammation and impair glucose regulation, potentially raising cardiovascular risk. However, he stressed that the study cannot prove causation, as sleep timing may be linked to other health behaviours like drinking.
The association appeared stronger in women, though the reasons remain unclear. The researchers acknowledged limitations, including the predominantly white sample aged 43-79. Plans said further studies with larger and more diverse groups are needed before prescribing specific bedtimes to the public. He added that the findings underscore the importance of sleep hygiene in cardiovascular health.
