Synchronising sleep to match our natural circadian rhythm is best for reduced risk of heart attack, strokes, and blood pressure, according to a study published in the European Heart Journal.
Researchers collected data on sleep and wake times over seven days in over 80,000 people and found that falling asleep between 11 pm to 11:59 pm meant a 12% greater risk for heart disease, compared to falling asleep between 10 pm and 11 pm.
Meanwhile, falling asleep before the recommended bedtime was also harmful, with a 24% increased risk if you fell asleep before 10 pm.
Falling asleep at midnight or later was associated with a 25% higher risk of cardiovascular disease.
The study saw just over 3,000 of the adults over an average of six years develop cardiovascular disease, with many of these cases occurring in people who go to bed later or earlier than the ideal bedtime.
Researchers also accounted for sleep duration and sleep irregularity or issues, and tried to combat other factors such as health, weight, diet and exercise, though they understood that not all circumstances could be mitigated, and their study cannot prove cause and effect.
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.’