People who go to bed at inconsistent times and sleep less than eight hours a night may be twice as likely to suffer major heart problems, according to a new study.
Researchers at the University of Oulu in Finland followed 3,231 adults for ten years to study how sleep patterns affect heart health.
Participants wore wearable devices that recorded when they went to bed, woke up, and the midpoint of sleep, which is the halfway point between falling asleep and waking.
To identify who had irregular sleep schedules, the researchers measured how much these times varied each day over seven consecutive days.
During the ten-year follow-up, 128 participants – about four per cent – experienced major heart events, including heart attack, stroke, unstable angina, hospitalisation for heart failure, and even death from cardiovascular disease.
People with highly variable bedtimes or sleep midpoints were at significantly higher risk – but only if they slept less than the median of seven hours and 56 minutes per night.
Those who slept longer than this did not show the same increased risk.
Researchers said irregular bedtimes can disrupt the body’s internal clock, which controls heart function, hormones, metabolism and the body’s ability to recover during sleep.
Going to bed at different times and sleeping less than eight hours could double heart attack risk
Wake-up time did not appear to affect risk, suggesting that going to bed at a consistent time is more important than the hour you wake up.
Other factors linked to higher risk included being male, having a higher body mass index and being unemployed.
Participants who experienced heart events also tended to have higher blood pressure, cholesterol and blood sugar levels compared with those who did not.
The study took other risk factors into account, including sex, BMI, employment, blood pressure, cholesterol, blood sugar and physical activity to make sure the results reflected the effect of sleep irregularity.
Earlier research shows that inconsistent sleep patterns and short sleep are linked to obesity, diabetes, and weaker immune function.
In the UK, adults get an average of six hours and 27 minutes of sleep per night, below the NHS-recommended seven to nine hours.
The study, published in BMC Cardiovascular Disorders, highlights that both sleep duration and regularity are important for long-term heart health.
Even if people cannot consistently get eight hours of sleep, keeping a regular bedtime may help reduce the risk of heart attack and other serious heart problems.
