It’s not only getting a decent night’s sleep that’s good for your health but also when you get it, new research suggests.
Those who do not keep to regular bed and wake-up times have a higher risk of stroke and heart attack, according to a study on UK adults.
Irregular sleep patterns increase the risk of conditions such as stroke, heart failure and heart attacks by more than a quarter, regardless of whether people are getting enough sleep overall.
Sleep disruptions can trigger inflammation which can lead to fatty build-up in the arteries as well as interruptions to circadian rhythm, which blood pressure and other cardiovascular functions are linked to.
Researchers examined data for 72,269 people aged 40 to 79 taking part in the UK Biobank study, with no history of major heart-related events such as a heart attack.
They wore an activity tracker for a week to record their sleep, with experts then calculating a Sleep Regularity Index (SRI) score for each person.
This score captured the day-to-day variability in bedtime, wake-up time, sleep duration and wake-ups during the night, with people given a score ranging from 0 (very irregular) to 100 (perfectly regular sleep-wake pattern).
Everyone in the study was grouped into either an irregular sleep group (SRI score less than 71.6), moderately irregular sleep group (SRI between 71.6 and 87.3), or regular sleep group (SRI score over 87.3).
Those who had irregular bedtimes had the highest risk of stroke, compared to those who slept for fewer hours overall but went to bed at the same time every night.
People were followed for eight years, during which time researchers analysed how many suffered conditions such as heart attack, stroke and heart failure.
Even after taking into account things that could influence the results such as coffee intake and exercise levels, irregular sleepers were 26 per cent more likely to suffer a stroke, heart failure or heart attack than those with regular sleep.
Moderately irregular sleepers were eight per cent more likely to do so, according to findings published online in the Journal of Epidemiology and Community Health.
Researchers also found that the SRI score was a continuous measure, with people’s risk of heart attack and stroke increasing the more irregular their sleeping patterns were.
Overall, the recommended amount of sleep for 18 to 64-year-olds is seven to nine hours per night, and is seven to eight hours for those aged 65 and over.
The study found that a greater proportion of regular sleepers (61 per cent) met the recommended sleep quota than irregular sleepers (48 per cent).
However, this made no difference to heart health for irregular sleepers, who had the same higher risk of stroke and heart attack even if they were getting enough sleep.
In contrast, moderately irregular sleepers saw their risks drop if they got adequate sleep.
Sleep deprivation can lead to obesity, memory loss, diabetes, heart disease, heightened and unstable emotions, impaired ability to learn and a reduced immune response, leaving you vulnerable to disease
The researchers, including from the University of Ottawa, said: ‘Our results suggest that sleep regularity may be more relevant than sufficient sleep duration in modulating major adverse cardiovascular event risk.’
Emily McGrath, senior cardiac nurse at the British Heart Foundation, said: ‘It is not clear exactly how sleep benefits the heart but research suggests that disturbed sleep is associated with higher levels of a protein called CRP.
‘This is a sign of inflammation, the process linked with heart and circulatory disease.
‘Sleep can also have an indirect impact on heart health, by affecting our lifestyle choices.
‘Studies have suggested that not sleeping enough might affect the hormones which influence our appetite, increasing our desire for sugary foods.
‘Over a long period of time this could lead to weight gain and a greater risk of coronary heart disease.
‘More research is needed to strengthen this discovery but the early results suggest there’s an important connection between sleep and heart and circulatory health.’