Working a week of night shifts every month does not increase the risk of heart disease, a study revealed on Tuesday.
Researchers at Aarhus University in Denmark found that there was no increased risk of coronary heart disease if you work up to seven night shifts per month.
The results contradict several previous studies which have established a link between heart disease and working nights.
Scientists analysed data on the working time registrations of more than 250,000 healthcare workers in Denmark from 2007 to 2015 alongside their hospital records.
Participants worked an average of 1.8 night shifts per month, and 93 per cent of them worked fewer than seven monthly night shifts.
PhD student Jesper Medom Vestergaard, who led the research, said: "In our study, we didn't see any association between the number of night shifts and the risk of coronary heart disease.
"Many international studies have otherwise suggested an association, which is why our results are interesting, not least because the previous studies are primarily based on questionnaires, whereas we've had an opportunity to compare specific data on working hours with people's health information."
But he added that the results did not negate the full health impact of night shifts, as very few of the participants worked nights permanently.
A study published by the European Heart Journal in 2021 found that people who work night shifts are at increased risk of developing an irregular and often abnormally fast heart rhythm called atrial fibrillation.
Shift work is known to have a significant impact on sleep duration and quality as it disrupts circadian rhythms - the body's internal clock.
The National Sleep Foundation recommends seven to eight hours of sleep a night for adults.
The number of night-time workers in the UK has fallen from 9.5 million in 2016 to 8.7 million in 2022, according to the Office for National Statistics.
