If you clock in for work in the early hours when most of the population is still asleep, you may have heard that it increases the risk of heart disease. But now there is good news from Aarhus University for those of us who work night shifts. A new study shows no increased risk of coronary heart disease if you work up to seven night shifts per month.
PhD Student Jesper Medom Vestergaard from the Department of Clinical Medicine is responsible for the study, which is based on working time registrations of more than 250,000 employees from 2007-2015, combined with their hospital records.
"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," says Jesper Medom Vestergaard.
In the study, Jesper Medom Vestergaard had access to day-to-day information on working hours for a total of 254,031 healthcare worers and other employees in the Danish regions, and this information was linked with their health information, including information from the Danish National Patient Register.
"Employees in the regions work on average 1.8 night shifts per month, and 93 per cent of them work fewer than seven monthly night shifts. The study shows that this is not associated with an increased risk of coronary heart disease."
Jesper Medom Vestergaard emphasises, however, that the results of the study do not mean that everyone working night shifts can breathe a sigh of relief.
"Most of the 250,000 paticipants in our study work in the healthcare sector, and few of them work nights permanently. Therefore, we can’t conclude that there is not an increased risk of coronary heart disease associated with night shifts. Many other factors may be in play, but the data in the analyses were adjusted for age, sex, family history of cardiovascular disease and other diseases associated with coronary heart disease."
Jesper Medom Vestergaard will follow up with a new study, in which he will look at the risk of breast cancer, which has also previously been linked to night work.
PhD Student Jesper Medom Vestergaard
Department of Clinical Medicine, Health, Aarhus University
E-mail: jespvest@clin.au.dk
Clinical Professor and Chair Henrik Kolstad
Occupational Medicine, Department of Clinical Medicine, Health, Aarhus University
Mail: kolstad@clin.au.dk
Mobile: +4529610359
International Journal of Epidemiology
Systematic review
People
Night shift work characteristics and risk of incident coronary heart disease among health care workers: national cohort study
23-Sep-2023
No conflict of interest