A new review and meta-analysis assessed the risk of cardiovascular disease (CVD) events associated with shift work and investigated whether there is a dose-response relationship[i].
It is estimated that 15-30 % of workers have rotating shift work patterns that include a mixture of day, afternoon and night shifts. Shift work is common in a range of industries such as healthcare, hospitality, emergency services and transportation. These work schedules alter the worker’s circadian rhythm, which may lead to adverse health effects. In addition, there is a higher prevalence of inactivity, smoking, excess weight and poor diet among shift workers than those who do not work shifts.
There were 21 studies included in the meta-analysis, with a total of 173,010 participants. Overall, the risk of any CVD event was 17 % higher among shift workers than day workers, and the risk of coronary heart disease (CHD) was 26 % higher among shift workers. The risk of mortality from either CVD or CHD was almost 20 % higher among shift workers.
The risk of developing any CVD seemed to increase after the first five years of shift work, with a 7.1 % increase in risk of CVD events for every additional 5 years of shift work. This is the first meta-analysis to show a dose-response relationship between exposure to shift work and CVD risk.
The reviewers did not comment on whether the increased risks of CVD are likely to be caused by the shift work itself, or by other factors such as smoking, poor diet and inactivity. They note that factors such as these are rarely considered in shift work research, and that it is important for future studies to take these into consideration. It is also pointed out that different studies use different definitions of ‘shift work’, and that the definition should include the duration of exposure, shift system and intensity. This would allow future studies to provide better understanding of whether CVD risk is associated with any specific shift work pattern.
[i] Torquati, L., Mielke, G. I., Brown, W. J. & Kolbe-Alexander, T. Shift work and the risk of cardiovascular disease. A systematic review and meta-analysis including dose–response relationship. Scandinavian Journal of Work, Environment & Health doi:10.5271/sjweh.3700 http://www.sjweh.fi/show_abstract.php?abstract_id=3700 (Accessed 29 December 2017)