Night shift work and myocardial infarction in the UK Biobank

Background Shift work has become popular along with adverse effects such as disrupted biological rhythms, metabolic changes, sleep disorders and myocardial infarction. Studies have shown a link between myocardial infarction and shift work, but evidence is still lacking. Aims We aim to explore the association between present and past shift work and risk of myocardial infarction in a large population of European workers. Methods We analysed data from the UK Biobank with >500 000 participants and an average 12-year follow-up duration. Cox proportional hazard models were employed to analyse the relationship between present shift work (n = 265 064), lifetime duration or frequency of shift work (n = 71 428) and the risk of myocardial infarction, as well as the association between rest day during shift work and myocardial infarction incidents in night shift workers (n = 14 588). Results Night shift workers had a higher risk of myocardial infarction compared to day workers, including ‘shift but never/rarely night shifts’ (hazard ratio [HR] = 1.09, 95% confidence interval [CI] 1.00–1.20), ‘some night shifts’ (HR = 1.13, 95% CI 1.01–1.27) and ‘usual/permanent night shifts’ (HR = 1.21, 95% CI 1.07–1.37), respectively. Similarly, higher frequency and longer duration of night shift work were associated with the increased risk of myocardial infarction (<10 years: HR = 1.20, 95% CI 1.01–1.42; ≥10 years: HR = 1.51, 95% CI 1.28–1.77; or an average of more than eight nights per month: HR = 1.45, 95% CI 1.23–1.71). However, longer rest days couldn’t decrease myocardial infarction risk compared to those who rest 1 day. Conclusions Present and lifetime exposure to night shifts were associated with a risk of myocardial infarction and did not benefit from longer rest days.