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.