Introduction Increasing years of recent rotating night shift work has been associated with increasing risk of coronary heart disease among nurses.

Objective We examined the association between numbers of monthly night shifts, other quantitative night work characteristics and coronary heart disease among nurses, physicians and other health care workers with the aim to provide evidence based recommendations for night work schedules.

Methods In a register-based national cohort study with a 2007–2015 follow-up, we followed 100,593 night workers (80% women) and 158,084 day workers (78% women) employed at public hospitals in Denmark. We defined a night shift (≥3 hours between 12am and 5am) and different quantitative night work characteristics (i.e., number of monthly night shifts, cumulative night shifts, years with rotating night shifts, years with any night shift and consecutive night shifts) from day by day payroll information on work hours from the Danish Working Hour Database. Outcome was first time hospital admission for coronary heart disease. At end of follow-up a subgroup of 34,432 participants reported lifestyle factors i.e. tobacco smoking, alcohol consumption, body mass index and prior regular night work.

Results During follow-up, 1203 night workers (68% women) and 2219 day workers (66% women) were diagnosed with coronary heart disease. Among night workers, we observed no consistent exposure-response relations for any quantitative night work characteristic. However, men, but not women night workers showed an overall increased incidence rate ratio of coronary heart disease of 1.22 (95% confidence interval 1.07–1.39) compared with dayworkers that could not be explained by medical or lifestyle factors.

Conclusion Our observation of no exposure-response relation between several quantitative night work characteristics and coronary heart disease does not provide support for an association between night work and coronary heart disease warranting specific night work schedules to prevent coronary heart disease.