Night shift work characteristics and risk of incident coronary heart disease among health care workers: national cohort study

Sep 23, 2023International journal of epidemiology

How night shift work features relate to new heart disease risk in health care workers

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Abstract

Among 100,149 night workers, the incidence of coronary heart disease was 1.06 for women and 1.22 for men compared to day workers.

Night workers experienced a higher incidence of coronary heart disease compared to day workers, with specific ratios of 1.06 for women and 1.22 for men.
The average number of night shifts worked per month was 1.7 for women and 1.8 for men, with an average duration of less than 4 years.
No consistent links were found between various night work characteristics (such as the number of monthly night shifts or cumulative night shifts) and coronary heart disease risk.
Higher risks were noted in top exposure categories for certain night work characteristics, though the overall findings did not support a clear exposure-response relationship.

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BACKGROUND: Night work has been associated with coronary heart disease. The present study examined exposure-response relations between quantitative night work characteristics and coronary heart disease (angina pectoris or myocardial infarction) with the aim to contribute to evidence-based recommendations for low-risk night work schedules.

METHODS: We followed 100 149 night workers (80% women) and 153 882 day workers (78% women), all health care workers in Denmark with day by day payroll information on night shifts from 2007 to 2015. We analysed data with Poisson regression stratified by sex and adjusted for age, calendar year, diabetes, family history of cardiovascular disease, educational level, occupation, indicators for obesity, hypercholesterolaemia, and hypertension.

RESULTS: Female and male night workers worked on average 1.7 and 1.8 night shifts per month for an average duration of less than 4 years. During follow-up, 1198 night and 2128 day workers were hospitalized with first-time coronary heart disease. When compared with day workers, the overall incidence rate ratios for female and male night workers were 1.06 [95% confidence interval (CI): 0.97, 1.17] and 1.22 (95% CI 1.07, 1.39). Highest risks were observed in top exposure categories for several night work characteristics. However, no consistent exposure-response relations by number of monthly night shifts, cumulative night shifts, years with rotating night shifts, years with any night shift and consecutive night shifts were observed among the night workers of either sex.

CONCLUSIONS: This study of a population with low exposure to night work does not indicate that reducing extent of monthly night shifts, cumulative night shifts, years with rotating night shifts, years with any night shift and consecutive night shifts would reduce the risk of coronary heart disease.

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Night shift work characteristics and risk of incident coronary heart disease among health care workers: national cohort study

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