Study of shift work and risk of coronary events

Background: The effects of shift work on coronary heart diseases (CHD) are well described. Most of the studies on coronary events in shift workers are supportive of the hypothesis that they are at increased risk. Objective: The objective of this study was to investigate the relation shift work has to risk of CHD in a cohort of men from different Asian races working in a fertilizer plant in the Middle East. Design: This is a case series of cohort study. Subjects: The medical records for 2562 staff employed at the plant, from the start of the company in 1972 till 2003, were surveyed. Of these, 648 were shift workers and 1914 were daytime workers. A total of 223 employees had cardiovascular event. Methods: For each case we recorded the date and age at start of employment, and the age at the time of diagnosis. Data from their last medical examination in the company were used to calculate their BMI, and to register whether they were smokers, had diabetes, or were senior or intermediate staff. Univariate and multivariate statistical analyses were performed. Results: The incidence of CHD is significantly higher in shift workers (13.5%) compared with the daytime workers (7.1%). Also, there was a statistically significant difference between shift workers and daytime workers concerning hypertension and cerebrovascular incidents. Conclusion: Our results suggest the possibility of an overall relationship between shift work and cardiovascular diseases.