Shift Work Including Night Work and Long Working Hours in Industrial Plants Increases the Risk of Atherosclerosis

Abstract

There is an abundance of literature reporting an association between shift work and cardiovascular disease (CVD). Few studies have examined early manifestation of CVD using advanced modern methodology. We established a group of 65 shift workers and 29 day workers (controls) in two industrial plants. For the shift workers, the shift schedule includes rotating shifts with day, evening and nightshifts, some day and nightshifts lasting for 12 h. The current paper describes cross-sectional data in a study running for three years. We collected background data by questionnaire and measured blood pressure, heart rate, lipids, glycosylated hemoglobin (HbA1c) and C-reactive protein (CRP). We examined arterial stiffness (central blood pressure, augmentation pressure and index, and pulse wave velocity) by the use of SphygmoCor^® (AtCor Medical Pty Ltd, Sydney, Australia) and the carotid arteries by ultrasound. We assessed VO_2max by bicycle ergometry. We applied linear and logistic regression to evaluate associations between total number of years in shift work and cardiovascular outcome measures. The day workers were older and had more pronounced arterial stiffness compared to the shift workers. Number of years as a shift worker was associated with increased carotid intima media thickness (max IMT) (B = 0.015, p = 0.009) and an elevated CRP (B = 0.06, p = 0.03). Within the normal range for this age group, VO_2max was 41 (9) ml/kg/min. Rotating shift work including day and night shifts lasting up to 12 h and evening shifts are associated with CVD-risk factors. This could imply an increased risk for coronary heart disease and stroke among these workers. Therefore, preventive measures should be considered for these groups of workers in order to prevent such diseases.

Keywords: cardiovascular; occupational health; shift work.