Influence of Shift Work on Coronary High Risk Status among Natural Gas Field Workers

Abstract

Background: The association between shift work and coronary high risk status (CHRS) is still unclear. The present work was designed to study the influence of shift work in a gas field petroleum company in Dakahlia on CHRS; as well as, to investigate its possible mechanisms. Methods: A cross-sectional approach was used and a systematic random technique was applied to select 200 shift workers and 200 non-shift workers. Both study groups were subjected to interview questionnaire about personal, social, smoking, occupational and medical histories. Clinical examination, including general and cardiovascular examinations, was done. Height, weight and waist circumference were measured and body mass index (BMI Kg/m 2) was calculated. Laboratory investigations included measurements of fasting blood glucose, lipid profile and uric acid; as well as, electrocardiographic examination (ECG). Coexistence of more than 2 conventional risk factors or diabetes mellitus (DM) or new and old coronary artery disease (CAD) defined CHRS. Vanillyl mandelic acid (VMA) was measured in 24 hours urine samples as a stress indicator for a randomly selected sub-sample from those with CHRS (25 shift and 25 non-shift workers). The R-R deep breathing variability test on the resting ECG as a measure for autonomic function was done for the same group. Results: The study revealed that 42.5% of shift workers were complaining of deterioration in performance and concentration during work. In addition, 35.5% of shift workers had the desire to change shift work. Among shift workers, 36% were smokers in comparison to 26.5% of non-shift workers with a statistically significant difference (p = 0.04). Rates of hypertension, hypercholesterolemia, high LDLcholesterol, low HDL-cholesterol, hypertriglyceridemia, obesity and DM showed a statistically significant increase among shift workers than non-shift workers (p < 0.05). The overall rate of CHRS was significantly higher among shift workers (p = 0.001). Multiple logistic regression analysis of coronary high risk status as the dependant variable revealed that shift work kept a significant effect on CHRS even after adjustment for other confounders (p= 0.002). Mean level of urinary VMA was significantly higher for shift workers than non-shift workers (p= 0.0001); meanwhile, significantly lower R-R variability indices were recorded among shift workers than non-shift workers (p < 0.05). Conclusion and Recommendations: The present study revealed that shift work has a significant impact on CHRS that might be related to sympathetic over-activity. It is recommended to screen for coronary risk factors in pre-placement and periodic medical examinations of shift workers with implementation of special preventive programs. Urinary VMA and R-R variability testing in ECG could be used as stress indicators among CHRS shift workers. Cases of CAD should be excluded from shift work.