The relationship between working schedule patterns and the markers of the metabolic syndrome: comparison of shift workers with day workers.

OBJECTIVES This study examined the effect of shift work on developing the metabolic syndrome by comparing groups of exposed and unexposed Iranian drivers. METHODS We considered as night-shift drivers those drivers whose shifts included at least 15 h per week between 9:00 p.m. and 7:00 a.m. Daytime drivers were defined as drivers working regularly without shift work. 3039 shift work drivers were selected. These were matched with non-shift workers. The differences in baseline characteristics and the prevalence of the components of the metabolic syndrome were assessed with Student's t test, and chi-square tests. RESULTS We found central adiposity in 52.0% of the shift workers versus 42.6% of the day workers (p < 0.0001). The hypertension component was not significantly related to shift work (p > 0.05); but there were significant differences as regards other components of the metabolic syndrome (p < 0.0001). Among the shift workers, the odds ratios of the increased FBS, low HDL-C, higher TG levels, as well as higher waist circumference were 1.992 (95% CI: 1.697-2.337), 1.973 (95% CI: 1.759-2.213), 1.692 (95% CI: 1.527-1.874), and 1.460 (95% CI: 1.320-1.616), respectively. The metabolic syndrome was more common among the shift workers (OR = 1.495; 95% CI: 1.349-1.657). CONCLUSION In evaluating such results, further consideration is needed to find pathophysiological clarification; in turn, stress linked to shift work must be considered to likely have had a relevant influence on the outcome. In our opinion, shift work acts as an occupational factor for the metabolic syndrome.