Impact of Reduced Working Hours and Night Work Hours on Metabolic Syndrome: A Quasi-Experimental Study

OBJECTIVES: Epidemiological evidence linking long working hours and shift work to metabolic syndrome remains inadequate. We sought to evaluate the impact of reducing working hours on metabolic syndrome. METHODS: We compared the prevalence of metabolic syndrome among male manual workers in a manufacturing company (N = 371) before and after the introduction of policy to reduce daily work hours from 10 to 8 hours. Components of metabolic syndrome were measured in periodic health examinations before the intervention, 6–9 months after, and 1.5–2 years after the intervention. Generalized estimating equation models were used to estimate changes in the prevalence of metabolic syndrome. Analyses were stratified by day work versus shift work. RESULTS: The results showed a significantly decreased prevalence of metabolic syndrome 6–9 months following the intervention in day workers (risk ratio = 0.68, 95% confidence interval 0.52–0.88), but the benefit disappeared after 1.5–2 years. Shift workers showed a decreased prevalence of metabolic syndrome for the whole follow-up duration after the intervention, although the change was not statistically significant. CONCLUSION: Reducing working hours was associated with short-term improvement in metabolic syndrome in male manual workers.