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Longer Working Hours Associated with Higher Type 2 Incidence

 

Socioeconomic status plays a role in how strong the association is….
Previous studies have shown an association between working longer hours and risk factors that can contribute to type 2 diabetes incidence. These risk factors included physical inactivity, unhealthy lifestyle, poor nutritional choices, and cardiovascular disease. Other studies have found the association between increased risk for cardiovascular disease and working hours is more pronounced in those with lower socioeconomic occupations, such as jobs involving manual labor.
This study employed a socioeconomic status-stratified meta-analysis to determine if an association between working longer hours and type 2 diabetes would be stronger in those with lower socioeconomic status compared to their higher socioeconomic counterparts. The analysis included 23 total cohort studies with a total of 222,120 participants. The participants were stratified into either a low, intermediate or high socioeconomic status group. Z statistics were used to determine the association between longer hours and diabetes incidence with respect to socioeconomic status. Normal working hours were defined as 35-40 hours per week while longer working hours were more than 55 hours per week.
Results showed a risk ratio for type 2 diabetes incidence to be 1.07 for those working longer hours compared to normal working hours (95% CI 0.89-1.27, difference in incidence 3 cases per 10,000 person years). The association between longer working hours was found to be stronger in those with a lower socioeconomic status (risk ratio 1.29, 95%CI 1.06-1.57, difference in incidence 13 cases per 10,000 person years). The association was not apparent in the high socioeconomic status group (risk ratio 1.00, 95% CI 0.80-1.25, incidence difference 0 per 10,000 person years).
The results of this meta-analysis show an association between working extended hours and type 2 diabetes incidence. This association was most prominent when socioeconomic status was taken into account. An association was observed in those with a low socioeconomic status who were working greater than 55 hours per week. Due to the design of this study, only an association can be reported. A causal relationship cannot be determined as confounding cannot be ruled out. Also, the studies used in the analysis were not uniform in how a diabetes diagnosis was determined.
Practice Pearls:
  • Working longer hours has been shown to increase risk factors for type 2 diabetes
  • Working more than 55 hours per week and having a low socioeconomic status were associated with a higher type 2 diabetes incidence
  • Due to the design of this study, only an association can be reported. A causal relationship cannot be determined as confounding factors cannot be ruled out.

Kivimaki M, Virtanen M, Kawachi I, Nyberg ST et al Long working hours, socioeconomic status, and the risk of incident type 2 diabetes: a meta-analysis of published and unpublished data from 222 120 individuals. Lancet Diabetes Endocrinol 2014