Poor glycemic control in workers with diabetes mellitus in relation to long working hours: a cross-sectional study.

We aimed to investigate the association between working hours and poor glycemic control using a cross-sectional data from the Korea National Health and Nutrition Examination Survey (KNHANES). The participants who were medically diagnosed with diabetes mellitus by a physician were defined as diabetic patients, and patients with hemoglobin A1c (HbA1c) levels >9.0% were considered as "poorly controlled". The association of HbA1c level with working hours was examined by linear regression plot, using local regression line and logistic regression analyses. The local regression plot showed a smooth increasing pattern: the longer were the working hours, the higher were the HbA1c levels, even though it was not statistically significant. Odds ratios of working hours over 52 h per week were higher with the criterion of poor diabetic control (HbA1c >9.0%). The results were significant in elderly female workers (odds ratio 3.30, 95% confidence interval 1.19-9.18). Long working hours were associated with poor glycemic control, specifically among elderly female workers with diabetes.