Policemen and firefighters have increased risk for type-2 diabetes mellitus probably due to their large body mass index: a follow-up study in Japanese men

BACKGROUND: Policemen/firefighters may have increased risk for mortality from ischemic heart disease and from all causes. We compare incidence of type-2 diabetes mellitus (DM), a well-known predictor for mortality, in policemen/firefighters with that in two other worker-groups. METHODS: A follow-up study of 5,130 healthy Japanese men aged 30-49 years at baseline consisted of three worker-groups; 3,111 clerical workers, 1,122 manual/production and transport/communication workers, and 897 policemen/firefighters. Incident DM was identified by "fasting serum glucose >or=7.00 mmol/L" or/and "under medical treatment for DM." Hazard ratio (HR) and 95% confidence interval (95% CI) for incident DM was estimated by Cox's proportional hazard models using clerical workers as a reference group (HR=1.00). Baseline age, body mass index (BMI, kg/m(2)), drinking, smoking, exercise, and education were computed as confounders. RESULTS: During mean follow-up periods of 8.4 years, 155 clerical workers, 51 manual/production and transport/communication workers, and 74 policemen/firefighters had incident DM (5.9, 5.7, and 9.6 per 1,000 person-years, respectively; P=0.001 by chi(2)-test). Policemen/firefighters had significantly increased risk for incident DM against clerical workers (age-adjusted HR (95% CI): 1.65 (1.25, 2.18)), but the significance disappeared after adjustments for BMI (age- and BMI-adjusted HR (95% CI): 1.16 (0.87, 1.54)). Manual/production and transport/communication workers had no increased risk. CONCLUSIONS: Policemen/firefighters have increased risk for DM probably due to their large BMI. Body weight control may be more efficient for prevention of DM and DM-related health problems in policemen/firefighters than in other workers.