Type 2 diabetes among farmers and rural and urban referents: cumulative incidence over 20 years and risk factors in a prospective cohort study.

Abstract

Few studies have examined the risk of type 2 diabetes in various occupational groups. Farmers in Sweden have a low risk of coronary heart disease, but less is known about diabetes. To analyze the cumulative incidence and relative risk of type 2 diabetes among farmers and referents taking lifestyle factors and components of the metabolic syndrome into account. In a longitudinal observational cohort study we followed 1,220 farmers, 1,130 rural non-farmer referents and 1,219 urban referents over 20 years. Outcomes were generated from national registers and from two surveys 12 years apart. Baseline data were assessed at the first survey conducted in 1990-91. Farmers had a significantly lower risk of all diabetes compared with urban and rural referents (p<0.05). A total of 91 farmers (8.4%) and 102 non-farming rural referents (11.5%) were identified with type 2 diabetes over the 20 year study period (OR=0.70; 95% CI 0.52-0.95). Fractional analyses of lifestyle factors and components of the metabolic syndrome showed that the low risk of type 2 diabetes among farmers was explained in terms of physical activity and meal quality. Farmers had significantly higher physical capacity (p<0.001) and scored higher in a meal quality index than rural referents (p<0.001). The prevalence of type 2 diabetes was significantly lower among farmers. The low relative risk was explained by high physical activity and better meal quality, indicating that farmers' lifestyles and their work environment are health-promoting.