Aims/hypothesis: We investigated associations between abnormal glucose regulation and family history of diabetes, separately and in combination with lifestyle risk factors.
Subjects and methods: This cross-sectional study comprised 3,128 men and 4,821 women, aged 35-56 years, half with a family history of diabetes. Oral glucose tolerance testing identified subjects with previously undiagnosed prediabetes (IFG, IGT) and type 2 diabetes. Information on lifestyle factors was obtained by questionnaire. Biological interaction was measured with the synergy index.
Results: A family history of diabetes conferred a higher odds ratio (OR) for type 2 diabetes in men (OR=3.1, 95% CI 1.7-5.6) than in women (OR=1.7, 95% CI 1.0-3.0), and the synergy index was 2.8 (95% CI 0.9-9.0), suggesting interaction between a family history of diabetes and sex. For prediabetes and diabetes combined, the synergy index was 1.7 (1.0-2.8). Exposure to only one lifestyle risk factor (obesity, physical inactivity, smoking or low sense of coherence [a psychosocial index]) increased the risk to a similar extent in men and women. Combined exposure to a family history of diabetes and lifestyle-related risk factors had a greater effect on type 2 diabetes than any of these factors alone, especially in men. However, analysis of interaction between a family history of diabetes and the lifestyle factors did not indicate any interaction for diabetes, but did indicate interaction for a family history of diabetes and obesity in women with prediabetes.
Conclusions/interpretation: Our data suggest a more pronounced effect of a family history of diabetes on the risk of type 2 diabetes in men than in women. While both a family history of diabetes and lifestyle risk factors had effects on type 2 diabetes, irrespective of sex, these effects did not appear to interact.