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.