What factors explain the much higher diabetes prevalence in Russia compared with Norway? Major sex differences in the contribution of adiposity.

INTRODUCTION: Compared with many other countries Russia has a high prevalence of diabetes in men and women. However, contrary to what is found in most other populations, the risk is greater among women than men. The reasons for this are unclear. RESEARCH DESIGN AND METHODS: Prevalence and risk factors for diabetes at ages 40-69 years were compared in two population-based studies: Know Your Heart (KYH) (Russia, 2015-2018, n=4121) and the seventh wave of the Tromsø Study (Tromsø 7) (Norway, 2015-2016, n=17 649). Diabetes was defined by the level of glycated hemoglobin and/or self-reported diabetes and/or diabetes medication use. Marginal structural models were used to estimate the role of key risk factors for diabetes in differences between the studies. RESULTS: Age-standardized prevalence of diabetes was higher in KYH compared with Tromsø 7 in men (11.6% vs 6.2%) and in women (13.2% vs 4.3%). Age-adjusted ORs for diabetes in KYH compared with Tromsø 7 were 2.01 (95% CI 1.68 to 2.40) for men and 3.66 (95% CI 3.13 to 4.26) for women. Adiposity (body mass index and waist circumference) explained none of this effect for men but explained 46.0% (39.6, 53.8) for women. Addition of smoking and C reactive protein, as further mediators, slightly increased the percentage explained of the difference between studies to 55.5% (46.5, 66.0) for women but only to 9.9% (-0.6, 20.8) for men. CONCLUSIONS: Adiposity is a key modifiable risk factor that appears to explain half of the almost threefold higher female prevalence of diabetes in Russia compared with Norway, but none of the twofold male difference.