Physical activity, weight status, diabetes and dementia: a 34-year follow-up of the population study of women in Gothenburg.

Background: There is evidence of a synergistic interaction between obesity and sedentary lifestyle with respect to diabetes. Although diabetes is a known risk factor for dementia, it is unclear if both diseases have common aetiologies.
Methods: A community-based sample of 1,448 Swedish women, aged 38-60 years and free of diabetes and dementia in 1968, was followed by means of up to 5 examinations spread over 34 years. 9.6% of all women developed diabetes and 11.4% developed dementia (over 40,000 person-years of follow-up for each disease). Cox proportional hazard regression was used to assess the influence of selected risk factors on both diseases, and the relation between diabetes and dementia.
Results: Comparing risk factors for incident diabetes and dementia, both diseases showed a synergistic association with obesity combined with a low level of leisure time physical activity [hazard ratio (HR) for interaction = 2.7, 95% confidence interval (CI) = 1.2-6.3 for diabetes and HR = 3.3, 95% CI = 1.1-9.9 for dementia]. Development of diabetes doubled the risk for subsequent dementia (HR = 2.2, 95% CI = 1.1-4.4), which was slightly reduced upon adjustment for common risk factors.
Conclusions: Shared risk factors suggest a similar aetiology for diabetes and dementia and partially explain the association between diseases.
(© 2014 S. Karger AG, Basel.)