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.