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Diabetes and the Risk of Dementia

Diabetes increases the risk of Alzheimer’s disease and vascular dementia and the risk is stronger when diabetes occurs at mid-life than in late life according to university researchers in Sweden….

Researchers aimed to verify the association between diabetes and the risk of dementia, Alzheimer’s disease, and vascular dementia in twins and to explore whether genetic and early-life environmental factors could contribute to this association.

This study included 13,693 twin individuals aged ≥ 65 years. Dementia was diagnosed according to DSM-IV (Diagnostic Manual of Mental Disorders, 4th ed.) criteria. Information on diabetes was collected from the inpatient registry and self- or informant-reported history of diabetes. Data were analyzed following two strategies: 1) unmatched case-control analysis for all participants using generalized estimating equation (GEE) models and 2) cotwin matched case-control analysis for dementia-discordant twin pairs using conditional logistic regression.

Of all participants, 467 were diagnosed with dementia, including 292 with Alzheimer’s disease and 105 with vascular dementia, and an additional 170 were diagnosed with questionable dementia. Diabetes was present in 1,396 subjects. In GEE models, diabetes was associated with adjusted odds ratios (ORs) (95% CI) of 1.89 (1.51-2.38) for dementia, 1.69 (1.16-2.36) for Alzheimer’s disease, and 2.17 (1.36-3.47) for vascular dementia. Compared with late-life diabetes (onset age ≥ 65 years), the risk effect of mid-life diabetes (onset age < 65 years) on dementia was stronger. Conditional logistic analysis of 210 dementia-discordant twin pairs led to ORs of 2.41 (1.05-5.51) and 0.68 (0.30-1.53) for dementia related to mid- and late-life diabetes, respectively.

The results show that diabetes increases the risk of Alzheimer’s disease and vascular dementia in the Swedish twins. The risk effect is stronger when diabetes occurs at mid-life than in late life. These findings add to the growing evidence of a link between diabetes, vascular damage, and neurodegenerative changes in the brain. Genetic and early-life environmental factors might contribute to the association between late-life diabetes and dementia, but adulthood environments might be responsible for mid-life diabetes-dementia association. These findings suggest that diabetes-dementia association may develop across a lifespan. Further studies are required to reveal which early life and adulthood environmental factors as well as genes might be involved for the diabetes-dementia association.

In contrast to late-life diabetes, mid-life diabetes was associated with an increased risk of dementia even when controlling for genetic and familial factors, suggesting that mid-life diabetes-dementia association might be exogenous and is more likely attributable to adulthood environments (e.g., occupation and lifestyle such as exercise, diet, smoking, and social activities as well as glycemic control in patients with diabetes). The results indicate that genetic and unmeasured early-life environmental factors are likely to play a role in the association of late-life diabetes with dementia but could not explain mid-life diabetes in association with dementia, which implicated the involvement of adulthood environments in the development of mid-life diabetes-dementia association and highlighted the need to maintain a healthy lifestyle during adulthood in order to reduce the risk of dementia late in life.

Diabetes, Feb 2010