Hassing, L. B. et al. Overweight in midlife and risk of dementia: a 40-year follow-up study. Int. J. Obes. (Lond.) 33, 893–898 (2009).

Being overweight in midlife increases the risk of dementia in old age, according to the results of a study published in the International Journal of Obesity. This observation builds on previous investigations by the same researchers into the contributory effect of type 2 diabetes mellitus on the risk of dementia and reduced cognitive function.

Linda Hassing and co-workers analyzed data collected by the Swedish Twin Registry, which was initiated in the late 1950s. BMI was calculated for 1,152 participants who were aged 45–65 years in 1963; these measurements were used to predict incident dementia 40 years later.

Regression analyses indicated that men and women who were overweight in midlife (BMI ≥26.5 kg/m2) had an elevated risk of dementia, Alzheimer disease and vascular dementia. The correlation between BMI and vascular dementia was not statistically significant after controlling for the influence of diabetes mellitus and vascular diseases. By contrast, being overweight in midlife was still a statistically significant risk factor for Alzheimer disease even after controlling for diabetes mellitus and vascular disease. The same patterns were observed in both men and women, and so contradict the findings of previous studies that found an enhanced risk of dementia in women.

Hassing's team plan to investigate whether overweight affects cognitive performance among individuals not clinically diagnosed as having dementia. “Our analyses indicate that midlife overweight is also related to reduced cognitive function among elderly individuals without dementia,” she says.