Late-life adiposity is associated with lower dementia risk

Mid- and late-life obesity and dementia risk
While obesity in midlife increases the risk of dementia, late-life adiposity seems to be related to a decreased risk. However, the mechanisms underlying the inverse association in late life are poorly understood. This project aimed to further examine this by investigating the role of inflammation and lipid metabolism in the obesity and dementia risk association in mid- versus late life.

Three NEAR population studies: The Swedish Adoption/Twin Study of Aging (SATSA), Ageing in Women and Men: A Longitudinal Study of Gender Differences in Health Behavior and Health among Elderly (GENDER), and Origin of Variances in the Oldest-Old: Octogenarian Twins (OCTO-Twin), as well as the TwinGene study, were used to explore this.

Photo by i yunmai on Unsplash (scale)

Late-life adiposity is associated with lower dementia risk
In individuals aged 40-64 years (n=5999), a higher waist-hip ratio (WHR) was related to a 25% higher dementia risk. Inflammation (measured as C reactive protein) or lipid levels did not mediate this association. In persons aged 65 years and over (n= 7527), a higher Body Mass Index (BMI) but not WHR, was associated with 8% lower dementia risk. The association was partly mediated by higher CRP and lipoprotein levels. In conclusion, the negative effects of midlife adiposity on dementia risk were driven directly by factors associated with body fat distribution, with no evidence of mediation through inflammation or lipid levels. There was an inverse association between late-life adiposity and dementia risk, especially when the body’s inflammatory response and lipid homeostasis are intact.

Ida Karlsson, first author of the study. Photo: Gunilla Sonnebring

Publication
Karlsson IK, Zhan Y, Wang Y, Li X, Jylhava J, Hagg S, Dahl Aslan AK, Gatz M, Pedersen NL, Reynolds CA. Adiposity and the risk of dementia: mediating effects from inflammation and lipid levels. Eur J Epidemiol. 2022; 37(12): 1261-1271. https://doi.org/10.1007/s10654-022-00918-w