High BMI negatively associated with dementia in women, low BMI linked with disease in men

Being overweight was negatively associated with the incidence of dementia in women in Germany, while being underweight was linked to dementia in men, researchers reported in the Journal of Alzheimer’s Disease.

“The prevalence of dementia is likely to increase in the following decades because of aging of the population — and there is no cure for dementia yet,” Karel Kostev, PhD, study author and scientific principal for epidemiology research at IQVIA in Frankfurt, Germany, said in a related press release.

Kostev and colleagues conducted a retrospective cohort study of 296,767 patients (mean age, 70.2 years; 54.3% women) followed in one of 832 general practices in Germany from 2006 to 2019. Researchers analyzed associations between BMI and 10-year incidence of dementia in women and men, considering age, sex and comorbidities, and included Alzheimer’s disease, vascular dementia and undefined dementia in the diagnosis of dementia. BMI categories included underweight (<18.5 kg/m²), normal weight (18.5-24 kg/m²) overweight (25-29 kg/m²) and obese (30 kg/m² or more).

According to study results, 0.9% of patients were underweight, 25.5% normal weight, 41.5% overweight and 32.1% obese. The 10-year incidence of dementia significantly decreased with rising BMI, from 11.5% in women who were underweight to 9.1% in those who were obese, and from 12% in men who were underweight to 8.2% in those with obesity.

Overweight, compared with normal weight, in women was significantly and negatively associated with dementia (HR = 0.93; 95% CI, 0.88-0.97), while in men, the only BMI category significantly and positively associated with dementia was underweight (HR = 1.58; 95% CI, 1.11-2.25).

According to a related press release, obesity in women was significantly and negatively associated with AD (HR = 0.81; 95% CI, 0.7-0.93,) and overweight was negatively associated with undefined dementia (HR = 0.9; 95% CI, 0.85-0.96).

Similarly, there was a negative and significant association between obesity and AD in men (HR = 0.82; 95% CI, 0.69-0.98), while underweight was positively associated with undefined dementia (HR = 1.95; 95% CI, 1.3-2.93).

“It appears that there is a strong and positive relationship between underweight and dementia in older men,” study author Louis Jacob, MD, PhD, of the research and development unit at Parc Sanitari Sant Joan de Déu in Barcelona, said in the release. “In this context, cognitive impairments should be regularly assessed in older male patients with BMI less than 18.5 kg/m² ... On the other hand, overweight may protect against dementia in older women, suggesting that a moderate weight access in late life may be acceptable from a cognitive perspective.”

The authors acknowledge that, “more studies are needed to corroborate or invalidate these findings in other countries and settings.”

Reference:

Overweight was negatively associated with dementia in women, whereas there was a positive underweight-dementia relationship with men. https://www.eurekalert.org/news-releases/962553. Published Aug. 23, 2022. Accessed Aug. 23, 2022.