Body mass index and incidence of dementia

To study the relationship between body mass index (BMI) and risk of dementia, a cohort of 3,646 individuals aged > or =65 years living at home and without cognitive disorders at baseline were followed up for 8 years (the PAQUID [Personnes Agées Quid] Study). Subjects with a BMI < 21 had an increased risk of developing dementia as compared with subjects whose BMI was between 23 and 26 (odds ratio = 1.48, 95% CI = 1.08 to 2.04). However, when individuals who developed dementia early during the follow-up were excluded from the analysis, this relationship was no longer significant. A low BMI does not in itself seem to be a risk factor for dementia.