Data from: Body mass index, diet, physical inactivity and the incidence of dementia in one million UK women

Objective: To help determine whether mid-life obesity is a cause of dementia, and whether low BMI, low caloric intake and physical inactivity are causes or merely consequences of the gradual onset of dementia, we recorded these factors early in a large 20-year prospective study and related them to dementia detection rates separately during follow-up periods 0-4, 5-9, 10-14 and 15+ years. Methods: 1,136,846 UK women, mean age 56 (SD=5) years, were recruited in 1996-2001 and asked about height, weight, caloric intake and inactivity. They were followed until 2017 by electronic linkage to National Health Service records, detecting hospital admissions with mention of dementia. Cox regression yielded adjusted rate ratios (RRs) for first dementia detection during particular follow-up periods. Results: 15 years after the baseline survey only 1% were lost to follow-up and 89% remained alive with no detected dementia, of whom 18,695 had dementia detected later, at mean age 77 (SD=4) years. Dementia detection during years 15+ was associated with baseline obesity (BMI 30+ versus 20-24 kg/m2: RR=1.21, 95% CI 1.16-1.26; p