Incident dementia in women is preceded by weight loss by at least a decade.

BACKGROUND: Although several studies reported weight loss preceding the onset of dementia, other studies suggested that obesity in midlife or even later in life may be a risk factor for dementia.
METHODS: The authors used the records-linkage system of the Rochester Epidemiology Project to ascertain incident cases of dementia in Rochester, MN, for the 5-year period 1990 to 1994. The authors defined dementia using the criteria of the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV). Each case was individually matched by age (+/-1 year) and sex to a person drawn randomly from the same population, and free from dementia in the index year (year of onset of dementia in the matched case). Weights were abstracted from the medical records in the system.
RESULTS: There were no differences in weight between cases and controls 21 to 30 years prior to the onset of dementia. However, women with dementia had lower weight than controls starting at 11 to 20 years prior to the index year, and the difference increased over time through the index year. We found a trend of increasing risk of dementia with decreasing weight in women both at the index year (test for linear trend; p < 0.001) and 9 to 10 years before the index year (test for linear trend; p = 0.001).
CONCLUSIONS: Even accounting for delays in diagnosis, weight loss precedes the diagnosis of dementia in women but not in men by several years. This loss may relate to predementia apathy, loss of initiative, and reduced olfactory function.