EDITOR—The paper by Whitmer et al supports the findings of an earlier study in showing that obesity in middle age predicts dementia in older age.1 2 The major apparent weakness of the study is the loss of 13 014 patients to follow-up. Their adiposity and sociodemographic characteristics at study entry (1964-73: n = 25 290) were reported to be the same as those who were followed up to 1994-2003. That is important. Their medical and physical characteristics are …