Examining if being overweight really confers protection against dementia: Sixty-four year follow-up of participants in the Glasgow University alumni cohort study

Abstract

BackgroundRecent large-scale studies suggest that obesity and overweight may confer protection against future dementia. This observation could, however, be generated by reverse causality. That is, weight loss in the incipient phase of dementia ascribed to diminished self-care, including sub-optimal nutrition, would have the effect of generating such an inverse association. One approach to circumventing this problem would be to measure weight in a population which is young enough to be free of the symptoms of dementia which is then followed up for dementia occurrence over many decades.MethodsIn a prospective cohort study, body mass index, and other potential risk factors, were measured in 9547 male university undergraduates (mean age 20.5 years) in 1948–68 who were then linked to national mortality registers.ResultsOf 2537 deaths over a mean of 50.6 years follow up, 140 were ascribed to dementia. There was no association between overweight and future dementia deaths (age-adjusted hazard ratio; 95 % confidence interval: 0.93; 0.49, 1.79).ConclusionIn this cohort study of former university students, being overweight in youth did not confer protection against later dementia death.

Body mass index and risk of dementia: Analysis of individual‐level data from 1.3 million individuals

“…Our findings are in agreement with the most recent systematic review and meta-analysis, published in 2016, which identified four cohort studies with BMI assessed in midlife and incident dementia ascertained at older ages by clinical examinations at follow-up [9] . Although this is not a universal observation [34] , [35] , the summary relative risk of dementia for obesity compared with normal weight in midlife was significantly elevated. In the Cardiovascular Health Study of 2800 US adults, an increased risk of dementia was found among those obese in midlife but was reversed for late-life BMI [5] , a finding replicated in the CAIDE study of 1300 Finnish adults [7] .…”

Respiratory Disease and Lower Pulmonary Function as Risk Factors for Dementia

“…Fifth, a recent observational study linked early life cardiorespiratory fitness with later young-onset dementia, 71 though a similar association was not observed between cardiovascular disease risk factors and late-onset dementia mortality elsewhere. 72 In the present context, these processes-the life course paradigm in dementia aetiology -are perhaps most relevant to pulmonary function rather than respiratory disease. There are at least three plausible mechanisms for the observed association between poorer pulmonary function and subsequent dementia: (i) pulmonary function may serve as a proxy for other exposures earlier in the life course which increase dementia risk; (ii) the association may result from the shared aetiology between pulmonary, cardiovascular disease and dementia; and (iii) hypoxic damage to the brain resulting from poorer pulmonary function, i.e.…”

Adiposity in middle and old age and risk of death from dementia: 40-year follow-up of 19,000 men in the Whitehall study

“…Study results include positive associations between increasing BMI and dementia [12], to a U-shaped relationship with both low and high BMI being associated with increased risk of dementia [21], and more complicated relationships where high BMI at mid-life appears to be a risk factor, while in old age it appears to be protective , [22,23]. A prospective cohort study of weight in university students who were followed-up for 50 years reported no association of overweight in early adult life with death from dementia [24]. One other study examined change in weight and its association with dementia, and reported a significant association, although it only looked at weight rather than BMI and weight and had an older cohort with a shorter follow up [25].…”