Abstract
BackgroundSeveral risk factors contribute to dementia, but the role of obesity remains unclear. This study investigated whether increased body weight or central obesity were associated with a higher risk of developing dementia in a representative sample of older English adults.MethodsWe studied 6582 participants from the English Longitudinal Study of Ageing (ELSA) who were aged ≥50 years and were dementia-free at baseline, that being either wave 1 (2002–2003) for study members who started at wave 1, or at either wave 2 (2004–2005) or 4 (2008–2009) for those who began the study as refreshment samples. Body mass index (BMI) was measured at baseline and categorized into normal weight (18.5–24.9 kg/m2), overweight (25–29.9 kg/m2) and obese (≥30 kg/m2). Central obesity was defined as a waist circumference (WC) >88 cm for women and >102 cm for men. Cumulative incidence of dementia was ascertained based on physician-diagnosed dementia, an overall score >3.38 on the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) and Hospital Episodes Statistics (HES) data at every ELSA wave from baseline until wave 8 (2016–2017). Cox proportional hazards models were used to assess the association between baseline BMI levels or abdominal obesity in relation to dementia incidence during the mean follow-up period of 11 years.ResultsFrom the overall sample, 6.9% (n = 453) of participants developed dementia during the follow-up period of maximum 15 years (2002–2017). Compared with participants with normal weight, those who were obese at baseline had an elevated risk of dementia incidence [hazard ratio (HR) = 1.34, 95% confidence interval (CI) 1.07–1.61] independent of sex, baseline age, apolipoprotein E-ε4 (APOE-ε4), education, physical activity, smoking and marital status. The relationship was slightly accentuated after additionally controlling for hypertension and diabetes (HR = 1.31, 95% CI 1.03–1.59). Women with central obesity had a 39% greater risk of dementia compared with non-central obese women (HR = 1.39, 95% CI 1.12–1.66). When compared with a normal BMI and WC group, the obese and high WC group had 28% (HR = 1.28, 95% CI 1.03–1.53) higher risk of dementia.ConclusionsOur results suggest that having an increased body weight or abdominal obesity are associated with increased dementia incidence. These findings have significant implications for dementia prevention and overall public health.
Highlights
Dementia is a substantial public health burden[1,2] and has become one of the leading causes of mortality in England, accounting for more than one in eight of all deaths (12.7%) in 2017.3 the identification of the modifiable risk factors for dementia onset has become a public health priority.[4]
Some studies suggest that waist circumference (WC), an indicator of abdominal obesity, might be a more sensitive adiposity marker than Body mass index (BMI),[27] and provided evidence to support the link between high adiposity and a greater dementia risk,[13,28] with a stronger relationship among older adults with larger WC.[29]
For the BMI analysis, the sample was comprised of 6582 participants (62.6 6 9.0 years; 46.0% men), whereas for the WC analyses, the sample was comprised of 5538 participants (63.5 6 9.3 years; 45.4% men) who were free from dementia at their baseline assessment and had complete cases on all variables of interest
Summary
Dementia is a substantial public health burden[1,2] and has become one of the leading causes of mortality in England, accounting for more than one in eight of all deaths (12.7%) in 2017.3 the identification of the modifiable risk factors for dementia onset has become a public health priority.[4]. There are claims that obesity may be protective and associated with higher survival in elderly individuals, representing evidence for reverse causality, known as the ‘obesity paradox’,26 which further compounds our current understanding of the relationship between obesity and dementia risk in older adults. Some studies suggest that waist circumference (WC), an indicator of abdominal obesity, might be a more sensitive adiposity marker than BMI,[27] and provided evidence to support the link between high adiposity and a greater dementia risk,[13,28] with a stronger relationship among older adults with larger WC.[29] two longitudinal studies found no association between late-life WC and dementia risk.[12,30]. This study investigated whether increased body weight or central obesity were associated with a higher risk of developing dementia in a representative sample of older English adults. Women with central obesity had a 39% greater risk of dementia compared with non-central obese women
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