High midlife and late-life adiposity may increase risk for dementia. Late-life decrease in body mass index (BMI) or body weight within several years of a dementia diagnosis has also been reported. Differences in study designs and analyses may provide different pictures of this relationship. Thirty-two years of longitudinal body weight, BMI, waist circumference, and waist-to-hip ratio (WHR) data, from the Prospective Population Study of Women in Sweden, were related to dementia. A representative sample of 1,462 nondemented women was followed from 1968 at ages 38-60 years, and subsequently in 1974, 1980, 1992, and 2000, using neuropsychiatric, anthropometric, clinical, and other measurements. Cox proportional hazards regression models estimated incident dementia risk by baseline factors. Logistic regression models including measures at each examination were related to dementia among surviving participants 32 years later. While Cox models showed no association between baseline anthropometric factors and dementia risk, logistic models showed that a midlife WHR greater than 0.80 increased risk for dementia approximately twofold (odds ratio 2.22, 95% confidence interval 1.00-4.94, p = 0.049) among surviving participants. Evidence for reverse causality was observed for body weight, BMI, and waist circumference in years preceding dementia diagnosis. Among survivors to age 70, high midlife waist-to-hip ratio may increase odds of dementia. Traditional Cox models do not evidence this relationship. Changing anthropometric parameters in years preceding dementia onset indicate the dynamic nature of this seemingly simple relationship. There are midlife and late-life implications for dementia prevention, and analytical considerations related to identifying risk factors for dementia.

Introduction: High dietary intake of long chain, polyunsaturated fatty acids is associated with lower Alzheimer's disease (AD) risk.Methods: Washington Heights‐Hamilton Heights‐Inwood Columbia Aging Project is a multiethnic, prospective observational study of aging and dementia among elderly (≥ 65 years). Dietary intake was measured using a food frequency questionnaire. Dietary short‐, medium‐, and long‐chain fatty acid intakes were categorized by number of carbons and double bonds. Consensus AD diagnoses were made. Associations between AD risk and dietary fatty acid and cholesterol intakes were estimated using multivariable Cox proportional hazards regression models.Results: Of 2612 multiethnic women (67%) and men (baseline age 76.3 [6.4] years), 380 developed AD over an average 4.5 years follow‐up. Lower risk of AD was associated with increasing intakes of docosahexaenoic acid (DHA; hazard ratio [HR] = 0.73, 95% confidence interval [CI]: 0.57 to 0.95, P = 0.018) and eicosapentaenoic acid (EPA; HR = 0.74, 95% CI: 0.57 to 0.95, P = 0.021), and longer AD‐free survival (P < 0.05).Discussion: Higher intake of DHA and EPA are protective for AD.

Level of adiposity is linked to dementia in epidemiological studies. Overweight and obesity in mid- and late-life may increase risk for dementia, whereas decline in body weight or body mass index (BMI) and underweight in years preceding and at the time of a dementia diagnosis may also relate to dementia. Longitudinal studies with sufficient follow-up are necessary to estimate trajectories that allow better understanding of the relationship between adiposity indices and dementia over the life course. We evaluated the natural history of BMI in relationship to clinical dementia over 37 years in the Prospective Population Study of Women (PPSW) in Sweden. PPSW is a systematic sample of 1462 women born 1908, 1914, 1918, 1922, and 1930 and aged 38-60 years at baseline. Examinations occurred in 1968, 1974, 1980, 1992, 2000, and 2005. Statistical analyses were conducted using mixed effects regression models. Trajectories of BMI over 37 years as a function of age differed between women who did versus did not develop dementia. Women developing dementia evidenced a lesser increase in BMI from age 38 to 70 years. After age 70, the BMI slope decreased similarly (no "accelerated decline") irrespective of dementia status. A lower BMI before and during dementia onset was observed. Women with similar BMI at mid-life exhibited a different pattern of BMI change as they approached late-life that was related to dementia onset. BMI may be a potential marker of dementia-related neuropathologies in the brain. Dementia is related to a common risk factor, BMI, from mid-to late-life.

Level of adiposity is linked to manifest dementia and Alzheimer's disease in epidemiological studies. Overweight and obesity in mid- and late-life may increase risk for dementia, whereas decline in body weight or body mass index and underweight in years preceding and at the time of a dementia diagnosis may also relate to dementia. The role of adiposity during the period of cognitive decline is, as yet, not understood; however, some hypotheses relating adipose tissue to brain can be drawn. This review focuses on potential, varied mechanisms whereby adipose tissue may influence or interact with the brain and/or dementia risk during the dynamic period of life characterized by both body weight and cognitive decline. These mechanisms relate to: a) adipose tissue location and cell types, b) body composition, c) endocrine adipose, and d) the interplay among adipose, brain structure and function, and genes. This review will illustrate that adipose tissue is a quintessential, multifunctional tissue of the human body.