Neurology Central

Body Mass Index and dementia, a conundrum


The occurrence of overweight, obesity and Alzheimer’s disease (AD) are increasing in both developed and developing countries. The first study to report a risk association between AD and being more overweight or obese, measured via higher body mass index (BMI; kg/m2), was published in 2003 [1]. Since then the epidemiological literature on BMI and dementia has escalated and is somewhat mixed [2]. Before discussing the epidemiology however, one needs to understand both exposure and outcome.

Exposure, Body Mass Index (BMI)

A common and generally acceptable measure for underweight, overweight and obesity in the general population is body mass index (BMI), calculated by dividing an individual’s body weight in kilograms (kg) by the square of the height in meters (m2). In 2013, obesity was recognized as a noncommunicable disease by the American Medical Association and it has been increasing to pandemic proportions in both developed and developing countries. By 2030 the prevalence of obesity (BMI > 30 kg/m2) in the U.S. is predicted to be approximately 42% [3], with a global estimate of 1.12 billion obese individuals, accounting for 20% of the world’s population [4].

Definition of the Outcome, Alzheimer’s Disease and Dementia

AD is the most common clinically diagnosed form of dementia. It is predicted that the number of people living with AD will almost double every 20 years to 115.4 million in 2050, with the largest increase occurring in low and middle income countries [5]. However, this may not be true in all areas of the world and there are conflicting data on trends in dementia incidence [6].

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