Body weight and cognitive impairment

Dementia has become a major public health concern due to population aging. Recent failures in clinical drug trials highlight the importance of evaluating and treating patients with dementia as early as possible.

Weight loss is common in people with dementia, particularly Alzheimer’s disease, and it is correlated with increased mortality. Epidemiological studies have shown that late-life weight loss can precede the cognitive decline and begins years before the diagnosis of dementia. Concomitantly late-life elevated body mass index (BMI) confers a lower risk of having dementia. Several factors directly related to neurodegeneration could lead to weight loss in dementia, including cognitive and psychiatric problems, altered olfaction and gustation, and pathology of important structures in the brain, particularly the hypothalamus.

The hormone leptin may partially explain the mechanism of how weight loss can precede the cognitive decline. There are differences in the association between midlife BMI and dementia compared to late-life BMI and dementia. Being overweight or obese in mid-life is a risk factor for dementia.

Previous studies were mainly based on BMI as a measurement of weight loss, which does not allow one to determine the direction of the association between weight loss and the dementing process. Body composition analysis should be included in further research.