Obesity, a disease in itself, is a well known cause of other diseases. Midlife obesity, in particular, has been linked with an increased risk of late-life dementia and Alzheimer’s disease. Interestingly, patients who have dementia due to Alzheimer’s disease are actually more likely to be underweight.
The cause of this association has been unclear. It has been speculated that loss of body mass may be the result of dementia. This makes sense because dementia sufferers may simply be forgetting to eat. Or the inherent decrease in physical activity associated with dementia leads to loss of muscle mass. There is also the possibility that anti-Alzheimer’s medications has adverse effects on appetite.
However, according to a recent study published in Neurology, the authors were able to demonstrate a correlation between lower body mass index (BMI) and the presence of biomarkers suggestive of Alzheimer’s disease pathology on brain imaging and in cerebrospinal fluid. These patients had normal cognition or mild cognitive impairment (MCI). Lower BMI in these subjects cannot be explained as a consequence of dementia since they do not have the disease. This leads researchers to suggest that there may be systemic changes in appetite or metabolism as an early manifestation of the disease process.