The most likely explanation is that there is something about these individuals or about this disease that affects body mass index (BMI) before the clinical syndrome becomes apparent -- that loss of BMI reflects the disease process itself.
There are actually very few predictors of Alzheimer's disease, ... This study makes us think about the spectrum of clinical signs of AD beyond changes in memory and behavior and motor skills. Changes in BMI are easy to measure in a doctor's office without an expensive scan.