Neurologist Discusses Alzheimer's

Both, probably. Although we tend to think of Alzheimer's as a disease limited to the brain, it is likely that it also has metabolic and immune system effects that contribute to the general wasting, frailty and other signs we frequently see as dementia progresses. In addition, the disease causes problems that make the patient susceptible to other conditions. For example, difficulty swallowing leads to poor nutrition and greatly increases the risk of pneumonia. It is probably through both direct and indirect effects that Alzheimer's disease reduces life expectancy.