They mean dementia.
Dementia (from Latin de- "apart, away" + mens (genitive mentis) "mind") is the progressive decline in cognitive function due to damage or disease in the brain beyond what might be expected from normal aging. Although dementia is far more common in the geriatric population, it may occur in any stage of adulthood. This age cutoff is defining, as similar sets of symptoms due to organic brain dysfunction are given different names in populations younger than adulthood.
Alzheimer's is a form of dementia.
Unfortunately, I do not know the answer to your question, but an educated guess would be a smaller cruiseline. Smaller typically also means more expensive. Why would this person cruise alone?