Loss of interest in activities with other people is often an early sign Sign
In medicine a sign is what a physician finds by examining a patient. For example, a patient with the symptom of pain might have signs of a fast heart rate, a pale face, a clammy touch and tenderness. of dementia. Other things can cause it too - depression Depression
A disorder where a person experiences a constant state of sadness and low mood which interferes with their daily activity. being a classic example. In people who turn out to have Alzheimer's though, we often recognize a typical pattern, which is that the initiative to do the activity is lost before the ability to perform the activity is lost. A classic example of this is the patient who has stopped singing, or playing a musical instrument, but who does so even a few weeks after starting treatment.

The way that the leisure activities are performed is also often a clue to dementia, and to the effects of treatment. Someone who likes to carry out complex activities (i.e., woodworking or cooking) now often needs someone else to be with them if they are to stay organized. Even at that, their performance might not be to the same standard.

Some leisure activities - such as working with sharp instruments, including tools or household appliances - will gradually require not just participation with someone else, but supervision by that person if they are to be performed safely. This can be awkward for all concerned - where children help their parents, it is often a complete reversal of how things used to be. I remember a man who had particular difficulty in accepting that his son now had to help him tie flies for fly-fishing, and what might have been a source of enjoyment for them both instead was a problem that they could never resolve. More commonly though, in my experience, people are glad for the help, so that these times together can be very precious.