Hey there.
I'm not sure if its related to the alzheimers illness or a seperate mediacal issue but my dad has VERY little appetite. He has certainly developed a sweet tooth, but eats very small ammounts. It got to a point that he dropped to about 9 stone (he is 5'11"). Fortunately he is putting some of the weight back on.
His GP prescribed some high calorie drinks (milkshakes I think- their name escapes me now, but I can find out)and they seem to help.
This all happened within the last 2 years since he was diagnosed so I'm not sure whether there is a similarity in terms of onset. However at 58 years old, he is of a similar age to your husband.
Tony