In my experience with working with many elderly patients, a lot of them are self-conscious of having "old person smell" so attempt to mask that with perfume/cologne. It's also harder for them to bathe and reach all the nooks and crannies so sometimes hygiene deteriorates.
One of the strongest smells in a nursing home isn't unchanged diapers it is that staph infection festering under a neglected old lady's underbreast area. Very infrequently checked due to modesty issues and caregivers trying not to offend and respect her decency but it does have to be monitored and checked routinely because that skin area stays moist and chafes against the folds and I've seen too many elderly women in severe pain from their bra straps chaffing the skin off here and getting infected.
Men of hackernews, check your elderly mothers underbreast area and make sure her caregivers are routinely keeping it clean and dry!!
This comment brought to you by a very sweet, very neglected old lady who we took out of a pretty bad situation in a care home and I will never forget that smell and the shame and plea for help in her eyes as I assessed what exactly was the source of her various ailments. And she was nonverbal so couldn't complain nobody was doing their damn jobs.