Have read some, not all, the responses. Apologies if I repeat some of what already has been said.
The subject has interested me for years... The molecule responsible for the 'old people smell' is nonenal (nine carbon aldehyde, for those interested). Not sure how or why it is produced in older people, will have to read into that! Some alteration in our metabolism.
As has been mentioned above, washing regularly (I dry brush a few times a week too), washing clothes, bedding, airing the rooms even in winter. In the summer I wash duvets and air them in the sun whenever possible. All helps.
Our sense of smell varies from person to person, but it is the most direct of our senses, and it evokes strong, immediate responses and emotions. So for myself, as I am particularly sensitive to smells, I do my best not to have an 'iffy' one...