Why do old people (especially women) smell odd?
I dont mean their "sense" of smell, I mean their body odor.  Even the
ones that take showers on a regular basis.

A large percentage of elderly people (more than 70%) do not produce
enough saliva, a condition called xerostomia. This condition is
considered to be part of the normal aging process, but it is also
caused by several commonly prescribed medications including
antidepressants, blood pressure medications, diuretics, and sedatives.
The less saliva secrete encourages the growth of a particular type of
bacteria which cause halitosis (Bad Breath). It's also not easy to
avoid halitosis if you have false teeth.
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Bodily odors are hard to separate from our daily living environment.
Typical odors released by the human body would include perspiration
(isovaleric acid) and scents unique to aging (nonenal, indole and
skatole). Bacteria decomposes perspiration and skin oils and causes
such odors to be released.
Nonenal aging odor is a unique smell that is emitted from the human
body when a person reaches a certain age. This odor occurs when the
fat of the sebum changes chemically.
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And one more ... declining taste and smell is a normal part of the
aging process for many people. Age-related impairment of the senses
can be caused by many factors.
So >>>> If you cannot smell, how do you know you smell badly ?

TO add to antontodorov-ga's comment, in my observation, older and
elderly folks don't pay as much attention to personal hygiene as they
once did. Bathing less frequently would cetainly be a factor.

Every person has body odor, to a greater or lesser degree, but what
actually causes it? A researcher at Shiseido Laboratories has traced
the problem to a fatty acid known as palmitoleic acid. He has also
learned that the body of a person up to about the age of 30 does not
secrete a noticeable amount of this substance, but that once a
person--whether male or female--hits 40, the volume rises sharply. The
volume of palmitoleic acid released by the human body is 10 times as
great among people in their seventies as in their forties.
http://web-japan.org/trends00/honbun/tj990921.html