A study from University College London of 48 dementia patients suggests that an increasingly warped sense of humor may be an early warning sign of impending frontotemporal dementia, which is one of the more rare forms of dementia and affects the area of the brain involved with personality and behavior. Looking back over nine years leading to the dementia diagnosis, family and friends felt the patients had developed a dark sense of humor, coupled with a tendency to prefer slapstick to satire.
Somewhat in contrast, a study at the University of Aberdeen of 116 people, 36 of whom were over 65, tended to show that the older people were equally skilled at interpreting normal conversations as the other participants, but that the over-65 group was somewhat less skilled at interpreting conversations involving sarcasm.
Links to articles about the dementia/humor study, and the study itself, have been posted in Diagnosis & Tests:
Altered Sense of Humor in Dementia
A link to an article about the study concerning age and sarcasm, as well as the study itself, have been posted in Aging:
Older adults have difficulty in decoding sarcasm.