Do people with Alzheimer's disease need stronger heat to report pain even when its unpleasantness is similar?

Details

People with Alzheimer's disease (AD) have been shown to receive less pain medication and report pain less often than healthy controls. It is unknown whether this reflects less perceived pain, an inability to recognize pain, or an inability to communicate pain.

To examine aspects of pain processing in AD, researchers conducted a cross-sectional study of sex-matched adults aged ≥65 years with and without AD. The AD group included 40 participants, including 20 women, with a median age of 75 years; the control group included 40 participants, including 20 women, with a median age of 70 years. They compared psychophysical responses to contact-evoked heat thresholds for perceiving warmth, mild pain, and moderate pain, along with self-reported unpleasantness for each sensation.

Compared with controls, participants with AD required higher temperatures to report warmth (Cohen's d = 0.64, p = 0.002), mild pain (Cohen's d = 0.51, p = 0.016), and moderate pain (Cohen's d = 0.45, p = 0.043). There were no significant between-group differences in unpleasantness ratings (p > 0.05).

The researchers concluded that people with AD were less sensitive to detecting thermal pain than controls, but did not differ in their emotional response to its unpleasant aspects. They suggested that people with AD may experience greater levels of pain and potentially greater tissue or organ damage before identifying and reporting an injury. This finding may help explain less frequent pain reporting and, consequently, lower administration of analgesics in AD.