Papers of the Week

The purpose of this article was to examine age-related changes in conditioned pain modulation (CPM) and temporal summation of pain (TS) using meta-analytic techniques. Five electronic databases were searched for studies that compared measures of CPM and TS between healthy, chronic pain-free younger, middle-aged, and older adults. Eleven studies were included in the final review for TS and 11 studies were included in the review of CPM. The results suggested a moderate magnitude of difference in TS between younger adults and middle-aged/older adults, with the older cohorts exhibiting enhanced TS of pain. Considerable variability existed in the magnitude of the effects sizes, which was likely due to the different experimental methodology used across studies (i.e., inter-stimulus interval, stimulus type, body location). In regards to CPM, the data revealed a large magnitude of difference between younger and older adults, with younger adults exhibiting more efficient pain inhibition. Differences in CPM between middle-aged and older adults were minimal. The magnitude of pain inhibition during CPM in older adults may depend on the use of concurrent vs. non-concurrent protocols. In summary, the data provided strong quantitative evidence of a general age-related decline in endogenous pain modulatory function as measured by TS and CPM. PERSPECTIVE: This review compared conditioned pain modulation and temporal summation of pain between younger, middle-aged, and older adults. These findings enhance our understanding of the decline in endogenous pain modulatory function associated with normal aging.