Pain as a risk factor for disability or death.

OBJECTIVES: To determine whether pain predicts future activity of daily living (ADL) disability or death in individuals aged 60 and older.
DESIGN: Prospective cohort study.
SETTING: The 1998 to 2008 Health and Retirement Study (HRS), a nationally representative study of older community-living individuals. PARTICIPANTS: Twelve thousand six hundred thirty-one participants in the 1998 HRS aged 60 and older who did not need help in any ADL. MEASUREMENTS: Participants reporting that they had moderate or severe pain most of the time were defined as having significant pain. The primary outcome was time to development of ADL disability or death over 10 yrs, assessed at five successive 2-year intervals. ADL disability was defined as needing help performing any ADL: bathing, dressing, transferring, toileting, eating, or walking across a room. A discrete hazards survival model was used to examine the relationship between pain and incident disability over each 2-year interval using only participants who started the interval with no ADL disability. Several potential confounders were adjusted for at the start of each interval: demographic factors, seven chronic health conditions, and functional limitations (ADL difficulty and difficulty with five measures of mobility).
RESULTS: At baseline, 2,283 (18%) participants had significant pain. Participants with pain were more likely (all P < .001) to be female (65% vs 54%), have ADL difficulty (e.g., transferring 12% vs 2%, toileting 11% vs 2%), have difficulty walking several blocks (60% vs 21%), and have difficulty climbing one flight of stairs (40% vs 12%). Over 10 years, participants with pain were more likely to develop ADL disability or death (58% vs 43%, unadjusted hazard ratio (HR) = 1.67, 95% confidence interval (CI) = 1.57-1.79), although after adjustment for confounders, participants with pain were not at greater risk for ADL disability or death (HR = 0.98, 95% CI = 0.91-1.07). Adjustment for functional status almost entirely explained the difference between the unadjusted and adjusted results.
CONCLUSION: Although there are strong cross-sectional relationships between pain and functional limitations, individuals with pain are not at higher risk of subsequent disability or death after accounting for functional limitations. Like many geriatric syndromes, pain and disability may represent interrelated phenomena that occur simultaneously and require unified treatment paradigms.