Association of Back Pain with All-Cause and Cause-Specific Mortality Among Older Women: a Cohort Study.

ABSTRACT

BACKGROUND: The impact of back pain on disability in older women is well-understood, but the influence of back pain on mortality is unclear. OBJECTIVE: To examine whether back pain was associated with all-cause and cause-specific mortality in older women and mediation of this association by disability. DESIGN: Prospective cohort study. SETTING: The Study of Osteoporotic Fractures. PARTICIPANTS: Women aged 65 or older. MEASUREMENT Our primary outcome, time to death, was assessed using all-cause and cause-specific adjusted Cox models. We used a four-category back pain exposure (no back pain, non-persistent, infrequent persistent, or frequent persistent back pain) that combined back pain frequency and persistence across baseline (1986-1988) and first follow-up (1989-1990) interviews. Disability measures (limitations of instrumental activities of daily living [IADL], slow chair stand time, and slow walking speed) from 1991 were considered a priori potential mediators. RESULTS: Of 8321 women (mean age 71.5, SD = 5.1), 4975 (56%) died over a median follow-up of 14.1 years. A higher proportion of women with frequent persistent back pain died (65.8%) than those with no back pain (53.5%). In the fully adjusted model, women with frequent persistent back pain had higher hazard of all-cause (hazard ratio [HR] = 1.24 [95% CI, 1.11-1.39]), cardiovascular (HR = 1.34 [CI, 1.12-1.62]), and cancer (HR = 1.33, [CI 1.03-1.71]) mortality. No association with mortality was observed for other back pain categories. In mediation analyses, IADL limitations explained 47% of the effect of persistent frequent back pain on all-cause mortality, slow chair stand time, and walking speed, explained 27% and 24% (all significant, p < 0.001), respectively. LIMITATIONS: Only white women were included. CONCLUSION: Frequent persistent back pain was associated with increased mortality in older women. Much of this association was mediated by disability.