Frequent back pain and subsequent mortality among older community-dwelling white women in the study of osteoporotic fractures (SOF)
Roseen, Eric Jon
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INTRODUCTION: While the impact of back pain on morbidity in older adults is well-understood, the influence of back pain on mortality is unclear. Back pain is the leading cause of disability worldwide, and disability is associated with elevated risk of mortality. Thus, we hypothesized that older women with persistent back pain would have a higher risk of mortality over 16-years of follow-up, compared to those with no back pain among participants in the Study of Osteoporotic Fractures (SOF), a large multisite cohort study. Furthermore, we hypothesized that limitations of Instrumental Activities of Daily Living (IADLs) would mediate a greater proportion of the mortality risk, compared to two objective measures of physical function, walking and chair stand speed. METHODS: The analytic sample included 8,321 SOF participants (mean age 71.5, SD=5.1) who answered back pain questions at baseline (1986–87) and visit 2 (1989–90). We created a four-category back pain variable by combining responses at two interviews (baseline and visit 2). Categories included: no back pain (24%), non-persistent back pain (23%), and infrequent (44%) or frequent (9%) persistent back pain. Participants were followed from visit 2 through visit 9 (2006–08). Death was confirmed with receipt of death certificates. Using Cox-proportional hazards, we calculated hazard ratios (HR) and 95% confidence intervals (CI) for all-cause and cause-specific mortality with the ‘no back pain’ participants as our reference group. We adjusted for age, sociodemographic characteristics, self-reported general health, smoking status, comorbid conditions (e.g., prevalent vertebral fractures, osteoarthritis, hip pain, diabetes, hypertension), previous stroke, history of breast cancer, hospitalizations and falls in the previous year. We evaluated self-reported IADL limitations, slow walking speed, and slow chair stand time as a priori mediators of back pain and subsequent mortality. RESULTS: A total of 4975 women (55.8%) died over the follow-up period. A higher proportion of women with frequent persistent back pain died (65.8%) compared to those with no back pain (53.5%) (adjusted HR = 1.24; 95% CI 1.11 to 1.39). We observed an increase in cardiovascular (adjusted HR = 1.34; 95% CI 1.12 to 1.62) and cancer (adjusted HR = 1.33; 95% CI 1.03 to 1.71) mortality. No increased risk was observed for other back pain groups. A larger proportion of the association was mediated by IADL limitations (47%), compared to poor performance on chair stand (27%) and walking speed (24%). CONCLUSION: Compared to older women with no back pain, those with frequent persistent back pain had an increased risk of mortality, which underscores the importance of developing safe interventions to address and prevent this condition. Therapies that address IADL limitations or improve physical function (e.g. walking speed, chair stand) may be ideal for preventing early death in individuals with back pain.