Epidemiological profiles of chronic low back and knee pain in middle-aged and elderly Japanese from the Murakami cohort

Purpose: Epidemiological profiles of chronic low back and knee pain have not been studied extensively. This study aimed to determine the prevalence of and potential risk factors associated with chronic low back and knee pain in middle-aged and elderly Japanese. Methods: This cross-sectional study involved 14,217 community-dwelling individuals aged 40-74 years living in the Murakami area of Japan. A self-administered questionnaire was used to obtain information regarding marital status, education level, occupation, household income, and body size. Participants also reported current chronic pain, if any, by site arid degree of severity, using the verbal rating scale of the Short Form 36. Results: The prevalence of moderate-very severe chronic pain was 9.7% in the low back, 6.7% in the knee, 13.9% in either the low back or knee, and 2.6% in both the low back and knee. Multivariate analysis revealed that lower education level, lower income, and manual occupation in men and older age and higher body mass index in women were significantly associated with a higher prevalence of chronic low back pain. In both sexes, older age, lower education level, and higher body mass index were significantly associated with a higher prevalence of knee pain. Regarding sex differences, adjusted ORs of chronic pain of the low back and knee for women were 0.85 (95% CI 0.75-0.97) and 1.27 (95% CI 1.09-1.49), respectively. Conclusion: Nearly 14% of middle-aged and elderly individuals had moderate very severe chronic pain of the low back or knee, and this pain was associated with many demographic factors, including sex, age, education level, household income, occupation, and body size.