Association between low back pain and functional disability in the elderly people: a 4-year longitudinal study after the great East Japan earthquake

BACKGROUND: Functional disability is a major health issue in an aging population. Low back pain (LBP) is a common health concern that can lead to functional disability in the elderly; nonetheless, their association has not yet been clarified. This study aimed to examine the association between LBP and functional disability in the elderly, with a focus on its dose-dependent effects. METHODS: This study used the 4-year longitudinal data of people living in disaster-affected areas after the Great East Japan Earthquake (aged ≧65, n = 914). LBP and physical function were assessed at 2, 4, and 6 years after the disaster. Multivariate logistic regression analyses were performed to assess the association between LBP and low physical function, as well as the effect of preceding LBP on the onset of low physical function. RESULTS: LBP was significantly associated with low physical function, and the association became stronger as the duration of LBP increased. Adjusted odds ratios (95% confidence intervals) were 1.27 (0.79–2.06) in “< 2 years,” 1.95 (1.01–3.77) in “≥2 years and <4 years,” and 2.34 (1.35–4.06) in “≥4 years” (p for trend = 0.009). Additionally, preceding LBP was significantly associated with the onset of low physical function, and the effect became prominent as the duration of LBP increased. Adjusted odds ratios (95% confidence intervals) were 2.28 (1.19–4.37) in “< 2 years” and 2.82 (1.35–5.90) in “≥2 years” (p for trend = 0.003). CONCLUSIONS: LBP is associated with physical disability among the elderly in a dose-dependent manner. Therefore, prevention and treatment of LBP are important for preventing functional disability. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12877-022-03655-7.