Association between objectively measured physical activity and body mass index with low back pain: A large-scale cross-sectional study of Japanese men

Background: The relationship between the combination of physical activity (PA) and body mass index (BMI) with low back pain (LBP) is unclear. The present study offers a cross-sectional assessment of how combinations of PA and BMI are related to LBP in Japanese men. Methods: Participants were 4022 Japanese men (mean age = 47) who underwent regular clinical examinations. PA was measured using a uniaxial accelerometer and divided into tertiles (PA_high, PA_middle, PA_low). A self-administered questionnaire was used to report on persistent LBP experience, drinking and smoking habits, and any existing lifestyle diseases. After covariance adjustment, a logistic regression model was used to assess how combinations of PA and BMI are related to persistent LBP. Results: 428 of the participants had persistent LBP. A clear negative dose-response relationship was found between PA levels and persistent LBP (P for linearity = 0.012). Regarding BMI, odd ratios were shown to be higher in the overweight/obese category (BMI ≥ 25 kg/m²) than for the normal weight category (BMI < 25 kg/m²). When the PA_high was taken as the reference in the normal weight category, odds ratios for PA_low and PA_middle in the normal weight category were shown to be high. Moreover, in the overweight/obese category, odd ratios for every fitness level were also high as for the normal weight category. Conclusion: The present study showed that both PA and BMI are related to persistent LBP. Also, the prevalence of persistent LBP became higher when PA_low and high BMI are combined rather than the group of PA_high and low BMI combination.