A Nine-Year Population-Based Prospective Cohort Study
Study Design. Population based prospective cohort study.Objective. We explored the cross-sectional relationships between lumbar multifidus (LM) intramuscular adipose tissue (IMAT) infiltration and LBP at three successive time points and investigated the role of IMAT in predicting the occurrence of LBP after five and nine years.Summary of Background Data. Although low back pain (LBP) is a major source of disease burden, the biologic determinants of LBP are poorly understood.Methods. Participants were 40-year-old adults randomly sampled from a Danish population and followed-up at ages 45 and 49. At each time point, participants underwent magnetic resonance imaging and reported ever having had LBP, LBP in the previous year, non-trivial LBP in the previous year, or a history of pain radiating into the legs. Pixel intensity and frequencies from T1-weighted magnetic resonance images identified the greatest proportion of LM IMAT at the L4 and L5 spinal levels. IMAT infiltration was categorised as normal/mild, moderate, or severe based on tertile divisions. Associations were explored with crude and adjusted odds ratios (aOR) from logistic regression models. Model covariates included sex, body mass index and occupational and leisure time physical activity.Results. 401 participants were enrolled, with 331(83%) and 286(71%) participants followed-up at five and nine years respectively. The cross-sectional analyses demonstrated that at age 40, participants with severe IMAT infiltration demonstrated increased odds of ever experiencing LBP (aOR[95%CI] = 3.16[1.45,6.89]), non-trivial LBP (aOR[95% CI] = 2.82[1.36,5.81]), LBP in the past year (aOR[95% CI] = 1.95[1.07,3.53]) and leg pain (aOR[95% CI] = 2.08[1.19,3.62]). There were no consistent cross-sectional associations between LBP/leg pain and LM IMAT at age 45 or age 49 and LM IMAT did not predict future LBP.Conclusion. The relationship between LM IMAT and lbp/leg pain is inconsistent and may be modified by age.