Why has the search for causes of low back pain largely been nonconclusive?

Study Design. Cross-sectional data were collected in a postal questionnaire within the framework of a 5-year randomized, controlled, prospective, population-based study. Objectives. To investigate to what extent associations differ or concur when correlates of low back pain are tested against various subdefinitions of low back pain. Summary of Background Data. Numerous factors have been suspected to cause low back pain, but findings have not been constantly reproduced in epidemiologic studies. Methods. Data were collected on 746 people reporting nonspecific low back pain some time during the year preceding the survey. Six correlates of low back pain (age, sex, marital status, attitude to a healthy life-style, self-reported physical activity at work, and smoking) were cross-tabulated against nonspecific low back pain and against four subgroups of low back pain. Results. There was only one statistically significant strong association between the potential risk indicators and the nonspecific definition of low back pain, but several emerged when the low back pain group was split into subgroups. Different subgroups of low back pain did, indeed, relate differently to the various correlates. Conclusions. It is necessary to define some clinically relevant subgroups of low back pain to accelerate the search for causal mechanisms.