The results emphasize the role of psychosomatic and psychological factors in the occurrence and course of ND for various dimensions of the disorder.

Objectives-To test associations between non-specific low back pain and several risk factors when definitions of low back pain vary. Design/setting/participants-A cross sectional study was set up in 1991, 725 workers from four occupational sectors answered a self administrated questionnaire including the Nordic questionnaire and questions about intensity of pain and individual and occupational factors. Main results-Prevalence of low back pain varied from 8% to 45% according to the definition used. Psychosomatic problems, bending or carrying loads were often associated to low back pain, whereas other risk factors were related to some specific dimensions of the disorder. Conclusions-Risk factors of low back pain vary with the definition. This could explain inconsistencies found in literature reviews. To be able to compare data, it seems important to be precise what definition is used and to use comparable questionnaires. (J Epidemiol Community Health 2000;54:215-220) Non-specific low back pain (LBP) is a common health problem, which has several definitions most often based on answers to questionnaires, use of medical services or sick leave. Many epidemiological studies have been carried out in order to specify the role of individual and occupational factors as possible causes. However, many results are inconsistent. Burdorf and Sorock 1 listed potential risk factors with positive or negative association in a selection of 35 publications. In this review, no individual risk factor could be clearly pointed out: results on the role of age, gender and obesity showed inconsistent evidence. More consistency in the results is observed for work related risk factors, such as lifting, twisting, bending, exposure to whole body vibration or prolonged postures. [2][3][4]