Work correlates of back problems and activity restriction due to musculoskeletal disorders in the Canadian national population health survey (NPHS) 1994-5 data

Objectives-To describe the prevalence of musculoskeletal problems in the Ca nadian working population and to determine cross sectional associations bet ween such problems and work factors, particularly job strain and physical d emand variables. Methods-The Canadian 1994 national population health survey (NPHS) sampled 4230 working men and 4043 working women (ages 18-64) who answered an abbrev iated version of the job content questionnaire. Workers were classified int o four strain categories: high, passive, active, and low. Outcomes were res tricted activity due to musculoskeletal disorders and the diagnosis of a ba ck problem (both yes or no). Survey weights were incorporated to allow for different probabilities of selection. Logistic regression analyses were car ried out separately for women and men, controlling for sociodemographic fac tors. Results-Prevalence of chronic back problems diagnosed by a health practitio ner was 14.5% among men and 12.5% among women. Men had a 6.6% prevalence of restricted activity due to musculoskeletal disorders, whereas the correspo nding figure for women was 5.3%. Women, but not men, in high strain jobs we re more likely to report both back problems (odds ratio (OR) 1.60, 95% conf idence interval (95% Cl) 1.14 to 2.28) and restricted activity (OR 1.98, 95 % CI 1.16 to 3.48) compared with those in low strain jobs. High physical ex ertion was an independent predictor of back problems in both sexes. For bot h men and women, low social support at work and high job insecurity were in dependent predictors of restricted activity due to musculoskeletal disorder s. Conversely, chronic back problems contributed to explanation of high job strain among women (OR 1.76, 95% CI 1.30 to 2.39) and high physical exerti on among men (OR 1.39, 95% CI 1.09 to 1.77), whereas restricted activity du e to musculoskeletal disorders contributed to explanation of high job insec urity in both sexes. Conclusions-Associations of interest between work stressors and musculoskel etal problems in this cross sectional study provide evidence for physical a nd psychosocial factors both affecting disability and being affected by dis ability in a working population.