[The association between physical workload and low back pain clouded by the "healthy worker" effect].
BACKGROUND
Both physical and psychosocial workplace factors are considered risk factors for low back pain (LBP). However, today, no consensus has been reached regarding the exact role of these factors in the genesis of LBP.


METHODS
Questionnaire data were collected at baseline for 1,397 (and after five years for 1,163) men and women aged 31-50 years at baseline. LBP (any LBP within the past year; LBP < or = 30 days in total during the past year; LBP > 30 days in total during tha past year) was analysed in relation to physical workload (sedentary, light physical, and heavy physical work) using logistic regression and controlling for age, gender, and social group. The proportions af workers changing between the workload groups over the five-year period were analysed in relation to LBP status.


RESULTS
A baseline no statistically significant differences in LBP outcomes were found for workers exposed to sedentary, light physical, or heavy physical work. This was true for both genders and all age and social groups. At follow-up these was a statistically significant dose-response association between any LBP and long-standing LBP during the past year and increasing physical workload at baseline, also after controlling for age, gender and social group. Subjects with a heavy physical workload at baseline changed significantly more often to sedentary work, if they had experienced LBP for more than 30 days out of the past year.


CONCLUSIONS
Having a sedentary job might have a protective or neutral effect in relation to LBP, whereas having a heavy physical job constitutes a significant risk factor. Because og migration between exposure groups (the "healthy worker" effect), longitudinal studies are necessary for investigating the associations between physical workload and LBP.
Hartvigsen
Jan
J
Nordisk Institut for Kiropraktik og Klinisk Biomekanik, Klosterbakken 20, DK-5000 Odense.
Bakketeig
Leif S
LS
Leboeuf-Yde
Charlotte
C
Engberg
Marianne
M
Lauritzen
Torsten
T
D000328:Adult; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D015989:Healthy Worker Effect; D006801:Humans; D017116:Low Back Pain / Q000453:epidemiology* / Q000209:etiology / Q000523:psychology; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors; D012737:Sex Factors; D012923:Social Class; D011795:Surveys and Questionnaires; D016526:Workload
Sammenhaengen mellem fysisk arbejdsbelastning og laenderygsmerter sløres af "healthy worker"-effekten.