OBJECTIVES: To investigate (a) whether there is a causal link between smoking and low back pain (LBP), (b) whether smoking is uniquely associated with symptoms in the lumbar spine and (c) the role of respiratory problems in the possible link between smoking and LBP.

STUDY DESIGN: Data were collected through questionnaires in a cross-sectional study of a representative sample of the general Danish population, consisting of 1370 men and women aged 30-50 yr, with a response rate of 69%.

BACKGROUND: In some epidemiological studies (mostly those of cross-sectional design) smoking has been associated with LBP; this association, however, is not consistently present in all reports. Several theories exist that attempt to explain a possible association between the two; only rarely have these theories been systematically tested. However, cross-sectional data can also be used to obtain answers to questions relating to causes and mechanisms.

METHOD: A list of expectations was produced that related to three hypotheses previously forwarded in the epidemiological literature. The fit of the data in the present study was then considered in the light of these expectations.

RESULTS: There is evidence in favor of a causal link between smoking and some definitions of LBP. Smoking was not uniquely associated with the lumbar spine. Respiratory symptoms seemed to be positively associated with LBP but only when linked with smoking.

CONCLUSIONS: The clinical significance of these findings is limited, but it needs to be considered in future research. Abstinence from smoking may, however, be a useful means of primary prevention of certain types of LBP.

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