Physical activity as mediator between back pain and disability.

The objective was to explore the mediating role of leisure-time physical activity on the correlation between back pain and disability. A mediation analysis was conducted among the cross-sectional sample of 1330 patients in outpatient clinic. The average age was 47.6 years and 64% were women. For the entire sample, the mediating effect of physical activity remained below 10% of the total effect. The mediating effect was significantly greater among women comparing to men - up to 19.0% [95% confidence interval (CI) 10.4-27.6%] versus 2.3% (95% CI 0.0-6.1%). The effect did not significantly differ based on age, BMI, or educational or professional status. Some insignificant trends, however, could be seen - the effect was possibly stronger among patients with higher educational level and those with higher BMI. The results suggested that while physical activity seems to be a weak mediator, its mediating role might vary across different groups of patients with back pain. This variation should be taken into account when planning rehabilitation measures for people with back pain.