Physical activity and time spent sitting as a risk factor for low-back pain: longitudinal data from the HUNT study
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Background: Low back pain (LBP) is the most common pain condition with a lifetime prevalence of 70 %. One of the most investigated risk factor for LBP is sedentary lifestyle. This is of great interest as sitting is the more dominant occupational activity in today’s society. Aim: The aim of this study was to prospectively investigate if the risk of chronic LBP is associated with time spent sitting, leisure time physical activity, and occupational activity. We also examined the combined effect of time spent sitting and physical activity and also for the combined effect of physical leisure activity and work activity on the risk of chronic LBP. Method: Logistic regression was used to calculate odds ratio (OR) of LBP associated with the various activity measures. The precision of the estimates was assessed by 95 % confidence interval (Cl). Results: There was some evidence of an inverse association between time spent sitting and risk of chronic LBP, with a OR of 0.83 (0.71-0.97) among persons sitting more than eleven hours a day compared to persons sitting less than five hours a day. Hard physical labour increased the odds of chronic LBP (OR 1.19, 1.02-1.40) when compared to an occupation mostly involving sitting, whereas high levels of leisure time activity was associated with a OR of 0.79 (0.64 - 0.96) compared to being inactive. Combined analysis showed high level of leisure time physical activity to decrease the risk of chronic LBP regardless of occupation. The largest modification of leisure time physical activity on the risk of chronic LBP was found for persons having hard physical work demands. Conclusion: In this population-based longitudinal study, time spent sitting and leisure time physical activity was inversely associated with chronic LBP, whereas heavy physical work, such as walking, lifting and heavy labour, increased the risk. Moreover, analyses of combined effects suggest that the lowest risk was among persons who reported high leisure time physical activity and much sitting.