Occuptational sitting and low back pain

Abstract

Objectives To determine if there is an association between low back pain (LBP) and time spent sitting at work in employees of a UK train operating company. Design Case control study comparing the frequency of exposure to sitting in different groups. Method A total of 299 cases out of a study population of 4782 were identified. Both cases and controls were taken from the same population of employees of a UK train operating company. Eligible cases were incident episodes of LBP identified among employees during a one year period using sickness absence data. Controls were all those that did not have LBP identified in the same period. Job role was used as the basis for assigning sitting exposure through expert assessment. The aim was to arrive at a reasonable numerical estimate of the exposure for each role. Cases and controls were compared at different levels of exposure. The odds ratio and confidence interval were calculated at each level. Sitting zero hours was taken as the baseline category to see if there was a trend of increasing LBP with increasing sitting exposure. Time to return to work was also calculated for all cases at each exposure level. Main outcome measures Sickness absence due to LBP and time to return to work.

Results A U-shaped association was found between occupational sitting time and LBP. The optimal level of sitting was found to be two hours per day with a statistically significant protective effect compared to no sitting (OR=0.62, 95% CI 0.44-0.87). The probability of LBP increased when sitting for longer periods, although this was not statistically significant (four hours OR=1.24, 95% CI 0.94-1.62; six hours OR=1.46, 95% CI 0.89-2.39). There was also a trend for employees to take longer to return to work in roles where less time was spent sitting at work. Conclusions Both too much sitting and too little sitting have consequences for LBP. The optimal level of sitting appears to be two hours per day. Further research is recommended using a prospective design and directly measured sitting time to confirm the findings of this study. Time to return to work also seemed to vary according to sitting exposure. Further research is recommended to explore the determinants of return to work. Keywords Low back pain; occupational sitting; sickness absence.