Introduction

Low back pain (LBP) is a major global health challenge. Sitting is a suggested risk factor for LBP among blue-collar workers. Previously, information on sitting time has been collected by self-reports, being imprecise and biased compared to objective measurements. Therefore, we aimed at investigating the association between objectively measured sitting time and LBP among blue-collar workers.

Methods

The analysis is based on the DPHACTO cohort, and included 601 Danish blue-collar workers recruited from the cleaning, manufacturing and transport sector. Cross-sectional information on LBP intensity (range 0-10) was collected by questionnaire. Objective measurements of sitting were collected using two accelerometers (ActiGraph GT3X+) worn on the thigh and trunk during 1-5 workdays. Sitting time were split in occupational and leisure time and analyzed as the total duration, and divided in temporal patterns of uninterrupted long (> 30 min), moderate (> 5 – 30 min) and short (< 5 min) bouts by the exposure variation analysis method. Association between sitting and LBP intensity was analyzed using univariate ANOVA adjusted for age, sex, smoking, BMI, job seniority and occupational lifting and carrying activities. Additionally, total sitting were adjusted for physical activities (standing, walking, running, walking in stairs and biking) and sitting in opposite domain (occupational/leisure); and temporal pattern variables were mutually adjusted for other lengths of sitting bouts.

Results

No associations were seen between total sitting time and LBP; (occupational B=0.017, p=0.53; leisure B=0.008, p=0.76). No associations seen between long (occupational B=-0.002, p=0.97; leisure B=0.010, p=0.75), moderate (occupational B=0.025, p=0.50; leisure B=0.006, p=0.90), or short (occupational B=0.035, p=0.63; leisure B=-0.009, p=0.95) bouts of uninterrupted sitting and LBP.

Conclusions and implications

Objectively measured sitting time was not associated with LBP in blue-collar workers; pointing toward other factors being attributed to LBP. Thus, this finding needs to be investigated in prospective designs.