Effects of consecutive workdays and days off on low back pain, fatigue and stress: prospective cohort study among warehouse and construction workers.

OBJECTIVES:Limited knowledge exists about day-to-day changes in physical and mental symptoms in warehouse and construction workers. This study investigated the associations between consecutive workdays and days off with low back pain (LBP) intensity, bodily fatigue and mental stress. METHODS:Participants (n=224) received daily questions for 21 days about LBP, fatigue, stress (outcome, 0-10 scales), and workdays and days off (exposure). We tested associations between 1-3 workdays (n=148) and 1-2 days off (n=158) with LBP intensity, bodily fatigue and mental stress after work and the following morning using linear mixed models with repeated measures controlling for relevant confounders. RESULTS:Consecutive workdays led to progressively increased LBP intensity, with three workdays increasing LBP intensity by 1.76 (95% CI 1.48 to 2.03) points. Bodily fatigue and mental stress increased after one workday (2.06 (95% CI 1.80 to 2.32) and 0.97 (95% CI 0.77 to 1.17) points, respectively) and remained stable for three workdays. After 1 day off, bodily fatigue and mental stress decreased -1.82 (95% CI -2.03 to -1.61) and -0.88 (95% CI -1.05 to -0.71) points, respectively, without decreasing further. In contrast, LBP intensity decreased progressively -1.09 (95% CI -1.27 to -0.91) and -1.45 (95% CI -1.67 to -1.24) points after 1 and 2 days off, respectively. CONCLUSIONS:Workdays and days off affected the outcome variables differently. LBP intensity progressively increased with consecutive workdays, while workers needed 2 days off to recover. This study provides valuable knowledge about how to organise the workweek to prevent LBP, fatigue and stress, potentially reducing labour market withdrawal.