Duration and intensity of occupational lifting and risk of long-term sickness absence: Prospective cohort study with register follow-up among 45 000 workers.

Objective: This study aimed to investigate the prospective association of lifting duration and lifting load with the risk of long-term sickness absence (LTSA).

Methods: We followed manual workers with occupational lifting (N=45 346) from the Work Environment and Health in Denmark Study (2012-2018) for two years in a high-quality national register on social transfer payments (DREAM). Cox regressions with model-assisted weights were employed to estimate the risk of LTSA from lifting duration and loads.

Results: During follow-up, 9.6% of the workers had an episode of LTSA. Compared to workers with seldom lifting (reference), workers lifting ½ and ¾ of the workday had increased risk of LTSA [hazard ratios (HR) of 1.36 [95% confidence interval (CI) 1.20-1.56] and 1.22 (95% CI 1.07-1.39)], respectively. Lifting load showed a positive exposure-response association with LTSA (trend test, P<0.01), with HR for lifting 5-15, 16-29, and ≥30 kg at 1.11 (95% CI 1.02-1.22), 1.17 (95% CI 1.03-1.34), and 1.29 (95% CI 1.11-1.50), respectively. Age-stratified analyses showed increased risk of LTSA among workers ≥50 years with a high proportion of work-related lifting compared to their younger counterparts.

Conclusions: Occupational lifting for ½ the workday increased the risk of LTSA, while higher occupational lifting load exacerbated this risk in an exposure-response manner. The study underscores the importance of reducing both lifting duration and loads for prevention of LTSA at the workplace, especially among older workers.