Background Physical workload factors have been linked to the risk of sickness absence, however, some work exposures can also be protective of work ability. We aimed to first identify sickness absence trajectories in a nationally representative occupational cohort, and second to examine the associations between physical workload factors, potential protective factors and sickness absence trajectories.

Methods We examined a nationally representative cohort of working aged Finnish adults interviewed and medically examined at baseline in 2000–2001 (n=3814). Both potentially protective (sitting and keyboard use) and risk factors (e.g. handling of heavy loads and vibration) were included. All medically confirmed sickness absence periods 2002–2008 were included in the trajectory analyses to identify latent groups with similar sickness absence trends. These data were derived from the registers of the Social Insurance Institution of Finland. The models were adjusted for sociodemographic factors, health behaviors and physical and mental health.

Results We found a group with a very low level, a group with a stable low level, and a group with a high and increasing level of sickness absence. After full adjustments, prolonged sitting and use of keyboard emerged as protective factors that were associated with a lower risk of belonging to the trajectory with high and increasing sickness absence (HR 0.60; 95% CI 0.45–0.80). In turn, the risk increased with the number of physical workload factors reported, and was highest for those with four or more workload factors (HR 2.84; 95% 2.08–3.88).

Conclusions Physical work is associated with the risk of long-term sickness absence, with the highest risk found for those with several different physical workload factors. As the risk remained after controlling for various pertinent risk factors, this highlights the need to find ways to better maintain work ability of those with the physically most strenuous work.