Objectives To identify trajectories of work ability from pre-COVID to post-COVID-19 pandemic period and to examine work unit characteristics associated with these trajectories.

Methods The study population was a cohort of Finnish public sector employees (n=54 651) followed from 2016 until 2022. We used trajectory analysis to identify trajectories of work ability and multinomial regression to examine their associations with prepandemic work unit characteristics and pandemic-related changes at workplaces.

Results We identified three trajectories of work ability: (1) suboptimal work ability decreasing over time (12%); (2) relatively consistent good work ability (73%) and (3) consistent optimal work ability (15%). The strongest associations with belonging to the suboptimal work ability trajectory were found for employees in work units characterised by high job strain (OR 2.29, 95% CI 1.82 to 2.88), poor team climate (OR 0.74, 95% CI 0.64 to 0.86) and low organisational justice (OR 0.64, 95% CI 0.57 to 0.72) when compared with the most optimal trajectory. The least favourable work ability trajectory was also associated with team reorganisation (OR 1.22, 95% CI 1.04 to 1.44) and a low share of those working from home (OR 0.86, 95% CI 0.78 to 0.94) during the pandemic.

Conclusion Prepandemic psychosocial risk factors and pandemic-induced changes at work were associated with poor and declining work ability during the COVID-19 pandemic. Employers and occupational health services should better identify and support vulnerable employees to enhance their work participation.