Objectives The determinants of poor functioning and subsequent early exit from work are well established but very little is known about the positive determinants of maintaining good functioning among the ageing workforce. We investigated modifiable determinants of maintaining good mental and physical health functioning.

Methods We used prospective survey data collected across four waves among the midlife employees of the City of Helsinki, Finland, 2000–2017 (n=3342). Health functioning was repeatedly measured using the Short Form 36 (SF-36) inventory. Trajectories of mental and physical health functioning were separately examined using group-based trajectory analysis. Multinomial logistic regression models were fitted to examine determinants of each trajectory.

Results Four trajectory solutions for the developmental patterns in health functioning during the follow-up period were selected, with a slightly different shape of the first trajectory for mental and physical functioning: (1) continuously low (mental), low and decreasing (physical), (2) increasing, (3) decreasing and (4) continuously high functioning. After adjustments, the employees in the continuously high mental health functioning group were more likely to have optimal job demands, high job control, no sleep problems and no binge drinking behaviour. Employees in the continuously high physical functioning group had more likely low levels of physically strenuous work and hazardous working environment and no sleep problems and normal weight.

Conclusion High job control, good sleep and avoiding binge drinking may help maintain good mental health functioning. Low levels of physical or environmental work exposures, good sleep and recommended healthy weight may support maintenance of good physical health functioning among ageing employees.