To explore the underlying mechanisms between organisational downsizing and deterioration of health of employees. Longitudinal cohort study. Data were assembled from before downsizing (time 1); during major downsizing affecting some job categories (time 2); and after downsizing (time 3). Contributions of changes in work, support, and health related behaviours between time 1 and time 2 to the relation between downsizing and sickness absence at time 3 were assessed by multilevel modelling. Mean length of follow up was 4.9 years. Raisio, a town in Finland. 764 municipal employees who remained in employment after downsizing. Records of absences from work from all causes with medical certificate. Downsizing was associated with negative changes in work, impaired support from spouse, and increased prevalence of smoking. Sickness absence rate from all causes was 2.17 (95% confidence interval 1.54 to 3.07) times higher after major downsizing than after minor downsizing. Adjustment for changes in work (for instance, physical demands, job control, and job insecurity) diminished the relation between downsizing and sickness absence by 49%. Adjustments for impaired social support or increased smoking did not alter the relation between downsizing and sickness absence. The findings were unaffected by sex and income. The exploration of potential mediating factors provides new information about the possible causal pathways linking organisational downsizing and health. Downsizing results in changes in work, social relationships, and health related behaviours. The observed increase in certificated sickness absence was partially explained by concomitant increases in physical demands and job insecurity and a reduction in job control. A considerable proportion of the increase, however, remained unexplained by the factors measured.
