Variable Age category 18–39 years 40–49 years 50–68 years Female worker Psychosocial work demands Lack of job control Poor skill discretion High work demand Physical work demands Manual materials handling Awkward back postures Static working postures Repetitive movements Bending or twisting upper body Work ability score Excellent Good Moderate Poor Productivity loss (score <10) Table 2 Univariate and multi- variate associations of work ability dimensions and produc- tivity loss at work among 10,542 workers * p < 0.05 123 loss were most inXuenced by the dimensions ‘general work ability’ (dimension 1), ‘work ability in relation to physical and mental demands’ (dimension 2), and ‘prognosis of work ability’ (dimension 6) (Table 2). The four health- related dimensions (number of diagnosed diseases, subjec- tive estimation of work impairment due to disease, sickness absence during the past year, and psychological resources) did not remain signiWcant in the multivariate model, when adjusted for other dimensions. Older workers and women showed inverse associations with productivity loss at work (Table 3). The psychosocial 708 Table 1 Individual characteristics, work-related factors, work ability index, and productivity loss at work among 10,542 workers in the Netherlands WAI dimension Mean (SD) Productivity loss (1/0) General work ability (0–10) Work ability in relation to physical and mental demands (2–10) Diagnosed diseases (1–7) Impairment due to diseases (1–6) Sickness absence (1–5) Prognosis work ability (1, 4, 7) Psychological resources (1–4) 8.18 (1.60) 8.29 (1.22) 4.66 (1.82) 5.11 (1.31) 4.19 (0.95) 6.56 (1.27) 3.43 (0.65) Univariate Multivariate OR 0.68* 0.69* 0.91* 0.82* 0.80* 0.84* 0.64* 95% CI 0.66–0.70 0.66–0.71 0.89–0.93 0.79–0.84 0.77–0.84 0.82–0.87 0.60–0.68 OR 0.73* 0.87* – – – 0.96* – 95% CI 0.70–0.76 0.83–0.91 0.93–0.99 Frequency (%) 33.5 (N = 3,529) 34.4 (N = 3,627) 32.1 (N = 3,386) 42.8 (N = 4,512) 59.4 (N = 6,266) 73.5 (N = 7,747) 58.7 (N = 6,189) 6.4 (N = 671) 13.7 (N = 1,447) 43.8 (N = 4,621) 46.2 (N = 4,873) 33.3 (N = 3,510) 32.8 (N = 3,454) 47.4 (N = 4,999) 16.4 (N = 1,730) 3.4 (N = 359) 44.3 (N = 4,666) Int Arch Occup Environ Health (2011) 84:705–712 factors lack of job control, high workload, and poor skill discretion were associated with productivity loss at work, with odds ratios remaining quite comparable in the multi- variate analysis. The physical factors awkward back pos- tures, static working postures, and repetitive movements showed statistically signiWcant associations in the univari- ate analyses, which did not remain signiWcant in the multi- variate analysis. None of the physical work demands had a signiWcant contribution in the multivariate model with ORs varying from 1.01 to 1.03. Table 4 shows the joint eVects of psychosocial work factors and work ability on productivity loss at work. For all three psychosocial factors and work ability, the joined eVect was strongly associated with productivity loss at work than the single eVects of both variables. The RERI for job control was 0.63 (0.11–1.16), for skill discretion 0.24 (¡0.31–0.79), and for work demand ¡0.07 (¡0.65–0.51). As zero was outside the conWdence interval for lack of job control, the interaction between decreased work ability and lack of job control was statistically signiWcant. In other words, we found a statistically signiWcant additive interac- tion between lack of job control and decreased work ability for the association with productivity loss. RERI can then be interpreted as the proportion of productivity loss at work among those workers with decreased work ability and lack of job control that is attributable to their interaction. Within workers with a good work ability, the presence of lack of job control was associated with a 23% increase in likelihood of productivity loss at work. Within workers with a decreased work ability, lack of job control had a 38% increase in the occurrence of productivity loss at work. Discussion Decreased work ability showed statistical signiWcant asso- ciations with productivity loss at work, especially in combi- nation with lack of job control. In other words, job control