Comparison of the work ability index and the work ability score for predicting health-related quality of life

Purpose To compare the relationship of the 7-item Work Ability Index (WAI) and the single-item Work Ability Score (WAS) with individual and work-related factors, and to investigate the predictive role of these two work ability assessments for health-related quality of life (HRQOL). Methods This is a cross-sectional study. 407 of 445 employees working on a construction project in Shiraz, Iran consented to participate in an anonymous survey. 381 surveys were returned completed. Correlation analyses were used to evaluate relationships between WAI and WAS, and the total score and four domains of the WHOQOL-BREF, our measure of HRQOL, and individual and work-related variables. Hierarchical multivariate linear regression analyses were performed to compare WAI and WAS in predicting HRQOL and its four dimensions. Results WAI and WAS were both significant predictors of HRQOL and its four dimensions and the explained variance was very similar. The WAI and WAS explained 46% and 44% of the variance related to the HRQOL, respectively. WAI and WAS explained 36-38% and 35-37% of the variance related to dimensions of the HRQOL, respectively. There were significant relationships of both WAS and WAI with job type, work schedule, smoking, and exercise habit. Conclusions The WAS and WAI showed a very similar relationship with participants' individual and work-related factors and HRQOL. The Work Ability Score is a valid and suitable measure for assessment of work ability among Iranian workers. Use of this simple measure could be advantageous to reduce demands on research participants and in workability assessments.