Psychometric Properties of the Spanish Version of the Work Ability Index in Working Individuals.

It is increasingly important to have validated instruments to assess the ability to work. Thus, the aim of this study was to evaluate the psychometric properties of the Spanish version of the Work Ability Index (WAI) in working individuals. A cross-sectional study was conducted on 360 workers (men and women) in a high-complexity public hospital and in a public university. The participants were between 40 and 75 years, with a contract of at least 11 h weekly. The ability to work was assessed using the WAI and the perception of health through the Short Form 36 Health Survey version 2 (SF-36 v2). The concurrent validity was analyzed, correlating the WAI with the SF-36 v2. An exploratory factor analysis was performed to test construct validity. In addition, the internal consistency of the WAI was analyzed using the standardized Cronbach's alpha coefficient. The WAI showed a positive and statistically significant correlation (p < 0.001) with the SF-36 v2. The exploratory factor analysis showed three factors interpreted as, "Mental Resources", "Diseases and Health-Related Restrictions", and "Self-perception of Work Ability". The reliability of the factors was acceptable, except for the second factor, which was poor. The WAI demonstrated acceptable psychometric properties, such as internal consistency, concurrent and construct validity, constituting a reliable instrument to measure work ability for the population of active working individuals in the service sector.