Work Ability Index (WAI)
In plain English
Work Ability Index (WAI) is a multi-item scale (7 dimensions). What it claims to measure: Self-assessed work ability, defined as the balance between an individual's personal resources (health, competence, values) and the physical and mental demands of their work. Licence for an employer or vendor: could not be verified against the steward's current terms; no class is asserted.
The published evidence is strongest for criterion validity against organisational outcomes (absence, turnover, performance); moderate for structural validity, convergent and discriminant validity, internal consistency and test-retest reliability. No published evidence was located for measurement invariance and responsiveness to change: the registry searched and found none in the sweep to date, so if you need those properties evidenced, this instrument does not yet carry them. Criterion validity against a reference standard does not apply to this construct: no reference standard exists for it, so nothing is graded and nothing is missing. The evidence base for structural validity is contested in the published literature.
Grades summarise the published evidence for this instrument on its own terms; they are not comparable across instruments, and this page makes no recommendation. Whether an instrument fits your workforce is a judgement this registry informs but cannot make. Full evidence, with citations, below. This summary is generated from the record's data, not written by hand.
Identity
Version: Standard seven-dimension WAI (10 questions across seven items/dimensions); a long form and short form are distributed by the WAI-Netzwerk.
Structure: 7 dimensions assessed via 10 questions (score range 7 to 49)
Original citation: Tuomi K, Ilmarinen J, Jahkola A, Katajarinne L, Tulkki A. Work Ability Index. Finnish Institute of Occupational Health, Helsinki (2nd revised edn 1998). Founding empirical work: Tuomi et al., Scand J Work Environ Health 1991 (see cited longitudinal municipal-employee studies Ilmarinen/Tuomi cohort).
Steward / publisher: Finnish Institute of Occupational Health (FIOH / Tyoterveyslaitos), Helsinki; German national distribution via the WAI-Netzwerk / BAuA.
Licence status: not yet verified against current steward terms. The registry's licence-currency rule requires the licence to be confirmed against the steward's current distribution terms; a primary steward licence page could not be reached at the last verification attempt. The originating steward's site (Finnish Institute of Occupational Health, FIOH / Tyoterveyslaitos, ttl.fi) and the German national steward page (BAuA, baua.de) both returned server-side 403 (Forbidden) responses to automated retrieval, so their current terms could not be read. The only reachable steward-network page, the German WAI-Netzwerk portal waiplus.online, is a commercial consultancy site marketing a trademarked survey service ('waiplus') and does not state the licence terms of the underlying WAI questionnaire. Search-result listings (not read as page content) indicate FIOH sells an official user manual ('WAI, How to use the Work Ability Index questionnaire', Rautio and Michelsen) through its bookshop and that the questionnaire is widely described in the literature as freely usable for occupational-health screening and research, but no current primary-source licence terms were confirmed. 'WAI' is presented as a trademark of FIOH. No open-content licence (Creative Commons or equivalent) should be assumed; practitioners must confirm current terms with the relevant national steward before use.
Constructs claimed
Self-assessed work ability, defined as the balance between an individual's personal resources (health, competence, values) and the physical and mental demands of their work. The index aggregates current work ability relative to lifetime best, work ability relative to job demands, number of physician-diagnosed diseases, estimated work impairment due to disease, sickness absence in the past year, own prognosis of work ability in two years, and mental resources.
Relations to other records
- has short form Work Ability Score (WAS), single-item. Single item against the full index: Spearman rs = 0.63 in 12,389 workers (El Fassi 2013); convergent validity of the single item confirmed in Swedish working samples (Ahlstrom 2010). Head-to-head, the single item discriminates less well than the full index for future sickness absence: AUC 0.67 against 0.78 (Roelen 2014). Recorded as fact; the registry does not say which form an implementer should use.
Evidence
Structural validity Moderatecontestedevidence form: canonical
direct multi-occupational sample, health-centre workers and aeronautical workers (flag basis: German multi-occupational worker study; Spanish health-centre workers; Spanish aeronautical workers)
Dimensionality is genuinely contested and the original single-score (unidimensional) scoring assumption is not well supported. A representative German confirmatory analysis (n=3968) found two correlated factors, a 'subjective work ability and resources' factor and a 'health-related' factor, fitting better than one factor (Freyer 2018). An earlier German multi-occupational worker study (n=324) likewise rejected both a one-factor and an orthogonal two-factor model, favouring a two-dimensional correlated-factor solution in which only five of seven items loaded unambiguously (Martus 2010). Spanish health-centre workers (n=1184) showed EFA support for one factor but better CFA fit for two factors (Mateo Rodriguez 2021), a pattern echoed in Spanish aeronautical workers (Gonzalez-Dominguez 2024) and a Brazilian online-application study (Pucci 2024). Three-factor solutions have also been reported in Iranian (Abdolalizadeh 2012) and Chilean/Spanish (Bascour-Sandoval 2020) samples, while a recent large Brazilian re-evaluation (n=3051) reported a unidimensional structure but with only marginal fit (RMSEA 0.125, TLI 0.900, CFI 0.882) (Martinez 2025). The weight of evidence favours a two-factor structure over the historical single sum score, but solutions vary by sample and language.
Sub-grades (evidence differs by subgroup):
- {"subgroup": "one-factor (historical sum-score assumption)", "grade": "Low", "note": "generally not supported by CFA in representative samples"}
- {"subgroup": "two correlated factors", "grade": "Moderate", "note": "most frequently replicated solution (subjective work ability vs health-related)"}
Convergent and discriminant validity Moderatewell-establishedevidence form: canonical
direct working individuals, aeronautical workers, construction workers and healthcare workers (flag basis: working individuals completing the Spanish-language version; Spanish aeronautical workers; Iranian construction workers; Iranian healthcare workers)
The WAI correlates positively with self-rated general health and health-related quality of life, consistent with its construct. In working individuals completing the Spanish-language version it correlated significantly with the SF-36 v2 (Bascour-Sandoval 2020), and in Spanish aeronautical workers it was highly correlated with self-assessed health status (Gonzalez-Dominguez 2024). Among Iranian construction workers the WAI explained about 46 per cent of the variance in WHOQOL-BREF quality of life, very close to the single-item score (Mokarami 2021). Convergence with the SF-36 has also been used as evidence of criterion/convergent validity in Iranian healthcare workers (Abdolalizadeh 2012). Discriminant (known-groups) validity is consistently demonstrated: WAI separates groups differing in individual characteristics and working conditions (Martinez 2025) and groups with different levels of sick leave (Abdolalizadeh 2012).
Criterion validity: reference standard Absent (the property does not apply to this construct)untestedevidence form: canonical
absence type: category-error the property does not apply to this construct
There is no diagnostic gold standard for work ability, so reference-standard criterion validity is assessed chiefly against established health measures. The WAI correlates moderately to strongly with the SF-36 and WHOQOL-BREF (Abdolalizadeh 2012; Mokarami 2021; Bascour-Sandoval 2020), and its own dimensions include physician-diagnosed disease counts. However, these are health-status comparators rather than an independent diagnostic reference standard, so this criterion is better regarded as convergent evidence; a true reference-standard anchor for work ability does not exist.
Criterion validity: organisational Highwell-establishedevidence form: canonical
direct construction workers, municipal employees, office workers, employees and young employees; also a general-population sample (flag basis: male construction workers; Finnish municipal employees; Dutch office workers; employees; Swedish general-population sample)
This is the WAI's strongest evidential domain: it prospectively predicts work-relevant outcomes in large occupational cohorts. Among 11,537 male construction workers the full WAI discriminated future disability pension well (AUC 0.78, 95% CI 0.75 to 0.80) and was adequately calibrated (Roelen 2014). In 5251 Finnish municipal employees the hazard ratio for disability pension was 5.0 (95% CI 4.4 to 5.6) for poor versus good/excellent WAI (Jaaskelainen 2016). In a Swedish general-population sample the full WAI predicted long-term (90-day) sickness absence over four years with AUC 0.79 (95% CI 0.76 to 0.82), outperforming its individual items (Lundin 2017). Among 1331 Dutch office workers each one-point lower WAI raised the odds of 15 or more sick days (OR 1.27, 95% CI 1.21 to 1.33; AUC 0.77 for 15+ versus 0 days) (Reeuwijk 2015), and in 3660 employees WAI was inversely associated with frequent (OR 0.85), long-term (OR 0.79) and combined (OR 0.74) sickness absence (Notenbomer 2015). Higher WAI was protective against work nonparticipation (long-term sickness absence, early retirement, unemployment) in a representative German cohort (n=2426) (Conway 2023), two WAI items on physical and mental work ability predicted long-term sickness absence across a ten-year follow-up (Palmlof 2019), predicted application for disability pension after vocational rehabilitation (Bethge 2013), and was associated with sickness absence in young employees (Kujala 2006) and with disability more broadly (Alavinia 2009). One caveat: because a WAI dimension counts recent sickness absence days, prediction of absence outcomes is partly non-independent of the predictor. Further sample sizes and statistics: the Swedish AUC came from 1786 employed individuals with 313 incident cases within a survey of n = 6637 (Lundin 2017); the rehabilitation cohort was N = 294 chronic back pain patients, with AUC 0.80 (95% CI 0.62 to 0.97) and adjusted odds of 15.6 for disability pension application at a WAI of 20 or below (Bethge 2013); 850 construction workers aged 40 or over gave hazard ratios for disability of 8 for moderate and 32 for poor work ability (Alavinia 2009); 3725 employees aged 31 gave OR 3.6 for men and 6.2 for women for long-term sickness absence with a low index (Kujala 2006); the WAI itself had OR 0.57 (95% CI 0.52 to 0.63) for disability pension in the construction cohort (Roelen 2014); and the ten-year Swedish study reports no sample size but a 6-fold risk in the oldest age group (Palmlof 2019).
High precondition (rubric 1.6): the cited studies that meet the High precondition, each with a sample size and a statistic of this property; on this population-sensitive property at least one is working-adults or general.
| Study | Sample | Statistic | Population | DOI |
|---|---|---|---|---|
| Bethge 2013 | 294 (168 women; mean age 49.9) | AUC 0.80 (95% CI 0.62 to 0.97) for disability pension application at 3 months; WAI 20 or below: sensitivity 72.7%, specificity 82.2%; adjusted OR 15.6 (95% CI 3.6 to 68.2) for pension application, 4.9 for unemployment, 6 for long-term sick leave | other | 10.1016/j.apmr.2013.05.003 |
| Alavinia 2009 | 850 | Hazard ratios for disability pension 8 (moderate work ability) and 32 (poor work ability); average follow-up 23 months | working-adults | 10.1093/occmed/kqn148 |
| Notenbomer 2015 | 3660 of 6682 invited (55%) | OR 0.85 (95% CI 0.82 to 0.88) frequent, 0.79 (0.75 to 0.82) long-term, 0.74 (0.71 to 0.77) combined sickness absence per WAI point | working-adults | 10.1093/occmed/kqv052 |
| Lundin 2017 | 6637 questionnaire respondents (53% response); 1786 employed with 313 incident LTSA cases | AUC 0.79 (95% CI 0.76 to 0.82) for LTSA of 90 or more days over four years; three items exceeded AUC 0.70 | working-adults | 10.1177/1403494817702759 |
| Reeuwijk 2015 | 1,331 | OR 1.27 (95% CI 1.21 to 1.33) per point lower WAI for 15 or more vs 0 sick days; AUC 0.77 (15 or more vs 0), 0.69 (vs 1 to 5); ORC 0.65; at WAI 27 or below sensitivity 7.5%, specificity 99.6%, PPV 82% | working-adults | 10.1371/journal.pone.0126969 |
| Roelen 2014 | 11,537 (336 reported disability pension) | WAI OR 0.57 (95% CI 0.52 to 0.63) for disability pension; AUC 0.78 (95% CI 0.75 to 0.80); calibration adequate (H-L P = 0.41) | working-adults | 10.5271/sjweh.3428 |
| Jaaskelainen 2016 | 5251 (2057 granted disability pension) | HR 2.0 (95% CI 1.8 to 2.2) moderate and 5.0 (95% CI 4.4 to 5.6) poor vs good/excellent WAI; AUC 0.66 at cut-off 27 (sensitivity 49.2%, specificity 82.9%) and 0.64 at cut-off 36 in first four years | working-adults | 10.5271/sjweh.3598 |
| Kujala 2006 | 3725 (518 with a low index, of whom 90 had long-term absence) | Low WAI (under 37) vs excellent (over 44): OR 3.6 (95% CI 1.6 to 7.9) men, 6.2 (95% CI 2.9 to 13.5) women for certified absence over 9 days; PPV 17.4%, NPV 93.1% | working-adults | 10.5271/sjweh.979 |
Internal consistency Moderatewell-establishedevidence form: canonical
direct healthcare workers and nurses (flag basis: Iranian healthcare workers; Croatian nurses; Brazilian nurses)
Cronbach's alpha for the total WAI typically falls in the 0.7 to 0.8 range: 0.79 in Iranian healthcare workers (Abdolalizadeh 2012), 0.71 in Croatian nurses (Smrekar 2020), and 0.787 (McDonald's omega 0.819) in 3051 Brazilian nurses (Martinez 2025). Values are acceptable but modest, which is expected because the WAI is a heterogeneous composite (partly a formative index of distinct health and work-demand indicators) rather than a homogeneous reflective scale, so alpha is of limited interpretive value for this instrument.
Test-retest reliability Moderatewell-establishedevidence form: canonical
direct nurses/healthcare workers, petrochemical and car-manufacturing workers and construction workers (flag basis: Iranian nurses/healthcare workers aged 40+; petrochemical and car-manufacturing workers; elderly Dutch construction workers aged 40+)
| Coefficient | Type | Interval | Sample | Population | Evidence form |
|---|---|---|---|---|---|
| 0.92 | ICC | repeat administration (interval not specified in report) | 60 | Iranian nurses/healthcare workers aged 40+ | canonical |
| all seven dimensions >0.70 | ICC | test-retest (interval not specified in report) | subset of 750 | Iranian petrochemical and car-manufacturing workers | canonical |
| 66% agreement on four-category classification; 95% of individual score differences within 6.86 points; no group-level mean change (40.4 vs 39.9) | other (agreement / limits of change) | 4 weeks | 97 | elderly Dutch construction workers aged 40+ | canonical |
Full-scale WAI test-retest reliability is adequate. A four-week study in elderly construction workers found stable group means and 66 per cent exact category agreement without reporting an ICC (de Zwart 2002); Iranian validations report ICCs of 0.92 for the total score (Abdolalizadeh 2012) and above 0.70 for each dimension (Adel 2019). Retest reliability of the single first item (Work Ability Score) is treated separately and is more variable; see the WAS record.
Measurement invariance Absent (searched; none found in the sweep to date)untestedevidence form: canonical
absence type: population-general searched; none found in the sweep to date
Formal measurement-invariance testing (configural, metric, scalar) across sex, age, occupation, language or time was not located for the WAI in in the latest review pass. Several studies report factor structures in different countries and note mean score differences by age (younger workers scoring higher), but cross-group score differences are not evidence of measurement invariance, and the varying factor solutions across samples (Martus 2010; Freyer 2018; Mateo Rodriguez 2021) suggest invariance cannot be assumed. This is a genuine gap.
Responsiveness and MIC Absent (searched; none found in the sweep to date)untestedevidence form: canonical
absence type: population-general searched; none found in the sweep to date
Responsiveness and minimal important change for the full 7-item WAI were not established in the retrieved literature; longitudinal WAI studies use it as a predictor rather than an outcome, and no anchor-based MIC for the total index was located. Responsiveness and MIC evidence exists for the single-item Work Ability Score (in clinical rehabilitation samples) and is reported in the WAS record.
Populations, languages and norms
The WAI has been translated and psychometrically examined in many languages and settings, including Finnish (origin), Dutch, German, Spanish, Croatian, Brazilian-Portuguese, Persian, Thai and Turkish. German normative reference tables (by sex and age band 31 to 40, 41 to 50, 51 to 60) are published by the national steward BAuA. Most validation is in ageing occupational cohorts, nurses and industrial workers. No UK-specific norms were located in the latest review pass.
Criticisms and controversies
The main controversy is dimensionality: the historical practice of summing all items into a single 7 to 49 score assumes unidimensionality that confirmatory analyses in representative samples reject in favour of a two-factor structure, prompting the German steward to develop a weighted two-factor calculation. Because the index mixes reflective and formative indicators (self-rated ability, diagnosed disease counts, sickness absence days), internal consistency is only a weak indicator of quality and the composite is conceptually blurred, motivating proposals to use short uni-dimensional components instead. Predictive validity for sickness absence is partly circular because a WAI dimension counts recent absence. Finally, the licence position is easily mis-stated and could not be confirmed against a primary steward page in the latest review pass (both FIOH and BAuA blocked automated retrieval): the questionnaire is commonly described in the literature as freely usable for research, but 'WAI' is trademarked and FIOH sells an official manual, so no open-content licence should be assumed pending direct confirmation of current steward terms.
References (22)
- de Zwart B, Frings-Dresen M, van Duivenbooden J (2002). Test-retest reliability of the Work Ability Index questionnaire. https://doi.org/10.1093/occmed/52.4.177
- Kujala V, Tammelin T, Remes J, Vammavaara E, Ek E, Laitinen J (2006). Work ability index of young employees and their sickness absence during the following year. https://doi.org/10.5271/sjweh.979
- Alavinia S, de Boer A, van Duivenbooden J, Frings-Dresen M, Burdorf A (2009). Determinants of work ability and its predictive value for disability. https://doi.org/10.1093/occmed/kqn148
- Martus P, Jakob O, Rose U, Seibt R, Freude G (2010). A comparative analysis of the Work Ability Index. https://doi.org/10.1093/occmed/kqq093
- Abdolalizadeh M, Arastoo A, Ghsemzadeh R, Montazeri A, Ahmadi K, Azizi A (2012). The psychometric properties of an Iranian translation of the Work Ability Index (WAI) questionnaire. https://doi.org/10.1007/s10926-012-9355-3
- Bethge M, Gutenbrunner C, Neuderth S (2013). Work Ability Index predicts application for disability pension after work-related medical rehabilitation for chronic back pain. https://doi.org/10.1016/j.apmr.2013.05.003
- Roelen C, van Rhenen W, Groothoff J, van der Klink J, Twisk J, Heymans M (2014). Work ability as prognostic risk marker of disability pension: single-item work ability score versus multi-item work ability index. https://doi.org/10.5271/sjweh.3428
- Notenbomer A, Groothoff J, van Rhenen W, Roelen C (2015). Associations of work ability with frequent and long-term sickness absence. https://doi.org/10.1093/occmed/kqv052
- Reeuwijk K, Robroek S, Niessen M, Kraaijenhagen R, Vergouwe Y, Burdorf A (2015). The Prognostic Value of the Work Ability Index for Sickness Absence among Office Workers. https://doi.org/10.1371/journal.pone.0126969
- Jääskeläinen A, Kausto J, Seitsamo J, Ojajärvi A, Nygård C, Arjas E, Leino-Arjas P (2016). Work ability index and perceived work ability as predictors of disability pension: a prospective study among Finnish municipal employees. https://doi.org/10.5271/sjweh.3598
- Lundin A, Leijon O, Vaez M, Hallgren M, Torgén M (2017). Predictive validity of the Work Ability Index and its individual items in the general population. https://doi.org/10.1177/1403494817702759
- Freyer M, Formazin M, Rose U (2018). Factorial Validity of the Work Ability Index Among Employees in Germany. https://doi.org/10.1007/s10926-018-9803-9
- Adel M, Akbar R, Ehsan G (2019). Validity and reliability of work ability index (WAI) questionnaire among Iranian workers; a study in petrochemical and car manufacturing industries. https://doi.org/10.1002/1348-9585.12028
- Palmlöf L, Skillgate E, Talbäck M, Josephson M, Vingård E, Holm L (2019). Poor work ability increases sickness absence over 10 years. https://doi.org/10.1093/occmed/kqz083
- Bascour-Sandoval C, Soto-Rodríguez F, Muñoz-Poblete C, Marzuca-Nassr G (2020). Psychometric Properties of the Spanish Version of the Work Ability Index in Working Individuals. https://doi.org/10.1007/s10926-019-09871-0
- Smrekar M, Franko A, Petrak O, Zaletel-Kragelj L (2020). Validation of the Croatian Version of Work Ability Index (WAI) in Population of Nurses on Transformed Item-Specific Scores. https://doi.org/10.2478/sjph-2020-0008
- Mokarami H, Cousins R, Kalteh H (2021). Comparison of the work ability index and the work ability score for predicting health-related quality of life. https://doi.org/10.1007/s00420-021-01740-9
- Mateo Rodríguez I, Knox E, Oliver Hernández C, Daponte Codina A, The esTAR Group (2021). Psychometric Properties of the Work Ability Index in Health Centre Workers in Spain. https://doi.org/10.3390/ijerph182412988
- Conway P, Burr H, Kersten N, Rose U (2023). Work Ability and Work Nonparticipation: A Prospective Study of 2426 Participants in Germany. https://doi.org/10.1097/JOM.0000000000003032
- Pucci R, da Silva A, Padula R (2024). Factorial analysis of the Brazilian-Portuguese version of the Work Ability Index, reproducibility and validity of the single item and the short version for online application. https://doi.org/10.1016/j.bjpt.2024.101060
- González-Domínguez M, Fernández-García E, Paloma-Castro O, González-López R, Rivas Pérez M, López-Molina L, García-Jiménez J, Romero-Sánchez J (2024). Work Ability Index: Psychometric Testing in Aeronautical Industry Workers. https://doi.org/10.1016/j.shaw.2023.12.001
- Martinez M, Latorre M, Fischer F (2025). Validity and reliability of the Brazilian version of the Work Ability Index - WAI: a re-evaluation. https://doi.org/10.1590/1413-81232025309.07832024
Record notes
Overall confidence: organisational criterion validity is High and well-established (large prospective occupational cohorts predicting disability pension and sickness absence); structural validity is Moderate but contested (two-factor preferred over the historical sum score); internal consistency and test-retest are Moderate; measurement invariance and full-scale responsiveness/MIC are genuine gaps (Absent). Under rubric 1.0 every grade was flagged indirect because no UK validation or norms were located; under rubric 1.1 the occupational-cohort evidence is direct and the absence of UK norms is a fact in the populations cell (correction C-0004). Schema v0.2 handled this instrument well; the one hard case was internal consistency, which is a partly-formative composite where alpha is reported in the literature but is of limited interpretive value, noted in the findings and status rather than forced into a misleading grade. Licence could not be verified against a primary steward page in the latest review pass because FIOH (ttl.fi) and BAuA (baua.de) returned server-side 403 blocks and the reachable WAI-Netzwerk portal does not state questionnaire terms; per rule 7 the licence is recorded as not verified in the latest review pass rather than asserted from literature.