Psychometric properties of the health literacy instrument for Iranian community-dwelling older adults (HELIO)

Health literacy (HL) plays a key role in enabling older adults to effectively manage their health conditions and make informed health decisions. Despite the availability of the Health Literacy Instrument for Adults (HELIA) in Iran, its psychometric properties have never been evaluated in older adults—a population with distinct cognitive and educational characteristics that may affect the validity of measurement tools. To address this gap, we adapted the HELIA into the Health Literacy Instrument for Older Adults (HELIO) and evaluated its psychometric properties. This study, therefore, provides the first validated instrument specifically designed for health literacy assessment in Iranian community-dwelling older adults. This psychometric study was conducted among 495 Iranian older adults selected through a two-stage cluster sampling method. The adapted instrument, HELIO underwent psychometric evaluation including face, content, and construct validity, and reliability and stability assessments using Cronbach’s alpha and intra-class correlation coefficient (ICC) tests. Applying the Principal Component Analysis (PCA) ( n = 247 samples) and Confirmatory Factor Analysis (CFA) ( n = 248 samples), we examined the construct validity of the HELIO. Data were analyzed using SPSS version 25 and STATA version 15. The mean age of participants was 64.87 ± 5.49 years, and 53.8% were women. Based on content validity assessment, five items were removed from the original instrument. The PCA and CFA confirmed the original five-factor structure with 28 items, which altogether accounted for 35.9% of the variance. The KMO value was 0.71, and Bartlett’s test was significant (P-value < 0.001). In the CFA, the fit indices of Comparative Fit Index (CFI) = 0.99, Tucker-Lewis Index (TLI) = 0.99, GFI = 0.91, AGFI = 0.89, and Root Mean Square Error of Approximation (RMSEA) = 0.000 (90% CI: 0.000 to 0.019) approved a strong fit to the data. Although the total scale demonstrated excellent internal consistency (Cronbach’s α = 0.94; McDonald’s ω = 0.95), not all subscales meet the criterion for satisfactory reliability. The HELIO demonstrated acceptable validity and reliability, providing a promising tool for health literacy assessment among Persian-speaking older adults, though further cross-cultural validation is needed.