Psychometric Properties of the Adjustment to Aging Scale (Atas) in Iranian Older Adults

<b>Background/Objectives:</b> Adjustment to aging is a key indicator of positive aging and psychological maturity, influenced by cultural and social contexts. This study aimed to translate and evaluate the psychometric properties of the Adjustment to Aging Scale (AtAS) among Iranian older adults. <b>Material and methods:</b> This cross-sectional study was conducted in Tehran, 2024. Following translation and cross-cultural adaptation, face validity, content validity, and reliability of the questionnaire were assessed. The WHO-5 well-being index was used to assess concurrent validity. A total of 328 older adults aged 60 years and above completed the study instruments. Data were analyzed using Confirmatory Factor Analysis (CFA), Cronbach's alpha, Pearson correlation, independent t-tests, and ANOVA via SPSS version 22 and AMOS 24. The significance level was set at <i>p</i> ≤ 0.05. <b>Results:</b> The mean (SD) age of the participants was 69.42 (6.8) years. Face and content validity were confirmed by fourteen experts (CVI = 0.94). CFA supported the five-factor structure of the questionnaire (χ²/df = 2.06, GFI = 0.90, PCLOSE = 0.07, RMSEA = 0.05), indicating a good model fit. The total questionnaire showed acceptable internal consistency (Cronbach's alpha = 0.80) and excellent test-retest reliability (ICC = 0.98). Pearson's correlation revealed a significant positive relationship between the WHO-5 Well-Being Index and AtAS scores (r = 0.56, <i>p</i> < 0.05), supporting criterion validity. <b>Conclusions:</b> The Persian AtAS showed strong psychometric properties, supporting its use in both research and clinical settings, although further studies are recommended to strengthen evidence for its clinical application.