Evaluating measurement invariance and diagnostic accuracy of climate anxiety scales in aging populations: a multi-instrument approach

Climate change is increasingly recognized as a psychological stressor, with older adults representing a particularly vulnerable yet understudied group. This study evaluated the psychometric performance of three climate anxiety measures-the Hogge Climate Anxiety Scale (HCAS), Clayton Climate Change Anxiety Scale (CCCA), and Simon Climate Anxiety Scale (SCAS)-among 279 Persian-speaking older adults in Iran. Using a cross-sectional design, we examined structural validity, diagnostic accuracy, measurement invariance, and reliability, employing the GAI-SF as the criterion measure. All three instruments demonstrated acceptable construct validity based on exploratory and confirmatory factor analyses. SCAS showed a stable three-factor structure and excellent internal consistency (ω = 0.97). In classification analyses, SCAS achieved the highest sensitivity (0.89) and overall diagnostic accuracy (DOR = 3.09), whereas CCCA demonstrated slightly higher specificity (0.36). Bland-Altman analysis indicated that HCAS had the lowest measurement bias relative to GAI-SF scores. Measurement invariance testing supported full scalar invariance for SCAS across gender and anxiety subgroups, while HCAS and CCCA achieved only partial invariance. Mokken scale analysis further confirmed strong scalability (H > 0.40) and satisfactory reliability (α > 0.85) across all measures, with CCCA showing the highest Loevinger's H (0.52). Age significantly predicted climate anxiety scores across all three scales (p < 0.001). Overall, SCAS emerged as the most robust and reliable instrument for assessing climate anxiety in Persian-speaking older adults, while HCAS showed the closest agreement with the criterion measure. These findings highlight the importance of culturally adapted, psychometrically sound tools for capturing climate anxiety in aging populations.