Psychometric Properties of the Traditional Chinese Version of the Friendship Scale for Older Adults

Cultural differences, along with various social and political determinants, affect the social isolation experienced by older adults. This study aimed to investigate the factor structure of the Traditional Chinese version of the Friendship Scale (FS-TC) and to assess its psychometric properties in relation to social isolation among Taiwanese older adults. In Phase 1, the scale underwent cultural adaptation and translation before being evaluated for face and content validity by ten older adults and five experts in nursing and geriatric care. Phase 2 involved a cross-sectional study with a convenience sample of 500 older adults from southern Taiwan to establish construct validity, criterion validity, and reliability. Of these participants, 100 were retested 2 weeks later to assess test-retest reliability. The scale-level content validity index was 1.0. A confirmatory factor analysis showed a two-factor structure of the FS-TC, consisting of "connection" and "isolation" factors. The Cronbach's α for the scale was 0.82, while the intraclass correlation coefficient reached 0.96. Convergent validity was demonstrated through significant correlations with the Geriatric Depression Scale, the Social Support Scales, and the Loneliness Scale. The FS-TC showed a sensitivity of 56% and a specificity of 89% for predicting Lubben Social Network Scale-6 measured social isolation. An optimal cut-off score of 14.5 was identified for predicting social isolation in older adults. Overall, the FS-TC was shown to be a reliable and valid measure of social isolation, making it a valuable tool for healthcare providers and researchers assessing the severity of social isolation among Taiwanese older adults.