Cross-cultural adaptation and assessment of psychometric properties of the Polish version of the Hairdex Life Quality Questionnaire (Hairdex-PL)

BACKGROUND: Hair and scalp disorders substantially impair health-related quality of life (HRQoL), yet no validated Polish-language disease-specific instrument is currently available to assess this burden. OBJECTIVES: This study aimed to translate, cross-culturally adapt, and assess the structural validity and internal consistency of the Polish version of the Hairdex questionnaire (Hairdex-PL). MATERIAL AND METHODS: The original 48-item German Hairdex questionnaire was translated and culturally adapted according to the Beaton guidelines. Psychometric evaluation was performed in 245 adults with hair loss or scalp disorders recruited through an online survey. Structural validity was assessed using confirmatory factor analysis (CFA), followed by exploratory factor analysis (EFA) when the predefined model demonstrated inadequate fit. Internal consistency was assessed using Cronbach's α and McDonald's ω. RESULTS: A total of 245 participants (55.9% women; 44.1% men; mean age 35.8 ±9.7 years) were included in the final analysis. Confirmatory factor analysis did not confirm the original 5-factor structure (root mean square error of approximation (RMSEA) = 0.234; comparative fit index (CFI) = 0.744; Tucker-Lewis index (TLI) = 0.749; standardized root mean square residual (SRMR) = 0.192). Exploratory factor analysis retained a single factor explaining 38.2% of the total variance. The greatest impairment in HRQoL was observed in the Self-confidence and Emotions domains, corresponding to the greatest impairment in the same items in the original Hairdex, whereas Functioning and Symptoms were the least affected. Stigmatization had an intermediate mean score. Internal consistency was high (Cronbach's α = 0.960; McDonald's ω = 0.963). CONCLUSIONS: Hairdex-PL showed high internal consistency and provided preliminary psychometric evidence supporting its use to assess disease-specific HRQoL in Polish-speaking individuals with hair and scalp disorders. Although confirmatory factor analysis did not support the original 5-factor structure, exploratory factor analysis identified a single factor in the present sample; this exploratory finding requires confirmation in an independent population. This study provides new evidence regarding its underlying measurement structure and supports further evaluation of the instrument in clinical and research settings.