Dimensionality and cross-language invariance of Pittsburgh Sleep Quality Index among Indian adolescents and adults.

Sleep quality, key to physical and mental health, requires regular assessment in clinical and non-clinical settings. Despite widespread use, the dimensionality of the Pittsburgh Sleep Quality Index (PSQI) is debated, and its Hindi version's factor structure remains unexplored. Our study evaluates the PSQI's dimensionality among Indian adolescents and adults aiming to demonstrate cross-language (Hindi and English) invariance of its factor structure. The PSQI showed satisfactory item reliability, and a best-fitting two-factor model: "sleep efficiency" (comprising sleep duration and habitual sleep efficiency), and "perceived sleep quality" (comprising remaining five PSQI components). This model showed configural invariance across age groups, sexes, and languages. Metric invariance was noted across age groups, but a partial metric non-invariance was observed across languages and sexes as reflected by differences in factor loadings. The second-order factor structure model had an excellent fit indicating the usefulness of aggregate scores of the two factors as a single index of sleep quality. Our findings better support a two-factor structure of sleep quality (both for English and Hindi versions of PSQI) in India. However, further validation in diverse clinical and non-clinical samples is warranted.