Individual differences in sleep-wake cycles give rise to "morningness-eveningness." The assessment of morningness-eveningness is essential for understanding these preferences, and the Reduced Morningness-Eveningness Questionnaire (rMEQ) has been developed for this purpose. The purpose of this study was to examine the Arabic rMEQ's psychometric properties in terms of validity, reliability and measurement invariance across sex groups. A population-based sample of 330 Arabic-speaking participants from Lebanon, comprising 67.3% females with a mean age of 21.75 ± 2.43 years (range: 18-33), were recruited for this study. The participants were asked to fill out an online questionnaire consisting of the Arabic versions of the rMEQ, Pittsburgh Sleep Quality Index (PSQI), and the Lebanese Anxiety Scale (LAS). Confirmatory factor analysis (CFA) indicated a modest fit for the one-factor model of the rMEQ. Internal reliability was good, with ω = .75 and α = .70. Additionally, cross-sex invariance analysis showed support for configural, metric, and scalar invariance, with no significant differences in rMEQ scores between males and females. Concurrent validity revealed significant moderate correlations between higher rMEQ scores and lower depression, better sleep quality, and lower anxiety. The Arabic version of the rMEQ demonstrated adequate psychometric properties in a Lebanese adult population. The CFA results support a one-factor model of the Arabic rMEQ, similarly as in the case of other language versions. Overall, the Arabic rMEQ appears to be a valid and reliable tool for evaluating morningness-eveningness in Arabic-speaking adults, with potential applications in cross-cultural chronotype studies.
