What do we know about the Epworth Sleepiness Scale in women? A review of the evidence.

The Epworth sleepiness scale (ESS) is the most widely used subjective measure of excessive daytime sleepiness (EDS), yet its psychometric validity across sexes has not been systematically evaluated. This narrative review examined published studies assessing sex differences in the psychometric properties of the ESS and evaluated whether sufficient evidence supports its validity for use in women. Of 288 screened articles, 56 evaluated ESS psychometrics and 10 assessed sex differences. No study had as its primary aim the evaluation of sex-based measurement validity. Most investigations relied on univariate comparisons or internal consistency estimates and reported no significant sex differences in ESS total scores. A few studies used sound methods to identify sex-related differences in individual items, optimal cut-scores, score stability, and associations with objective sleep apnea indices. However, no studies formally tested measurement invariance between sexes for the construct of sleepiness. Methods varied substantially across studies, limiting comparability. Although the ESS demonstrates overall reliability and unidimensionality, evidence supporting sex equivalence is limited. Emerging item-level differences suggest potential measurement non-equivalence that may obscure sex-specific symptom presentation, particularly in women with obstructive sleep apnea. Rigorous sex-specific psychometric evaluation is needed to ensure accurate assessment and equitable clinical decision-making.