Menstrual Cycle Phase Influences Cognitive Performance in Women and Modulates Sex Differences: A Combined Longitudinal and Cross-Sectional Study

Sex hormones' and menstrual cycle's effects on cognitive performance remain unclear. This study examined cognitive differences between women across menstrual cycle phases, sex differences between women and men, and hormone-cognition associations. In total, 71 healthy young adults, aged 20-36 (42 women, 29 men), completed standardised cognitive tests measuring attention, processing speed, working memory, and visuospatial abilities. Women were tested twice: during menstrual (low-oestradiol) and pre-ovulatory (high-oestradiol) phases; men once. Hormone levels (oestradiol, progesterone, testosterone) were measured in blood samples via electrochemiluminescence immunoassay (ECLIA). Two analytical strategies were used: (1) within-subject analysis comparing women between phases, and (2) between-group comparison across three groups-women in menstrual phase, pre-ovulatory phase, and men. Women performed better during pre-ovulatory versus menstrual phase in working memory (Digit span forward: <i>p</i> = 0.04; Digit span backwards max: <i>p</i> = 0.02) and attention switching (Trail Making Test B: <i>p</i> = 0.01). Sex differences in processing speed were observed only during the menstrual phase (Trail Making Test A: <i>p</i> = 0.03; Stroop B: <i>p</i> = 0.04), but not in the pre-ovulatory phase. Positive correlations between oestradiol/progesterone and cognitive performance were found in men, while complex bidirectional relationships emerged in women during the menstrual phase only. Testosterone showed no significant correlations. These findings highlight hormonal status effects on cognitive sex differences.