Menstrual cycle phase influences cognitive performance in women and modulates sex differences: A combined longitudinal and cross-sectional study of cognitive function in young adults

Sex differences in cognitive performance have been widely studied, yet the role of sex hormones and their fluctuations across the menstrual cycle remains unclear. This study investigated cognitive performance differences between men and women, accounting for menstrual cycle phases, and examined associations between sex hormone levels and cognitive function. Seventy-one healthy young adults (42 women, 29 men) participated in the study. Women were tested twice, once during their menstrual (low oestradiol) phase and once during their pre-ovulatory (high oestradiol) phase. Men underwent a single assessment. Cognitive performance was evaluated using standardised tests that measured attention, processing speed, working memory, and visuospatial abilities. Blood samples were collected to measure oestradiol, progesterone, and testosterone levels. Women showed enhanced performance during the pre-ovulatory phase compared to the menstrual phase in working memory capacity (digit span forward: p = 0.04; backward max: p = 0.02) and attention switching (Trail making test B ( TMT B): p = 0.01). Sex differences in processing speed were observed only when men were compared to women in their menstrual phase (TMT A: p = 0.03; Stroop B: p = 0.04). These differences disappeared during the women's pre-ovulatory phase. While testosterone showed no significant correlations with cognitive measures, oestradiol and progesterone demonstrated distinct relationships. Positive correlations were shown with cognitive performance in men, and there were complex bidirectional relationships in women, but only during the menstrual phase. These findings suggest that cognitive differences between the sexes are modulated by hormonal status, with higher oestradiol levels potentially enhancing women's cognitive performance. Further research is needed to elucidate the complex mechanisms underlying these hormone-dependent cognitive changes. This study highlights the importance of considering the phase of the menstrual cycle when investigating sex differences in cognitive function.