Changes of individual BrainAGE during the course of the menstrual cycle.

Brain morphology varies during the course of the menstrual cycle, with increases in individual gray matter volume at the time of ovulation. This study implemented our previously presented BrainAGE framework to analyze short-term neuroanatomical changes in healthy young women due to hormonal changes during the menstrual cycle. The BrainAGE approach determines the complex multidimensional aging pattern within the whole brain by applying established kernel regression methods to anatomical brain MRIs. The "Brain Age Gap Estimation" (i.e., BrainAGE) score is then calculated as the difference between chronological age and estimated brain age. Eight women (21-31 years) completed three to four MRI scans during their menstrual cycle (i.e., at (t1) menses, (t2) time of ovulation, (t3) midluteal phase, (t4) next menses). Serum levels of estradiol and progesterone were evaluated at each scanning session. Individual BrainAGE scores significantly differed during the course of the menstrual cycle (p<0.05), with a significant decrease of -1.3 years at ovulation (p<0.05). Moreover, higher estradiol levels significantly correlated with lower BrainAGE scores (r=-0.42, p<0.05). In future, the BrainAGE approach may serve as a sensitive as well as easily implementable tool to further explore the short-term and maybe long-term effects of hormones on brain plasticity and its modulating effects in lifestyle-related diseases and dementia.