Recent research highlights the potential link between the maternal X chromosome and accelerated brain ageing. This connection could explain heightened risks for conditions such as Alzheimer's disease. The study focuses on the biological role of the X chromosome, passed down by mothers, which carries a significant genetic load. Variations or mutations in this chromosome may profoundly affect brain health, especially since one X chromosome in females is randomly inactivated in each cell. Although women generally live longer and have lower overall dementia rates than men, Alzheimer's disease affects more women, though they often survive longer with the condition. Researchers theorized that differences in sex chromosomes (X and Y) might account for these disparities. Dena Dubal, the study’s senior author, emphasized that skewing of X chromosomes is common. Some individuals naturally carry higher proportions of maternal X chromosomes, potentially leading to varied impacts on cognitive health. To investigate, researchers conducted experiments on female lab mice. In some mice, the paternal X chromosome was silenced, leaving only the maternal X active. Initially, the “Mom-X” mice performed cognitively on par with others, but as they aged, their cognitive decline steepened. Examination of their hippocampus—a key area for memory and learning—showed advanced biological ageing. The findings suggest that maternal genetic contributions to the X chromosome could play a critical role in brain ageing and age-related cognitive disorders. The study opens doors for further exploration into how these genetic factors might influence health over a lifetime.