The age at which girls begin to menstruate, known as menarche, is well-known to be associated with disease risk in later life. For example, girls who begin their periods at an early age are more likely to die prematurely, and to develop poor physical and mental health outcomes in adulthood, including cardiometabolic diseases like type 2 diabetes. While the reasons for this connection are unclear, one possible explanation is that early menarche and cadiometabolic disease risk in adulthood are both associated with patterns of growth and development that have been shaped by natural selection in ancestral populations. Evolutionary theory predicts that in high-risk environments, the body may prioritise survival and early reproduction, and these outcomes may reduce the resources that the body can invest in maintaining health. One important factor in shaping these developmental patterns is the level of maternal nutritional investment in the baby during gestation.
In this project, we seek to better understand how age at menarche is related to cardiometabolic diseases like diabetes by testing for associations between age at menarche and other biological traits that are predicted by the model outlined above. We will do this by exploring the relationship between (i) age at menarche and organ size and function (markers of the metabolic capacity to maintain the body in good health), (ii) early life risk factors for cardiometabolic disease (like birthweight) and age at menarche, and (iii) by examining whether age at menarche acts as an intermediate step in the causal chain linking maternal investment in offspring with the offspring’s later risk of disease. Answering these questions will contribute to our greater understanding of how early life traits are connected to health in adulthood, and potentially help to clarify a mechanism that transmits health inequalities across generations. Knowing about these mechanisms and how they act across the whole human life span is important as we seek to reduce health inequalities in our society. We aim for the analysis to be completed within a year.