The number of young people (aged under 40) being diagnosed with high blood pressure is increasing. Patients with high blood pressure are often overweight or obese and together this substantially increases their risk of cardiovascular and metabolic diseases. At the moment, mechanisms linking obesity and hypertension in young people are not very well understood but abnormalities in a hormone called aldosterone have been associated with both pathologies. There is increasing evidence that the contribution of aldosterone to blood pressure and cardiovascular disease is substantially under recognised. This project proposes to recruit participants in the ALSPAC cohort to perform a short but high-dimensional observational study. I will use a non-invasive biological sampling technique called microdialysis to measure the dynamics of aldosterone in relation to sleep, activity, posture, and internal body rhythms in obese people with and without hypertension, and in a non-obese control comparison group. Access associated phenotype and longitudinal data related to blood pressure and other parameters from ALSPAC will provide enormous extra value.