PROJECT SUMMARY/ABSTRACT Sleep is normally a period of biological rest and recuperation for the cardiovascular system. Inadequate or low- quality sleep is known to increase the risk of cardiovascular disease (CVD). Increasing evidence also suggests that cardiac aging is an important hallmark of CVD. Traditional sleep assessment is based on questionaries that are known to suffer from limited resolution and existing biases. In addition, sleep quality is typically measured at a single examination, which limits its capability to assess the impact of changes in sleep patterns on cardiac health. Recent advances in digital technologies provide a promising solution to assess the impact of sleep pathology on cardiac health longitudinally. We hypothesize that impaired sleep quality and sleep apnea accelerate cardiac electrophysiological aging and increase the risk of cardiovascular disease. We will leverage a rare longitudinal collection of objective sleep measures and cardiovascular health in the Korean Genome and Epidemiology Study (KoGES). Our study will include ~2800 participants who have 3 cycles of overnight polysomnography starting in 2011 and 4th cycle to be completed by 2025. Two specific aims will be pursued. In Aim 1, we will assess the association of sleep apnea on aging cross-sectionally and longitudinally over 12 years. In Aim 2, we will determine if specific sleep and sleep apnea endotypes are associated with accelerated cardiac aging. This investigation will provide critical knowledge to better understand the impact of sleep on cardiac aging and cardiac health. Our long-term goal is to use sleep-targeted treatment as a way to preserve cardiac function, preventing the inevitable deterioration with aging.