Advances in healthcare, and effective public health campaigns to disseminate cardiopulmonary resuscitation (CPR) and portable defibrillators, have doubled the survival rate for cardiac arrest (CA) in the last decade (from 16% to 33%). Patients whose hearts stop beating for many minutes are now resuscitated, kept in a medically induced coma, and have their bodies cooled to 89°- 93°F (to reduce brain damage), resulting in many more CA survivors returning to full lives. However, CA patients remain at markedly elevated risk for major adverse cardiovascular events (MACE) and all-cause mortality (ACM), and many report poor health-related quality of life (HRQoL) in the year after CA--despite returning to independence (and often to work) with cognition intact. We propose that cardiac anxiety (i.e., cardiac specific-fear, avoidance behavior, and excessive cardiac symptom monitoring) may partly explain MACE/ACM risk and poor HRQOL. It is highly prevalent in CA patients and has been shown in non-CA cardiovascular disease (CVD) patients to be associated with higher rates of CVD- related distress, avoidance of physical activity, patient-reported disability, and poor perceived health. We will build a prospective cohort of CA survivors, comprehensively assess cardiac anxiety and other psychological and behavioral consequences of CA in the first year of survivorship, and estimate the association of cardiac anxiety, physical activity, and sleep with subsequent MACE/ACM and HRQoL. We will enroll a cohort of 246 CA inpatients, assess psychological and HRQoL measures at enrollment, and by telephone at 1, 6, and 12 months. We will assess physical activity and sleep by actigraphy for 2-weeks after discharge and again for 2 weeks before a 6-month follow-up and follow participants for 12 months to MACE/ACM. This would be the first major prospective cohort study of CA survivorship, and the first to objectively assess health behaviors. For our Aim 1, we will estimate the prospective association of cardiac anxiety at CA discharge with subsequent risk for CVD/mortality after adjusting for general psychological distress and other significant clinical covariates and test its independent association with HRQoL. Our second aim is to test whether cardiac anxiety after CA is associated with low physical activity and/or short sleep shortly after discharge. Physical activity (PA) and sleep are implicated in CVD risk and chronic disease progression, but no study has assessed PA or sleep in CA survivors. Our pilot data suggest that survivors of other acute cardiac events report avoiding physical activity because it causes threatening physiological signals (i.e., increased heart rate, shortness of breath), and poor sleep due to cardiac anxiety. Lastly, our third aim is to quantify the extent to which low PA and/or short sleep after CA predict MACE/ACM, and mediate the association between cardiac anxiety and 12-month MACE/ACM post-discharge for CA. By identifying malleable intervention...