Exercise and Mortality in Middle-Aged and Older Adults

* Adults enrolled into the PLCO screening trial. * Among participants reporting low exercise at Q0 (i.e., 0 or less than 1 day/week, with each session \<15 minutes in duration), completion of an exercise survey at Q1 as part of PLCO standard trial procedures no later than 5 years after reporting non-exercising status \[i.e., no exercise) at Q0. * No evidence of any of the following absolute contraindications to exercise: uncontrolled hypertension, symptomatic valvular disease; hypertrophic cardiomyopathy; unstable angina pectoris; primary pulmonary hypertension; heart failure; severe arrhythmia; diagnosed dementia; any form of cancer other than non-melanoma, and severe infectious disease.