This protocol is a retrospective study using the observational data of the the Prostate, Lung, Colorectal, and Ovarian (PLCO) screening trial with over 150,000 participants aged 55-74 years to conduct a target trial emulation to examine the association between self-reported exercise and all cause and cause-specific mortality in apparently healthy, middle-aged and older adults. The PLCO includes assessments of participants' exercise level at two timepoints: at randomization into the PLCO trial (Q0) and 5-7 years after randomization into the PLCO (Q1).

• 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.](streamdown:incomplete-link)

Adults enrolled into the PLCO screening trial