Sedentary behavior (spending most of the awake time in sitting/ recumbent posture) and physical inactivity (lack of achieving weekly moderate/ vigorous physical activity goals) are not interchangeable terms but represent distinct domains; one could be physically active and achieve the weekly goal of 150 min/week of MVPA but still spend the rest of the awake hours sedentary. Technological advances have led to the development of accelerometers for objectively measuring the posture, duration and intensity of physical activities. “Pragmatic Evaluation of Events And Benefits of Lipid-lowering in older adults (PREVENTABLE)” Trial is a NIA funded ongoing randomized controlled trial evaluating the effects of a statin on cognitive function and physical disability outcomes in older adults (age ≥ 75 years). The trial is in recruitment phase with a target N of 20,000. Leveraging the resources of the parent study, we propose to recruit 2,500 participants in this ancillary study and objectively measure sedentary, standing and stepping durations and the number of steps/day with a validated accelerometer to examine two distinct questions of public health importance. First, higher levels of moderate/ vigorous physical activities have been associated with lower risk of developing Alzheimer’s disease or related dementias (ADRD). However, physical inactivity and sedentary behavior are distinct domains. Prospective longitudinal studies relating sedentary behavior with the risk of ADRD are lacking. Hence, in the first specific aim, in a longitudinal, prospective analysis, we will examine the hypothesis that longer sedentary duration increases risk of incident mild cognitive impairment (MCI)/ probable ADRD; whereas, trade-off of sedentary duration for stepping duration is associated with lower risk of these outcomes. Second, there are conflicting data on the associations of statins with physical disability/ physical activity. PREVENTABLE is examining the possible role of atorvastatin in preventing disability (but not physical activity). We propose to add objective measures of physical activity. In the second aim, we will examine the hypothesis that decrease in physical disability and preservation of functional ability with randomization to atorvastatin compared to placebo will result in higher physical activity levels and lower sedentary duration. The investigators on this multi-disciplinary team have the experience and expertise to carry out all aspects of the project. The proposed ancillary study will be well integrated into the pragmatic design of the parent trial and place minimal burden on participants and parent study staff. By adding rigorous measures of sedentary behavior and physical activity, this ancillary study will create synergy with the parent trial to enhance scientific yield by addressing an important gap in the parent study. If sedentary behavior is associated with incident MCI/ ADRD in older adults, the results of the current study will aid in the...