PROJECT SUMMARY/ABSTRACT Low-income older adults (LIOA) are a population at higher risk to develop Alzheimer's disease and related dementias (ADRD) and sleep disturbances. Although empirical research suggests that physical activity interventions benefit cognition and sleep in older adults in general, the possible benefit of physical activity is understudied in LIOA. The available evidence in LIOA suggests that LIOA experience unique barriers to physical activity, more prevalent physical inactivity and sedentary behaviors. Since physical inactivity and sedentary behaviors are independent risk factors that have synergistic harmful effects for cognitive function and sleep, it is crucial to address them simultaneously to promote cognitive and sleep health in LIOA. The growing wearable device and mobile Health (mHealth) provide an innovative approach to deliver individually tailored physical activity interventions at home with flexible schedules to overcome barriers to physical activity in LIOA. In addition, limited research has examined if physical activity interventions impact the individual’s Amyloid/Tau/ Neurodegeneration (ATN) Alzheimer's disease biological state and whether physical activity may promote cognition through impacting sleep and AD pathology. This randomized controlled trial is designed to examine the immediate and sustaining efficacy of an mHealth-facilitated Physical Activity Toward Health (mPATH) intervention on cognitive function and sleep in LIOA. mPATH is a personalized physical activity intervention that includes personalized physical activity plans and training sessions, exercise at home by following personalized exercise videos, and biweekly phone coaching over 24 weeks, supported by wearable devices-enabled mHealth strategies. mHealth strategies and exercise videos will be used to support participant’s physical activity during 6-12months. In the proposed study, we will randomize 176 community dwelling LIOA with insomnia symptoms and without dementia to the mPATH or control group on a 1:1 ratio. Randomization will be stratified by age, sex, and cognitive status. Specifically, we will (1) test the immediate (6- month) and sustaining (12-month) effects of mPATH on cognitive function among LIOA, compared to control; (2) test the immediate (6-month) and sustaining (12-month) effects of mPATH on sleep, compared to control; and (3) explore the effect of mPATH on ATN biomarkers and potential mediating roles of sleep and ATN biomarkers in mPATH’s effect on episodic memory.