A SMART Trial of Adaptive Exercises to Optimize Aerobic-Fitness Responses

The purpose of this Phase II, mechanistic Sequential, Multiple Assignment, Randomized Trial (SMART) is to test the effects of 6-month aerobic exercise on aerobic fitness and MRI and plasma biomarkers in community-dwelling older adults with early Alzheimer's disease (AD). The aims are to (I) test the effects of aerobic exercise on aerobic fitness, white matter hyperintensity (WMH) volume, and patient-centered outcomes; (II) identify the best exercise to improve aerobic fitness and reduce non-responses over 6 months; and (III) examines the mechanisms of aerobic exercise's action on memory in older adults with early AD. This trial builds on our previous work showing inter-individual differences in VO2peak responses to moderate-intensity continuous training (MICT); an ability of plasma neurofilament light chain (NfL) to predict cognition; and 6-month MICT maintained memory, reduced WMH, affected plasma p-tau181, and improved physical function, QoL, and caregiver distress. Aerobic exercise is a promising treatment for Alzheimer's disease (AD) and AD-related dementia (ADRD) but has shown mixed effects on cognition, physical function, behavioral and psychological symptoms of dementia (BPSD), quality of life (QoL), and caregiver burden. These findings are likely due to inter-individual differences in aerobic fitness responses, which have long been established in adults using VO2peak and were first reported in AD/ADRD by our team. Most AD/ADRD exercise trials did not measure VO2peak and those that reported large inter-individual differences in VO2peak responses to MICT. Mechanistically, animal studies support aerobic exercise modifying AD's ATN biomarkers (Amyloid-beta [Aβ], Tau, and Neurodegeneration), but human studies are few and have conflicting findings. Hence, precision exercise is critical to improving VO2peak responses with alternative interventions (high-intensity interval training (HIIT) or combined aerobic & resistance exercise (CARE)). Because VO2peak can improve and peak from 3 months of MICT, 3 months is an ideal time to identify MICT non-responders and initiate HIIT or CARE.

Inclusion criteria

Participants:

• Clinical diagnosis of MCI or probable and possible mild AD dementia according to 2011 Alzheimer's association-NIA criteria.
• Community-dwelling, e.g., homes and assisted living
• Age 65 years and older
• Medical clearance from PCP or cardiovascular provider
• Have a qualified study partner
• Agree to the blood draws
• Verified MRI safety

Study Partner:

• Age 18 or older
• Contact with participant ≥ 2 times per week for ≥ 6 months
• Know the participant's memory status and ability to perform activities of daily living
• Consent to participant

Exclusion criteria

Participants

• Resting HR ≤ 50 or ≥ 100 beats/min after 5-minutes of quiet resting
• American College of Sports Medicine contraindications to exercise
• New, unevaluated symptoms or diseases a healthcare provider has not evaluated
• Abnormal cardiac condition uncovered during VO2peak testing
• Enrollment in another intervention that aims at improving cognition
• Moderate to strenuous exercise ≥150 minutes a week in the previous 6 months
• ≥ 2 anti-depression medications, or poorly managed or unstable depression
• Poorly managed or unstable anxiety

Study partners:

• none