The apolipoprotein E epsilon 4 (APOE e4) allele is the most important genetic risk factor for late onset Alzheimer's disease (AD). A recent review by the World Health Organization highlighted the potential protective role of physical activity and exercise against cognitive decline, all-cause dementia, AD, and vascular dementia in healthy individuals. In an 18-month longitudinal observational study, investigators showed that sedentary e4 carriers experience significant declines in episodic memory and hippocampal volume compared to 4 carriers who engaged in moderate PA. Importantly, among 4 non-carriers, no significant longitudinal changes in cognition and brain imaging were observed whether the non-carriers were sedentary or engaged in moderate PA, suggesting that PA has a specific neuroprotective role in delaying the progression of AD in e4 carriers. Based on the results, a pragmatic, randomized controlled trial with blinded clinical and imaging outcomes is proposed to determine the impact of a home based, high intensity exercise intervention in healthy, cognitively intact e4 carriers between the ages of 65 and 80 years. The CYCLE-AD (CYcling to Cease or Limit the Effects of Alzheimer's Disease) trial will recruit otherwise healthy sedentary carriers randomized to one of two groups (n=75 each): 1) an Indoor Cycling (IC) group that participates in high-intensity interval training (HIIT; 60-90% of heart rate reserve) in their home via the commercially available Peloton® cycling system or 2) a Usual and Customary Care (UCC) group, in which participants engage in their habitual level of PA. Investigators hypothesize that an 18-month high-intensity aerobic exercise regimen will slow AD-related disease progression in sedentary elders at genetic risk for AD. Participants in the intervention group will engage in exercise 3x/week (minimum 90 minutes/week) for 18 months. Primary outcome measures, obtained at study entry and at 18 months, will include comprehensive cognitive testing and brain MR imaging to assess disease progression and a comprehensive PA/fitness assessment to measure the degree of change in physical fitness due to high intensity aerobic exercise.
The overall goal of the CYCLE-AD trial is to determine the role of long-term, high intensity exercise in slowing or delaying the onset of cognitive and AD-related brain changes in e4 carriers. Successful translation and demonstration of the effectiveness of a scalable home-based exercise intervention capable of slowing or delaying disease onset will transform AD treatment, improve patient outcomes and quality of life, and reduce health care costs.