Dose Response Study of Aerobic Exercise in Older Adults

This is a randomized, 26-week study of supervised exercise assessing three doses of exercise in sedentary individuals 65 years of age and over with age-related cognitive changes. A total of 100 subjects (n=25 in each of four groups) will be randomized to a non-aerobic control group, 75 minutes, 150 minutes, or 225 minutes a week of moderate intensity aerobic exercise spread over 3 to 5 days a week for 26 weeks. These exercise doses represent 50%, 100%, or 150% of the recommended exercise dose. Participants will be directly supervised during all exercise sessions for the first two months after which direct supervision will occur during at least one session a week. This is intended to provide increased flexibility while also maintaining direct contact with the participant to enhance adherence. Aerobic fitness, physical function, and cognition will be assessed at baseline and 26 weeks to examine the dose-response relationships. At 52 weeks, cognition will be reassessed to examine durability of cognitive changes.

• Behavioral: Nonexercise control group
  Participants randomized to the nonexercise control group will be asked to maintain their current level of physical activity during the 26-week active study period. They will perform outcome assessments and receive the same telephone checks as the exercise group at baseline, 26 and 52 weeks. The purpose of including a non-exercise control group is to allow adequate comparisons with the low, medium and high exercise dose groups on changes in cognitive and physiologic outcome measures.
• Behavioral: Aerobic Exercise Group 1
  The 50% group will perform 75 minutes a week of moderate intensity exercise spread over 3 days.
• Behavioral: Aerobic Exercise Group 2
  The 100% group will perform 150 minutes a week of exercise over 3 - 5 days
• Behavioral: Aerobic Exercise Group 3
  The 150% group will perform 225 minutes a week of exercise over 4 - 5 days.

• Active Comparator: Nonexercise control group
  Intervention: Behavioral: Nonexercise control group
• Experimental: Aerobic Exercise Group 1
  Intervention: Behavioral: Aerobic Exercise Group 1
• Experimental: Aerobic Exercise Group 2
  Intervention: Behavioral: Aerobic Exercise Group 2
• Experimental: Aerobic Exercise Group 3
  Intervention: Behavioral: Aerobic Exercise Group 3

Inclusion Criteria:

• Informed consent
• Age 65 years or older
• Underactive or sedentary based on the Telephone Assessment of Physical Activity
• Community dwelling with a caregiver willing to accompany the participant to visits to the screening evaluation. The caregiver must visit with the subject more than five times a week.
• Nondemented: CDR 0
• Adequate visual and auditory abilities to perform all aspects of the cognitive and functional assessments
• Stable doses of medications for at least 30 days prior to screening.
• Likely to participate in all scheduled evaluations and complete the exercise program over 52 weeks

Exclusion Criteria:

• Dementia
• CDR > 0
• Current clinically significant major psychiatric disorder (e.g., Major Depressive Disorder) according to DSM-IV criteria or Geriatric Depression score of 5 or greater.
• Significant psychiatric symptoms (e.g., hallucinations) that could impair the completion of the study
• Current clinically-significant systemic illness likely to result in deterioration of the patient's condition or affect the patient's safety during the study
• History of clinically-evident stroke
• Clinically-significant infection within the last 30 days
• Myocardial infarction or symptoms of coronary artery disease (e.g., angina) in the last two-years.
• Uncontrolled hypertension within the last 6 months
• History of cancer within the last 5 years (except non-metastatic basal or squamous cell carcinoma)
• History of drug or alcohol abuse as defined by DSM-IV criteria within the last 2 years
• Insulin-dependent diabetes mellitus
• Significant pain or musculoskeletal disorder that would prohibit participation in an exercise program