Medpedia

According to the article cited below,  "Physically active adults have a lower risk of depression and cognitive decline than inactive adults. In a study of 1,740 persons 65 years and older without a diagnosis of dementia at baseline, those who exercised at least three times a week were much less likely than nonexercisers to develop dementia or Alzheimer disease. Additionally, participating in an activity, especially regular physical exercise, appears to decrease the risk of delirium in hospitalized older patients. In a study of 779 newly hospitalized patients 70 years and older without dementia, regular exercise lowered the risk of delirium by 24 percent."

In 2008, the U.S. Department of Health and Human Services released guidelines to provide information and guidance on the amount of physical activity recommended to maintain health and fitness. 

Recommendations for Physical Activity in Older Adults

Minimum activity for achieving important health benefits: Two hours and 30 minutes (150 minutes) of moderate-intensity aerobic activity (e.g., brisk walking) a week, plus muscle-strengthening activities on at least two days of the week.

or one hour and 15 minutes (75 minutes) of vigorous-intensity aerobic activity (e.g., jogging, running) a week, plus muscle-strengthening activities on at least two days of the week

or a combination of moderate- and vigorous-intensity aerobic activity equivalent to the recommendations above, plus muscle-strengthening activities on at least two days of the week

Increased activity for achieving additional health benefits

Five hours (300 minutes) of moderate-intensity aerobic activity a week, plus muscle-strengthening activities on at least two days of the week

or two hours and 30 minutes (150 minutes) of vigorous-intensity aerobic activity a week, plus muscle-strengthening activities on at least two days of the week

or a combination of moderate- and vigorous-intensity aerobic activity equivalent to the recommendations above, plus muscle-strengthening activities on at least two days of the week.

Abstract: PubMed. "Physical activity guidelines for older adults," American Family Physician [2010 Jan 1;81(1):55-9].  Image: Andy Newson / FreeDigitalPhotos.net