Active Voice: Physical Activity Promotes Healthy Brain Function?
By Rui Liu, Ph.D and Jim Laditka, D.A., Ph.D.

Viewpoints presented in SMB commentaries reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM.

Rui Liu, Ph.D., is a postdoctoral fellow at the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health. Her research focuses on environmental factors, physical activity, and neurodegenerative disease outcomes. Jim Laditka, D.A., Ph.D., is an Associate Professor of Public Health Sciences at the University of North Carolina at Charlotte. Dr. Laditka worked with the CDC and the Alzheimer’s Association as Co-Chair of the Steering Committee that produced The Healthy Brain Initiative: A National Public Health Roadmap for Maintaining Cognitive Health. This commentary presents Drs. Liu’s and Laditka’s views associated with the research article they and their colleagues published in the Feb.2012 issue of Medicine & Science in Sports & Exercise® (MSSE), titled “Cardiorespiratory Fitness as a Predictor of Dementia Mortality in Men and Women.”

In the report of our study, recently published in MSSE, we examined whether being physically active reduces the risk of dying with dementia. Nearly 60,000 participants completed a treadmill exercise test measuring cardio-respiratory fitness, an objective indicator of physical activity habits. We followed participants for an average of 17 years and then linked their data with the National Death Index to identify those who had died with dementia.

Based on the treadmill test, we ranked participants as least-fit, middle-fit, or high-fit. Compared to the least-fit, the middle- and high-fit had less than half the risk of dying with any type of dementia, including Alzheimer’s disease. The middle-fit had only about a quarter of the risk of dying with vascular dementia, the second most common type of dementia.

People do not have to be athletes to be in the middle-fit group. Walking briskly most days of the week will keep the majority of people in that group, as will other, equivalent types of physical activity. The basic recommendation of the 2008 Physical Activity Guidelines for Americans for older adults is two hours and 30 minutes of moderate-intensity physical activity every week, which is enough to keep most people in the middle-fit group.

After reviewing the scientific evidence, the ACSM concluded that cardiovascular fitness and higher levels of physical activity reduce the risk of cognitive decline and dementia. The ACSM Position Stand rated the strength of available evidence between “strong” and “overwhelming.” Our study supports that conclusion, particularly because we used an objective physical activity measure.

Our related research shows that many adults want to be physically active, but face barriers including lack of age-appropriate programs and places for physical activity, lack of knowledge about physical activity or experience with it, or unsafe walkways, crosswalks, or neighborhoods. Policy commitments and community support for accessible physical activity options are likely to reduce the prevalence of many chronic diseases. Our study and many others in the last decade suggest that dementia may be among them.

Other related research we have completed shows that people often share with clinicians their concerns about cognitive health. Clinicians told us they face barriers when responding. They have limited time with patients. Some find it hard to keep up with the literature. Patients often have more pressing needs. Advising patients about physical activity is rarely reimbursed. Yet, clinicians should consider promoting the ACSM’s guidelines. Doing so may do as much good as many medical regimens, and often has less risk.

Like all science, our findings are not certain. We did not conduct a randomized clinical trial (RCT), the “gold standard” for science. There are few RCTs in this area. Most have design problems that limit their usefulness. We may never have an RCT large enough and long enough to provide convincing evidence. For now, the conclusion of the ACSM and the results of our study suggest we may substantially reduce people’s risks of dying with dementia by promoting physical activity. Doing so is a reasonable practice with limited risk and large known health benefits.