Volume 13, Number 11
“Compared with most women/men your age, would you say that you are more physically active, less active, or about the same?”
It may seem that this question is irrelevant for your own personal health, because how physically active you are is what affects your health, not how your physical activity compares to others… right? Not so fast. If this were the case, this edition of e-quilibrium wouldn’t be raising the question.
Doctors Octavia Zahrt and Alia Crum of Stanford University analyzed data obtained from two ongoing national surveys conducted by the National Center for Health Statistics, and published their results in the most recent edition of Health Psychology. The two surveys from which data were taken are the National Health Interview Survey (NHIS) and the National Health and Nutrition Examination Survey (NHANES). These surveys include questions regarding respondents’ perceptions of how their physical activity level compares to that of others their age. The surveys also ask about actual activity. The earliest survey data used were from 1990, which provided a follow-up period of 21 years. The most recent component of their data came from NHANES surveys beginning in 2003, important because at that point NHANES began using accelerometers to obtain objective data on actual physical activity.
The primary outcome of interest to the investigators was mortality, that is, death from any cause. Their primary finding was that persons who perceived themselves to be less physically active than their age peers were 71% more likely to have died in the follow-up period than were those who saw themselves as more physically active. Notably, this result persisted even when objective levels of physical activity, health status, and other health behaviors were controlled in the analyses.
Interestingly, the correlation between perceived levels of physical activity and actual levels of physical activity was low. Among those who were physically inactive, approximately 20% viewed themselves as more active than others while 30% perceived themselves to be less physically active than their peers. This means that subjective perceptions and social comparisons of physical activity must be understood as distinct from actual physical activity. The research literature is accumulating more studies that indicate that subjective perceptions themselves have an impact on behavior, emotion, and physiology. In fact, changing perceptions of physical activity (i.e., convincing persons that they are more physically active than they believe themselves to be), even when physical activity doesn’t change, has been demonstrated to result in actual health improvements.
Of course, actual physical activity is a major contributor to better health, and studies indicate that even small amounts of physical activity reduce mortality risk. So the implication from the results obtained by the Stanford investigators is not that one should simply focus on perceiving that one is more physically active than one’s peers (although their data suggest that this is a healthy thing to do), but rather that one should be physically active AND believe that one’s level of physical activity is more than that of one’s peers.
Paul J. Hershberger, Ph.D.
… is a clinical health psychologist. He is Professor and Director of the Division of Behavioral Health, Department of Family Medicine, Wright State University Boonshoft School of Medicine.
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