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Studies by Arnold School doctoral student, alumna show physical activity may sustain mental health
February 20, 2012
Dr. Andrew A. Young, editor-in-chief of Medicine & Science in Sports & Exercise®, the official journal of the American College of Sports Medicine, has singled out two important studies by Arnold School of Public Health researchers in his editorial for the February issue.
John Sieverdes, a doctoral candidate in the Department of Exercise Science, is the lead author on an article about a study that examined the effects of physical activity on mental health. Dr. Rui Liu, who earned her doctoral degree from the Arnold School’s Department of Epidemiology and Biostatistics in 2010, is the lead author on an article that is one of the first reports to examine the relationship between objectively measured cardiorespiratory fitness levels and dementia-related deaths in a sample of nearly 60,000 adults.
In his editorial, Young writes, “MSSE’s February issue features two articles addressing effects of physical activity on mental health. Sieverdes et al. report a study of over 9,500 adult men in which the prevalence of symptoms of mental depression decreased, as levels of leisure-time physical activity increased. The authors note that the reduction in the risk of depressive symptoms began accruing even at activity levels below those currently recommended for maintaining physical health.
“In the other article, Liu et al. report on the association between cardiorespiratory fitness and dementia mortality in a very large prospective cohort studied over an average duration of 17 years. This study, which was unique in that fitness was quantified using objectively measured indices, demonstrated that higher cardiorespiratory fitness was associated with lower risk of Alzheimer’s disease mortality, vascular disease mortality, and total dementia mortality. Both studies indicate that meeting physical activity recommendations will not only produce physical health benefits, but may also help sustain mental health.”
Liu, who conducted the study for her dissertation, collaborated with Arnold School researchers Dr. Steven Blair and Dr. Mei Sui and former faculty members Dr. James Laditka and Dr. Natalie Colabianchi.
Public health efforts in the U.S. have triggered gradual declines in deaths associated with heart disease, breast cancer and stroke over the past few years. Deaths related to dementia and Alzheimer’s disease, however, have increased dramatically over the last 15 years, skyrocketing 46 percent between 2002 and 2006.
Researchers conducted baseline examinations and maximal exercise tests for 14,811 women and 45,078 men, ages 20-88 years, at the Cooper Clinic in Dallas. Baseline examinations included self-reported personal and family medical history, a questionnaire on demographic information and health habits, blood chemistry tests, and other clinical measurements. Participants were grouped into one of three fitness categories – low fit, middle fit or high fit – based on their fitness test performance.
“A major strength of our study is the use of standardized and objective physical activity measurement,” said Liu, a postdoctoral fellow at the National Institute of Environmental Health Sciences, part of the National Institutes of Health. “Cardiorespiratory fitness is preferable to self-reported physical activity because it is an objective, reproducible measure that is more closely correlated with a person’s usual level of physical activity and many health outcomes.”
By Dec. 31, 2003 (an average of 17 years after the baseline examinations), there were 4,047 deaths. The National Death Index attributed 164 of these mortalities to dementia (72 vascular dementia and 92 Alzheimer’s disease). Of the 164 individuals whose deaths were related to dementia, 123 were in the low-fit category, 23 were in the medium-fit category and 18 were in the high-fit category. Compared to the least-fit individuals, those in the medium- and high-fitness groups had less than half the risk of dying with dementia.
“These findings support physical activity promotion campaigns by organizations such as the Alzheimer’s Association and should encourage individuals to be physically active,” said Liu. “Following the current physical activity recommendations from the American College of Sports Medicine will keep most individuals out of the low-fit category and may reduce their risk of dying with dementia.”
Sieverdes’ article, “Association between Leisure Time Physical Activity and Depressive Symptoms in Men,” examined the association between depressive symptoms and physical activity (PA) in a sample of 9,580 men, ages 20 – 87 years old, from the Aerobics Center Longitudinal Study. There were 727 men with depressive symptoms.
The study found lower odds of depressive symptoms across all categories of leisure-time physical activity, which was measured as approximately 150 minutes per week – or 30 minutes of activity (such as walking) on five days of the week.
“This corresponds to the current physical activity guidelines for preventing other health conditions such as cardiovascular disease,” Sieverdes said.
Of particular interest, obese men (defined as having a BMI of 30 or greater) reported having fewer depressive symptoms even when participating in less than an equivalent of 150 minutes of moderate intensity physical activity.
“Our findings support the need for behavioral interventions aimed at increasing physical activity; interventions targeting inactive men may be particularly important. Those meeting recommendations would not only experience physical health benefits but may also reduce the likelihood of depressive symptoms. Such reductions could have a significant public health effect in terms of disability, quality of life, and cost,” said Sieverdes.
The study’s co-authors from the Arnold School included Dr. Mei Sui, Dr. Duck-chul Lee, Dr. Greg Hand, Meghan Baruth, Dr. Steven Blair and Billy M. Ray, a recent USC graduate.
This is the second time that the ACSM has singled out a study by Sieverdes. A 2010 study that found men with low levels of cardiorespiratory fitness are 60 percent more likely to die of stroke than men who are moderately fit or highly fit was featured at the annual meeting of the ACSM.
Sieverdes will be a post-doctoral fellow at the SmartState Technology Center for Healthful Lifestyles of the Medical University of South Carolina, which is partnering with the University of South Carolina and the Arnold School of Public Health.
