Commentary to Accompany
Many of us have been taught about the “Fight or Flight” response to a stressor as proposed by Cannon in the 1920s and 30s (1). The concept is often evoked to describe the heart rate response, and sometimes the acute sympathetic nervous system response, to a frightening stressor. It is also common experience that there is a link between psychological stress and eating behavior. The research community has provided ample evidence that overeating can be prompted by psychological stress in adults. There is also sufficient evidence that stress can increase cardiovascular disease (CVD) risk in adults. In the publication in the current issue, “Stress, Behavior, and Biology: Risk Factors for Cardiovascular Diseases in Youth,” Roemmich et al. investigate the important topic of how psychological stress reactivity is associated with atherogenesis in youth (3). They hypothesize that stress promotes atherogenic behaviors including snacking on energy dense foods and, perhaps more surprisingly, reduces physical activity, contributing to increased adiposity. They further propose that stress increases systolic blood pressure cardiovascular reactivity, and that exercise dampens stress reactivity, indicating a mechanism by which exercise protects against the development of cardiovascular diseases. They correctly focus on the interactions between behavioral (eating, sedentary, and exercise behavior) and physiological (systolic blood pressure, intima-media thickness) responses to stress to uncover resultant differences in CVD risk across groups of children.
While it may seem premature to worry about stress effects leading to CVD in youth, a 32-year prospective study has shown that stress in childhood can predict inflammation in adulthood as measured by circulating CRP-1 and several other markers of cardiovascular risk (2). Roemmich et al. also point out that the magnitude of increased CVD risk due to chronic stress is similar to the increased risk of CVD from hypercholesterolemia, diabetes, hypertension and smoking (3). They further present a series of their own insightful studies from 2002 onward investigating the interactions between obesity, dietary restraint, exercise, stress reactivity and CVD risk in children. In such studies, however, the total stress load is rarely addressed as most investigations used a single stressor. Children face multiple types of stressors throughout the day. The type, duration, magnitude and number of stressors and response to the stressors all dictate the total stress load and the resultant adverse effects. Overall well-being of the child and how this affects the family and community are more global issues that are impacted by this research. The particular stress load is likely unique within individuals as well as within and between given communities. Each of us can imagine sets of circumstances for children where total stress load would be the highest and worthy of the most study and intervention, but the complexity of this issue makes the choice of where to invest our resources difficult. A multi-level approach is likely warranted, as both the causes and effects are multi-level, from the individual to the family to the local community and beyond.
Perhaps the most important issue discussed in the highlighted review is how exercise, through a dampening of stress reactivity, produces a cardio-protective effect. The fact that they and others find signs of reduced cardiovascular risk in children by exercise is insightful in itself. It may be that the early fight or flight response was to allow immediate survival, but in modern times perhaps our children, as well as adults, should use the active flight response to improve our long-term survival? I do not propose to scare or stress people in to exercising: as Roemmich et al. report, some children are less likely to be physically active immediately following a stressor (3). Furthermore, children high in dietary restraint eat more following a stressor. The default coping behaviors of children, as in adults, to stress seem to promote obesity and increase CVD risk. An additional consideration is that getting children to exercise may be a stressor to the child. Clearly making the activity as enjoyable as possible for children is important. The question, partially addressed, is the type, intensity, duration and frequency of exercise necessary for the beneficial effects on CVD risk factors. The behavioral and physiological effects thus far shown have been typically from a single bout of exercise. One of the big remaining challenges in this area is therefore to determine the effects of physical activity and exercise training programs on stress reactivity and CVD risk in children. Or perhaps we should focus less on structured programs and more on daily play and physical activities in parks and other green environments?
Robert C. Hickner
Departments of Kinesiology and Physiology Center for Health Disparities
East Carolina University
Greenville, NC and Biokinetics
Exercise and Leisure Sciences School of Health Sciences
University of KwaZulu-Natal
Durban, S. Africa
1. Cannon W. B. The wisdom of the body
. New York, NY: W.W. Norton. 1932.
2. Danese A, Pariante CM, Caspi A. Childhood maltreatment predicts adult inflammation in a life-course study. Proc Natl Acad Sci U S A
. 2007; 104 (4): 1319–24.
3. Roemmich JN, Lambiase MJ, Balantekin KN, Feda DM, Dorn J. Stress, Behavior, and Biology: Risk Factors for Cardiovascular Diseases in Youth. Exerc. Sport Sci. Rev
. 2014; 42 (4): 145–52.