Systolic blood pressure reactivity during submaximal exercise and acute psychological stress in youth.

Cardiovascular disease (CVD) is the leading cause of death in the United States.1 Advances in noninvasive imaging technology have allowed in vivo study of the structural and functional properties of the arterial system and can be used in pediatric populations to identify youth at greater risk for developing CVD later in life.2–6 Studying CVD risk factors in children and adolescents is important because the antecedents of CVD occur in youth,7–9 decades before any clinical signs or symptoms appear.4,8 A growing literature shows an association between cardiovascular reactivity (CVR) to acute psychological stress and subclinical CVD risk in youth, with several studies showing an association between systolic blood pressure (SBP) reactivity to laboratory psychological stress tasks and carotid artery intima-media thickness (CIMT) in independent samples of children9 and adolescents.10,11 However, the mechanisms by which transient increases in blood pressure (BP) may contribute to future CVD are not well understood. A limitation of assessing CVR in a laboratory setting is that CVR is greatly influenced by the characteristics of the stressor.12 A majority of studies in both adults and youth utilize psychological stress tasks to assess CVR. However, the use of different tasks between studies, in addition to subject factors that can affect CVR to psychological stressors (e.g., ability, motivation, previous experience with task), makes comparisons between studies challenging and may hinder identification of the precise mechanisms whereby CVR is associated with CVD risk. To most efficiently increase our understanding of how CVR in youth contributes to future CVD, it will be important to employ stressors that can be replicated for comparison across studies, that produce cardiovascular responses similar in magnitude to those encountered in a natural environment, and that are useful in identifying individuals at greater risk for CVD throughout the lifespan.13 Submaximal exercise produces cardiovascular adjustments similar to that produced by acute psychological stress. Notably, the workload of submaximal exercise tests can be objectively determined, and BPs during submaximal intensities are comparable with the range of BPs encountered during everyday activities in youth. Moreover, in children, SBP reactivity to running has been shown to be more reliable over time than SBP reactivity to psychological stress.13 If SBP reactivity during submaximal exercise can identify youth at risk for future CVD as well as or better than traditional psychological stress tasks, the use of standardized exercise protocols may increase the reliability of CVR measurement. However, it is not yet known whether SBP reactivity during submaximal exercise is associated with CIMT in youth, as it is during psychological stress. The purpose of this study was to test the following hypotheses: (i) SBP reactivity during submaximal exercise is associated with CIMT, similar to SBP reactivity during acute psychological stress and (ii) SBP reactivity during submaximal exercise is associated with SBP reactivity during psychological stress tasks.