| Exaggerated cardiovascular reactivity to psychological stress has been linked to a number of disorders including hypertension, coronary heart disease, artheroscierosis, and myocardial infarction. An emerging line of research has emphasized pediatric populations as recent findings suggest that the pathogenesis of cardiovascular diseases originates in childhood. To convincingly assert that children's cardiovascular reactivity contributes to subsequent cardiovascular disease, it is essential to demonstrate that: (a) cardiovascular reactivity in childhood is a stable individual difference, and (b) children with an increased risk for developing hypertension or cardiovascular disease have exaggerated reactivity. The present investigation was the follow-up to a three-year longitudinal study. The temporal stability, inter-task consistency, and laboratory-to-field generalizability of children's cardiovascular reactivity was evaluated. The relationship among cardiovascular reactivity and three well-established risk factors (family history, Type A, anger expression) also was examined. Twenty-three children (Mage = 13.0 years) participated in a two-phase psychophysiological assessment. During the laboratory phase, impedance cardiography and blood pressure measures were collected during baseline, serial subtraction, isometric handgrip, and mirror-image tracing conditions, and rest intervals. The children then completed a twenty-four hour ambulatory assessment phase in which blood pressure and heart rate were assessed. The impedance variables demonstrated moderate temporal stability (r avg = .49) and high inter-task consistency (r avg = .83), while the blood pressure variables exhibited the least stability. The laboratory-to-field generalizability was low among blood pressure measures (ravg = .19), though heart rate was found to be moderately consistent (ravg = .56). Higher-risk children exhibited lower and less stable reactivity compared to lower-risk children. However, the consistency, or heterogeneity, of the reactivity correlations was greater among higher-risk individuals. The results supported the notion that children's cardiovascular reactivity is a stable individual difference. Examination of the patterns of reactivity suggested higher-risk children exhibited lower contractility, slower rhythm, higher output, and lower pressure compared to lower-risk children. Taken together, the findings support the diathesis-stress model of cardiovascular reactivity. Limitations of the study included power, sample characteristics, psychometric considerations, and situational differences. Future researchers should establish a standardized reactivity protocol, develop methodological criteria for ambulatory assessment, and use continuous blood pressure recording equipment whenever possible. |
