Dimensions of psychobiologic reactivity: Cardiovascular responses to laboratory stressors in preschool children.

Individual differences in children's physiologic responses to environmental stressors may be responsible for significant, but modest, associations found in past studies between stress and various morbidities. Because no standardized approach currently exists for eliciting and measuring cardiovascular reactivity (CVR) to laboratory stressors in preschool children, we developed a laboratory-based reactivity protocol that derives three dimensions of CVR-intensity, variability, and attenuation-and collected reliability data for each. A sample of 137 children between the ages of three and five years completed a series of seven devel-opmentally challenging tasks, comprising interpersonal, cognitive, and fine motor problems. Pulse rate (PR), diastolic blood pressure (DBP), systolic blood pressure (SBP), and mean arterial blood pressure (MAP) were measured at twelve standardized points using a Dinamap oscillometric blood pressure monitor. CVR scores were calculated for each of the four cardiovascular measures using: (a) a difference score; (b) a standardized residual score; and (c) three scores characterizing the dimensions of intensity, variability, and attenuation. Four to six weeks following initial testing, the protocol was readministered to ascertain temporal stability of reactivity measures.All four cardiovascular measures were responsive to the presented tasks (p>.001), and extensive variability was found in the character of cardiovascular responses. Subjects less than four years of age showed higher task PRs and lower DBPs, SBPs, and MAPs compared to older peers, but no gender differences were found. Difference scores were highly correlated with standardized residual scores (r's=.94 and .79,p>.001 for PR and MAP, respectively), but the three reactivity dimension scores showed a lack of intercorrelation and were independent of both difference and residual scores. Only the intensity and variability dimension scores showed modest and significant test-retest reliability (r's=.25 to .50,P>.01). Although previous CVR research has generally utilized difference or residual scores, dimensional scores reflecting the intensity and variability of CVR may achieve greater reliability in preschool childen.