PSYCHOBIOLOGIC REACTIVITY TO STRESS AND CHILDHOOD RESPIRATORY ILLNESSES - RESULTS OF 2 PROSPECTIVE STUDIES

Psychological stress is thought to undermine host resistance to infect ion through neuro endocrine-mediated changes in immune competence. Ass ociations between stress and infection have been modest in magnitude, however, suggesting individual variability in stress response. We ther efore studied environmental stressors, psychobiologic reactivity to st ress, and respiratory illness incidence in two studies of 236 preschoo l children. In Study 1, 137 3- to 5-year-old children from four childc are centers underwent a laboratory-based assessment of cardiovascular reactivity (changes in heart rate and mean arterial pressure) during a series of developmentally challenging tasks. Environmental stress was evaluated with two measures of stressors in the childcare setting. Th e incidence of respiratory illnesses was ascertained over 6 months usi ng weekly respiratory tract examinations by a nurse. In Study 2, 99 5- year-old children were assessed for immune reactivity (changes in CD4, CD8+, and CD19+ cell numbers, lymphocyte mitogenesis, and antibody r esponse to pneumococcal vaccine) during the normative stressor of ente ring school. Blood for immune measures was sampled 1 week before and a fter kindergarten entry. Environmental stress was indexed with parent reports of family stressors, and a 12-week respiratory illness inciden ce was measured with biweekly, parent-completed symptom checklists. Th e two studies produced remarkably similar findings. Although environme ntal stress was not independently associated with respiratory illnesse s in either study, the incidence of illness was related to an interact ion between childcare stress and mean arterial pressure reactivity (be ta = .35, p < .05) in Study 1 and to an interaction between stressful life events and CD19+ reactivity (beta = .51, p < .05) in Study 2. In both studies, reactive children sustained higher illness rates under h igh-stress conditions, but lower rates in low-stress conditions, compa red with less reactive peers. Stress was associated with increased rat es of illnesses, but only among psychobiologically reactive children. Less reactive children experienced no escalation in illness incidence under stressful conditions, suggesting that only a subset of individua ls may be susceptible to the health-altering effects of stressors and adversity.