Michael T. Allen

Cardiovascular reactivity to stress predicts future blood pressure status.

Cardiovascular reactivity to stress may have a pathophysiological role in neurogenic hypertension. We studied the value of measuring blood pressure change during standardized mental and physical challenges to prediction of resting blood pressure status 6.5 years later among 206 middle-aged adults and their 164 children, with the latter group originally being tested while enrolled in elementary through high school. After adjustment for age, resting blood pressure, and body mass index at study entry, as well as length of follow-up, larger systolic and diastolic blood pressure responses to a combination of mental and physical challenges were associated with higher subsequent resting diastolic blood pressure 6.5 years later among adults. Among boys, but not among girls, larger systolic and diastolic blood pressure responses to challenge were associated with higher subsequent resting blood pressure. These data suggest that people who are at high risk for elevated blood pressure might have an exaggerated stress-induced cardiovascular response at a younger age.

Hemodynamic adjustments to laboratory stress: the influence of gender and personality.

&NA; Exaggerated cardiovascular reactivity to psychological stress is a potential pathophysiological mechanism linking behavior and cardiovascular disease. Because of the recognized gender differences in incidence of cardiovascular disease, potential gender differences in cardiovascular reactivity to laboratory stressors have been evaluated. The current study examined the cardiovascular responses of a total of 42 young women (N = 22) and men (N = 20) undergoing a laboratory protocol including the following: a nonverbal math task, a mirror tracing task, the Stroop Color‐Word interference task, and an isometric handgrip task. In addition to the assessment of heart rate and blood pressure, cardiac output, stroke volume, total peripheral resistance and preejection period were assessed by impedance cardiography. A number of personality characteristics that vary in prevalence by gender were also measured to evaluate their ability to explain potential gender differences in cardiovascular responses. Results indicated that men responded with greater total peripheral resistance and systolic and diastolic blood pressure responses than did women on a subset of tasks, whereas women exhibited larger increases in heart rate on a subset of tasks. Thus, men were more likely to be “vascular” reactors, with women being more likely to be “cardiac” reactors. Personality characteristics did differ between men and women, but did not explain significant variance in the gender differences in cardiovascular responses. We conclude that additional studies should focus on experimental manipulations of potential physiological mechanisms responsible for these differences, such as reproductive hormones.

Enhanced cardiovascular and catecholamine responses in women with depressive symptoms

To test the hypothesis that cardiovascular and sympathetic nervous system responses before and during behavioral stressors are exaggerated among subjects with depressed mood who do not have clinical depressive disorder. Sixty healthy women aged 18-49 were initially asked to complete the Beck Depression Inventory (BDI). The 15 with the highest (Depressive Symptom group) and the 15 with the lowest BDI scores (Control group) underwent stress testing including baseline, postural challenge, a speech task describing responses to a recent anger-arousing experience and recovery. Both systolic and diastolic blood pressure levels were higher in the Depressive Symptom group during baseline, challenges and recovery. This group also showed shorter pre-ejection period (a marker of enhanced cardiac sympathetic activation) and lesser heart rate variability across all test periods. During the speech task only, the Depressive Symptom group exhibited greater increases in plasma norepinephrine and higher cardiac output responses associated with decreased interbeat interval (faster heart rate). These results support the a priori hypothesis regarding enhanced sympathetic and cardiovascular activity. Finally, the BDI scores correlated very highly with lack of perceived emotional social support, reinforcing prior research on the linkage between social isolation and severity of depressive symptoms.

Hemoconcentration and stress: A review of physiological mechanisms and relevance for cardiovascular disease risk.

Elevated levels of hematocrit and hemoglobin have been identified as an independent risk factor for the development of a number of diseases, including hypertension, coronary heart disease, and stroke. A growing body of evidence also indicates that elevations in hematocrit and hemoglobin are present in situations involving both physical and mental stressors. This paper reviews the evidence linking decreases in plasma volume causing hemoconcentration with hemodynamic adjustments associated with activation of the sympathetic nervous system, and the potential relevance of stress-induced hemoconcentration in triggering deleterious cardiovascular events. The importance of blood viscosity in understanding the effects of hemoconcentration is discussed, along with the need to evaluate the degree of hemoconcentration during stress for accurate interpretation of changes in certain blood constituents.

Cardiovascular Reactivity to Stress and Left Ventricular Mass in Youth

We studied the relationships of cardiovascular reactivity during mental stress with left ventricular mass index in a group of prepubertal children 8 to 10 years old and in a group of peripubertal or postpubertal adolescents 15 to 17 years old. One hundred fifteen participants, varying in age group, sex, and race (black and white), took part in a laboratory stress protocol consisting of a reaction-time task, a mirror tracing task, a cold forehead challenge, and a stress interview. Cardiovascular measures included blood pressure and heart rate, as well as cardiac output, stroke volume, total peripheral resistance, and preejection period obtained noninvasively with impedance cardiography. Measures of left ventricular mass were made by echocardiography. Results indicated that across all participants, left ventricular mass index was associated with cardiovascular responses during the mirror tracing and cold forehead tasks, especially with those responses reflecting increased vasoconstriction. Subgroup analyses showed that these associations were significant for males and sometimes adolescents but not for females and children. As mirror tracing and cold forehead tasks most consistently produce alpha-adrenergic activation, the results suggest a model in which vasoconstriction due to mental stress is related to increased left ventricular mass in susceptible individuals, even at a young age.

Do cardiovascular responses to laboratory stress relate to ambulatory blood pressure levels ? : yes, in some of the people, some of the time

&NA; Because the correspondence between laboratory measures of blood pressure and heart rate responses to stress and ambulatory measures is less than optimal, this study tested two hypotheses: Are ambulatory measures of blood pressure elevated during periods of perceived stress, relative to no stress? Are ambulatory blood pressures elevated during perceived stress among those individuals who exhibit elevated blood pressure and heart rate responses to laboratory stress? These questions were addressed in a sample of employed, middle‐aged men and premenopausal and postmenopausal women, who vary in reproductive hormone status, and in risk for coronary heart disease. All participants performed a series of laboratory studies while their physiological parameters were monitored and then wore an ambulatory blood pressure monitor for a day and a half. This monitor recorded blood pressure every half hour during the waking hours and at the same time the participants assessed their mood states. After excluding participants who reported no variability in stress levels, those who were cardiovascular reactors to a laboratory speech task exhibited elevated ambulatory blood pressure levels during periods of perceived stress. Furthermore, in general, periods of perceived stress were associated on a within subject basis with elevated ambulatory blood pressure. These results suggest that the correspondence between laboratory and field measures of blood pressure would be improved by taking into account the environmental circumstances during the ambulatory assessments and the person characteristics of reactor‐nonreactor to laboratory stress.

DOES BACKGROUND STRESS HEIGHTEN OR DAMPEN CHILDREN'S CARDIOVASCULAR RESPONSES TO ACUTE STRESS?

Objective Does background stress heighten or dampen childrens cardiovascular responses to acute stress? Method To address this question, the cardiovascular responses to four acute laboratory stressors of 150 children and adolescents were evaluated according to their self-reported background stress level. Background stress was determined during a standardized interview and was a priori classified according to its importance, frequency, and whether it was ongoing or resolved. Results Results showed that children and adolescents who reported important stressors or stressors that were ongoing and frequent exhibited a larger increase in diastolic blood pressure and total peripheral resistance during all four laboratory stressors than their low stress counterparts. Additional analysis showed that the results could not be accounted for by sociodemographic variables or by the personality traits measured in this study. Conclusions Results suggest the importance of measuring background stress in understanding an individuals acute stress response.

Cluster analyses of cardiovascular responsivity to three laboratory stressors.

&NA; Seventy‐three young normotensive male subjects were tested with an experimental protocol that included a reaction time, a mental arithmetic, and a cold pressor task. Physiological variables that were recorded included heart rate, stroke volume, pre‐ejection period, blood pressure, total peripheral resistance, and respiratory sinus arrhythmia. In order to identify subgroups of subjects who differed in their pattern of autonomic responses to the tasks, the physiological change scores from baseline to the tasks for each subject were entered into a cluster analysis for each task. Wards method was used as the clustering algorithm. The cluster analyses identified four clusters for the reaction time and mental arithmetic tasks, and five clusters for the cold pressor task. Although there was a wide range of patterns exhibited by cluster subgroups, most subjects who were reactive to the tasks showed response patterns that were qualitatively similar to the pattern of overall mean response by all subjects, albeit varying considerably in terms of quantitative response. Little evidence was generated for the consistency of extreme beta‐adrenergic response from one task to another, although significant consistency was noted when milder beta‐responders were included in the comparisons. Some consistency of alpha‐adrenergic response noted across tasks, as well as significant consistency of being relatively nonreactive to the tasks.

Stability of cardiovascular reactivity to laboratory stressors: A 2 1 2 yr follow-up

The temporal stability of cardiovascular reactivity to laboratory stressors over a 2 1/2 yr period was studied. Subjects who had earlier received a cold pressor and a shock avoidance reaction time task were brought back for retesting using almost identical tasks. Cardiovascular variables that were common to both sessions included heart rate, systolic and diastolic blood pressure, and pre-ejection period. Correlations were computed to examine the association of responses across both sessions for the four cardiovascular variables during rest and the two tasks. Correlations of both heart rate and systolic blood pressure were high for all tasks and rest, whereas inconsistent correlations were found for diastolic pressure and pre-ejection period. Inconsistencies in diastolic pressure are speculated to be due to individual differences in beta-adrenergic response, whereas lack of consistent pre-ejection period associations may be due to differences in methodology. The results generally support the assumption of stability of cardiovascular reactivity.

The relationship of physiological responses to the coronary-prone behavior pattern in children

Forty-one male and female children were tested for Type A (coronary-prone) behavior using the Bortner test and the MYTH questionnaire. Based on their classification as A or B, three physiological variables were compared: systolic blood pressure (SBP), heart rate (HR) (phasic, tonic, and variability), and skin conductance (SC) (magnitude and latency of responses, number of spontaneous responses) during a 3-min rest period, a 10-min unsignaled reaction time (RT), and a 10-min word task. When using the Bortner to classify groups, Type As showed a tendency toward higher SBP levels and greater SBP reactivity to tasks, and significantly greater HR levels, HR reactivity to tasks, HR variability during rest, and SCR magnitude to RT signals. When using the MYTH, Type A females showed larger increases in SBP and HR to tasks, a lower mean HR, and a faster RT. Type A males showed a higher mean HR. Thus, children classified as Type A resemble Type A adults when compared on physiological responses to stress; however, the results depend on the method used to determine Type A behavior.