Is the hypertensive rat really hyperreactive?

This study investigated the behavior of hypertensive-prone and nonhypertensive-prone rat strains to see whether there are differences in behavioral reactivity to environmental stimulation. Of primary interest was general activity, because investigators have assumed it to be an index of reactivity to environmental stimulation and to be correlated with the elevation of blood pressure in spontaneously hypertensive rats (SHR) but not in normotensive Wistar-Kyoto (WKY) rats. Therefore, general activity was assessed in SHRs and WKYs as a function of walking and rearing in an open field (Experiments 1 and 2) and crossings in a shuttlebox test (Experiments 3, 4, and 5). Activity was assessed under a constant level of environmental stimulation in the open field (Experiment 1) and shuttlebox (Experiment 3) or under varying degrees of stimulation in the open field (Experiment 2) and shuttlebox (Experiments 4 and 5). In the open field and the shuttlebox, SHR activity was above WKY activity when the degree of environmental stimulation was constant. However, when stimulation was manipulated, the SHR activity level was similar for all intensity levels, while the WKY activity was inversely related to stimulus intensity. These results suggest that while the SHRs may generally be more active than WKYs, WKYs display a greater behavioral reactivity to environmental stimulation than SHRs.

Family characteristics and school achievements of type A children.

We examined the familial characteristics of Type A children and the consequences of Type A behaviors for children's classroom achievements. A maximum of 156 boys and 190 girls enrolled in elementary and middle schools and their parents participated in various aspects of the data collection procedures and analyses reported in this article. Results showed that Type A children were not more likely to have families with a history of cardiovascular-related diseases or families of upper socioeconomic status. Young Type A boys, but not girls, had Type A mothers and fathers, suggesting an early modeling of Type A behaviors by boys. Competitive boys and girls and Type A girls had higher achievement test scores and classroom grades, independent of IQ test scores, than did relatively noncompetitive children and Type B girls, respectively. Thus, the competitive aspect of Type A leads to important early achievements, independent of ability, perhaps because care givers and teachers respond to Type A behaviors of children by encouraging them to continue to strive to achieve. Gender differences in the findings were also discussed and related to the adult literature.

Lipid reactivity to stress: I. Comparison of chronic and acute stress responses in middle-aged airline pilots.

Lipids increase during psychological stress, but no studies have compared the effects of acute and chronic stressors on lipid responsivity in the same individuals. One hundred middle-aged men (n = 92) and women (n = 8) were examined during high chronic occupational stress, low chronic stress, and acute laboratory stressors. In addition to measures of perceived stress and affect, an extensive battery of lipid and lipoprotein measures was undertaken at each time point. Most lipid parameters were significantly increased during the chronic and acute stressors, although the responses to the different stressors were not consistently associated. For example, significant correlations among the chronic and acute stress responses were apparent for the apoproteins, but not for total, low density lipoprotein, or high density lipoprotein cholesterol. The factors and processes regulating these variables during stress may be different during acute and chronic stressors.

Lipid reactivity to stress: II. Biological and behavioral influences.

This study examined behavioral and physiological influences on lipid concentrations during acute and chronic stressors. One hundred men (n = 92) and women (n = 8) were tested during a chronic stressor and during 2 acute stressors. During chronic stress, diet, physical activity, exercise, and sleep were examined. During the acute stressors, catecholamines, cortisol, plasma volume, and cardiovascular responses were examined. None of the behavioral influences could explain the lipid response to chronic stress. Responses of the atherogenic lipids to acute stressors were not solely reflecting hemoconcentration of the plasma but were moderately correlated with cardiovascular, epinephrine, and cortisol reactivity. Diastolic blood pressure reactors to the acute stressors had larger lipid responses to the chronic stressor than did nonreactors. Elevations in blood lipids during stress are not artifacts and may be clinically significant.

Does the gender relevance of the stressor influence sex differences in psychophysiological responses?

Sex differences in psychophysiological responses to stress may be important to understanding sex differences in risk for coronary heart disease. This investigation tested the hypothesis that the gender relevance of the stressor influences the extent of sex differences in cardiovascular, neuroendocrine, and lipid responses during stress. Participants performed two tasks that were described as masculine oriented, feminine oriented, or not gender relevant. Although these descriptions influenced the participants' perceptions of the tasks, they did not influence the extent of sex differences in physiological responses in a manner consistent with the study hypothesis. Future directions for research are discussed regarding sex differences in psychophysiological responses.

A natural experiment on the effects of ovarian hormones on cardiovascular risk factors and stress reactivity: bilateral salpingo oophorectomy versus hysterectomy only.

To test the effects of declining ovarian hormone levels on cardiovascular risk factors, blood pressure, lipids, weight, and physiological responses to stress were evaluated in 29 middle-aged premenopausal women prior to and following elective hysterectomy and/or bilateral salpingo oophorectomy (BSO). Prior to surgery, there were no group differences in standard or putative risk factors, with the exceptions of body composition measures and total cholesterol level. After surgery, women who had undergone BSO (n = 10) had higher levels of atherogenic lipids and stress-induced lipids and tended to have higher circulating levels of epinephrine and stress-induced systolic and diastolic blood pressure than women who had undergone hysterectomy only (n = 19). This study is consistent with the hypothesis that presence of ovarian hormones plays a key role in determining women's risk factor status.

Gender and ethnicity in children's cardiovascular reactivity: 7 years of study.

A total of 295 children (127 White boys, 15 Black boys, 133 White girls, and 20 Black girls) participated in reactivity examinations in 1987 (all were in 3rd grade; age, M = 9.1 years), 1988, 1989, 1991, 1992 and 1993 (all were in 9th grade; age, M = 15.1 years). An analysis of residualized reactivity change values indicated consistent and significant ethnicity effects (Blacks greater than Whites) for systolic and diastolic blood pressure and for heart rate. Gender effects were also apparent for both systolic and diastolic blood pressure (boys greater than girls). These data suggest that the transition from childhood to adolescence is associated with a significant pattern of ethnic differences in reactivity, although the association of this pattern with the development of cardiovascular risk and disease remains to be ascertained.

Influence of age, sex, and family on Type A and hostile attitudes and behaviors.

We describe the influence of age, sex, and family on Type A and hostility indices that have been related to rates of coronary heart disease (CHD). The sample consisted of 120 girls and 95 boys (ages 6 to 18 years) and 141 women and 120 men (ages 31 to 62 years) from 142 families residing in an upper middle class community. Results showed little familial aggregation of Type A and hostility. Adults had higher Structured Interview (SI) Potential for Hostility ratings than did children, whereas children had higher Minnesota Multiphasic Personality Inventory (MMPI)-derived Hostility scores and SI Anger-In ratings than did adults. Male adults and male children had higher SI Potential for Hostility ratings and MMPI-derived Hostility scores than did their female counterparts. The heightened hostility of males may account, in part, for their heightened risk of CHD relative to females'.

Plasma homocysteine levels increase in women during psychological stress.

Homocysteine is an amino acid that has been strongly associated with vascular disease. Plasma homocysteine concentrations are known to vary with dietary patterns and to decrease with exogenous estrogen use, but no other behavioral factors have been examined as potential modifiers of this risk factor. Because psychological stress has also been implicated in the development of cardiovascular disease, the purpose of this study was to test the hypothesis that acute psychological stress induces elevations in plasma homocysteine concentrations. A secondary aim was to test potential differences in response between premenopausal and postmenopausal women. Thirty-four healthy women, one-half of whom were naturally postmenopausal with no hormone replacement, participated in this study. The psychological stressors included standard mental arithmetic and speech stressors. Blood samples were taken prior to, during, and after the stressors, and heart rate and blood pressure were also monitored. Results indicated significant elevations in plasma homocysteine during acute psychological stress, with a return to baseline concentrations during recovery. The pattern of findings for blood pressure and heart rate was similar, suggesting that the rise in homocysteine concentrations may have been sympathetically-mediated. No effects of menopausal status or endogenous estrogens were found. The findings provide preliminary evidence that plasma homocysteine may be an important factor in the relationship between psychological stress and risk for heart disease.

Plasma homocysteine concentrations are positively associated with hostility and anger.

Homocysteine is a sulphur amino acid that is positively associated with risk of vascular disease. Very few behavioral or psychological factors have been studied in relationship to homocysteine levels, despite the fact that several psychological factors have also been linked with risk for cardiovascular disease. One psychological attribute showing a strong association with risk is hostility, which is prospectively predictive of future cardiovascular disease endpoints. Another related psychological factor is anger expression; coronary heart disease risk is associated with both heightened expression and inhibition of anger. The purpose of this study was to test the relationship of hostility and anger expression with homocysteine concentrations in a sample of healthy, middle-aged men and women. Participants completed the Cook-Medley hostility questionnaire, the Speilberger Anger Expression questionnaire, and had blood taken for the assessment of plasma homocysteine concentrations. Results indicated positive and significant associations between hostility and homocysteine levels for all participants, and positive and significant correlations between anger-in and homocysteine levels for men only. These data are among the first to test the relationship between homocysteine and psychological risk factors for cardiovascular diseases, and suggest one potential mechanism for the increased cardiovascular risk associated with hostility and anger expression.

Are cardiovascular reactors to asocial stress also reactors to social stress?

The authors tested the generalizability of measures of cardiovascular reactivity to asocial and social stress among fathers, mothers, and their adolescent sons. Results showed significant associations between reactivity to individual psychomotor tasks and to conflict resolution only for mothers, suggesting that laboratory measures of reactivity obtained during asocial tasks are of limited value in predicting reactivity during social tasks. Given that interpersonal constructs are important to risk for cardiovascular diseases, these findings point to the importance of measuring cardiovascular reactivity during social stress, not only during asocial achievement stress.

Lipids in psychological research: the last decade.

We review the recent literature examining lipid changes during stressful experiences, and the psychological and constitutional differences that influence lipid levels at rest and that may modulate lipid response to stress. Mild forms of chronic or episodic stress are apparently not associated with alterations in lipids and lipoproteins, but severe forms of real or perceived stress do appear to alter lipid levels. Acute laboratory stress is frequently associated with short-term alterations in lipids and lipoproteins, but the significance of these changes is unclear. Several individual characteristics, such as heightened neuroendocrine or autonomic reactivity to stressors, Type A component behavior, and other aspects of personality, appear to be associated with an atherogenic lipid profile. Stress may influence lipid concentrations and metabolism through a variety of physiological and behavioral mechanisms, but none have been clearly elucidated. Future research should concentrate on understanding these mechanisms.

Influences of sex and age on cardiovascular responses during stress.

The present investigation examined the influence of sex and age on blood pressure and heart rate responses in 125 women, 93 men, 121 girls, and 96 boys to three standardized stressors: serial subtraction, mirror-image tracing, and isometric handgrip. With baseline measures and body mass index controlled for, analyses of covariance showed that adults had greater systolic blood pressure responses than did children; men had greater blood pressure responses to all stressors than did women; and high school boys had greater systolic blood pressure responses than did high school girls. In addition, adults had smaller heart rate responses during isometric handgrip than did children, and high school students had smaller heart rate responses during all tasks than did the remaining, younger students. These results show that sex and age are important determinants of the magnitude of cardiovascular adjustments during stressors. The implications of these results are discussed in light of sex differences in coronary heart disease morbidity and mortality.

Depressed mood is related to high-frequency heart rate variability during stressors.

OBJECTIVE: The purpose of this study was to examine the relationships between depressed mood and parasympathetic control of the heart in healthy men and women at rest and during two stressors. METHODS: Fifty-three healthy college students completed a laboratory stress protocol that included a baseline resting period, a challenging speech task, and a forehead cold pressor task. Depressed mood was assessed using the Beck Depression Inventory (BDI). Parasympathetic cardiac control was measured as the high-frequency (0.12-0.40 Hz) component (HF) of heart rate variability using power spectrum analysis. Blood pressure, respiration rate, and respiration amplitude were measured simultaneously. RESULTS: Participants were categorized as having a high or low depressed mood on the basis of median splits of their BDI scores. Those in the high depressed mood group had significantly greater reductions in HF during the speech task and significantly smaller increases in HF during the forehead cold pressor task than those in the low depressed mood group. Women had significantly greater reductions in HF during the speech task and smaller increases in HF during the forehead cold pressor task than men. However, gender and depressed mood did not interact to predict changes in HF. CONCLUSIONS: Depressed mood is related to the magnitude of decrease in parasympathetic cardiac control during stressors in healthy men and women. These findings extend those of previous studies, in which a similar phenomenon was observed among patients with cardiac disease. Because the participants in this study were healthy, the relationship between depressed mood and parasympathetic cardiac control does not seem to be secondary to cardiovascular disease.

Lipid reactivity among men with a parental history of myocardial infarction.

In the current study, we examined lipid and cardiovascular responses to an acute stressor among men with and without a parental history of myocardial infarction. 37 men were selected from a large group who completed medical history questionnaires and interviews. Twenty-two men who denied parental history of heart disease (negative parental history) were compared with 15 men with one or both parents who had suffered a myocardial infarction (positive parental history). Total cholesterol, high- and low-density lipoprotein cholesterol, triglycerides, heart rate, and blood pressure were measured at rest and during a videotaped speech stressor. Positive parental history men had significantly higher low-density lipoprotein cholesterol levels and blood pressure at baseline, significantly lower high-density lipoprotein cholesterol levels at baseline, and significantly larger total cholesterol and low-density lipoprotein cholesterol reactivity, relative to negative parental history men. Because parental history is a risk factor for subsequent cardiovascular morbidity and mortality, these data suggest that lipid reactivity to stress may be biologically important.

Catecholamine stress responses in arterialized blood.

Arterialized and venous blood was compared to determine if the arterialization procedure enhances the detection of stress-related changes in catecholamines. Lipid and hematologic measures were also compared for possible distortion by arterialization. Fifteen men completed two stressors. Indwelling venous catheters were placed retrograde in each hand, and the right hand was warmed to a constant temperature. Blood samples were taken simultaneously from both hands, and plasma catecholamines were determined. Arterialization increased baseline epinephrine; there were no effects of arterialization on catecholamines during stress, nor in lipid or hematologic measures during baseline or stress. Thus, arterialization of blood results in small increases in resting epinephrine levels, but does not obscure lipid measures. More importantly, arterialization of venous blood does not enhance the detection of stress-related changes in catecholamines.

Anger expression and lipid concentrations.

We used 2 different strategies to examine the relation between anger expression and lipid concentrations in 116 middle-aged men. Using the common analytic method used in the literature, the group crossing approach, we examined whether Anger-In. Anger-Out, and their interaction were related to lipids. Regression analyses revealed that Anger-In and Anger-Out were marginally related to total cholesterol. These associations disappeared after controlling for hostility, anger, and anxiety. Using a new intraindividual difference approach, we determined individuals' relative dominance of Anger-In and Anger-Out and examined linear and quadratic associations with lipids. Regression analyses revealed the quadratic was related to both total cholesterol and low-density lipoprotein-cholesterol (LDL-c), indicating that individuals who almost always express their anger or almost never express their anger had both elevated total cholesterol and LDL-c. The curvilinear association with total cholesterol persisted even after controlling for hostility, anger, and anxiety.