Psychophysiological theories on sympathetic nervous system reactivity in the development of essential hypertension

Beyond the new blood pressure guidelines: the beat goes on

The scope of hypertension (HTN) even for those involved in the field is staggering with numbers close to 60 million Americans and more than 1 billion individuals across the globe. It is the most common reason to seek medical attention and according to the World Health Organization, the number one cause of mortality in the world. Yet, we still don't know what is normal or abnormal. Even though the most recent 2017 Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults has created quite a commotion, new questions could be raised. The purpose of this Editorial not only to fuel more interest on this topic but also to create the notion that HTN needs to be considered a dynamic clinical entity rather than a static blood pressure reading.

Role of the orexin 2 receptor in palatable-food consumption-associated cardiovascular reactivity in spontaneously hypertensive rats

Hypertensive subjects often exhibit exaggerated cardiovascular reactivity. An overactive orexin system underlies the pathophysiology of hypertension. We examined orexin's roles in eating-associated cardiovascular reactivity in spontaneously hypertensive rats (SHRs) and Wistar-Kyoto (WKY) rats. Results showed eating regular chow or palatable food (sucrose agar) was accompanied by elevated arterial pressure and heart rate. In both SHRs and WKY rats, the cardiovascular responses associated with sucrose-agar consumption were greater than that with regular-chow consumption. Additionally, SHRs exhibited greater cardiovascular responses than WKY rats did to regular-chow and palatable food consumption. Central orexin 2 receptor (OX2R) blockade attenuated sucrose-agar consumption-associated cardiovascular response only in SHRs. In both SHRs and WKY rats, OX2R blockade did not affect regular-chow consumption-associated cardiovascular responses. Greater numbers of c-Fos-positive cells in the rostral ventrolateral medulla (RVLM) and of c-Fos-positive orexin neurons in the dorsomedial hypothalamus (DMH) were detected in sucrose agar-treated SHRs, compared to regular chow-treated SHRs and to sucrose agar-treated WKY rats. Central OX2R blockade reduced the number of c-Fos-positive cells in the RVLM only in sucrose agar-treated SHRs. We concluded that in SHRs, orexin neurons in the DMH might be overactive during eating palatable food and may further elicit exaggerated cardiovascular responses via an OX2R-RVLM pathway.

Cardiovascular reactivity in patients with essential or renal hypertension under standardized mental stress

Introduction. Patients with essential hypertension react more strongly to mental stress than normotensives. This may be related to the type of stress coping or to increased reactivity associated with the disease. The aim of our study was to examine whether patients with essential or secondary hypertension differ in their reaction to mental stress. Methods. Seventeen patients with essential hypertension (EH), 9 patients with renal hypertension (RH), and 22 normotensive controls (N) with no circulatory disorders were subjected to a psychophysiological examination under mental stress. Blood pressure (BP), heart rate (HR) and electrodermal activity (EDA) were measured. Results. The two hypertensive groups differed in their BP reaction to mental stress from the control group but not from each other. The product of heart rate and systolic blood pressure during the matrix test was significantly higher in essential than renal hypertensives (EH median: 13344; RH median: 12154.5; p = 0.04). This also holds true for the number of spontaneous fluctuations of EDA in the resting phase after the experiment (EH. median: 3.2; RH. median: 1.3; p = 0.01). Conclusion. The results suggest that not only a high blood pressure level but also the sympathetic nervous tone are responsible for the blood pressure response to mental stress. Due to very different (perhaps psychosocially triggered) conditions, essential hypertension leads to a stronger cardiovascular reaction under mental stress than renal hypertension.

Blood Pressure Biofeedback Exerts Intermediate-Term Effects on Blood Pressure and Pressure Reactivity in Individuals with Mild Hypertension: A Randomized Controlled Study

OBJECTIVE

This randomized controlled study examined whether a 4-week blood pressure (BP) biofeedback program can reduce BP and BP reactivity to stress in participants with mild hypertension.

METHODS

Participants in the active biofeedback group (n=20) were trained in 4 weekly laboratory sessions to self-regulate their BP with continuous BP feedback signals, whereas participants in the sham biofeedback group (n=18) were told to manipulate their BP without feedback signals. BP, skin temperature, skin conductance, BP reactivity to stress, body weight, and state anxiety were assessed before training and repeated at the eighth week after the training.

RESULTS

The decreases in systolic (12.6 +/- 8.8 versus 4.1 +/- 5.7) and mean BP (8.2 +/- 6.9 versus 3.3 +/- 4.9) from baseline at week 12 follow-up were significantly greater in the active biofeedback group compared with the sham biofeedback group (p=0.001 and 0.017, respectively). Results from analysis of covariance with the follow-up systolic blood pressure (SBP) (or mean arterial pressure [MAP]) as the dependent variable, baseline SBP (or MAP) as the covariate, and group as the independent variable showed that biofeedback training effectively lowered SBP and MAP (p=0.013 and 0.026, respectively). The pre-to-post differences in skin conductance and SBP reactivity were statistically significant for the biofeedback group (p=0.005 and 0.01, respectively), but not for the control group. For the sample as a whole and for the biofeedback group, the state anxiety score and body weight remained unchanged.

CONCLUSIONS

BP biofeedback exerts a specific treatment effect in reducing BP in individuals with mild hypertension, possibly through reducing pressor reactivity to stress.

Cardiovascular reactivity of patients with essential and renal hypertension in an emotion-triggering interview

Blood pressure reactivity to mental stress in hypertensives is much higher than in normotensives. The authors' aim in this study was to examine whether different cardiovascular responses can be induced by various stimuli in hypertensive subgroups. The authors matched 10 essential hypertensives (EHs), 10 renal hypertensives (RHs), and 10 normotensives (Ns) according to age and gender examined them during an emotion-stimulating interview, and measured blood pressure (BP) and heart rate (HR) during the phases of the interview. They observed differences in BP reactivity between EHs/RHs and Ns under some stimuli but not between EHs and RHs, as well as a marked difference in the product of systolic BP (SBP) and HR between both hypertensive groups in the anger/rage phase (p = .028) and the baseline 2 (p = .02). This shows a higher cardiovascular activation under mental stress and a lower recovery in EHs and more sensitivity to perturbation or higher central tension compared with RHs.

The relationship of blood pressure and cortisol reactivity to family history of hypertension of African American adolescents

Ethnicity and family history of hypertension (FHH) have been associated with the development of hypertension. Blood pressure and cortisol reactivity during physiologic stress are hypothesized to function as biologic markers for hypertension. The purpose of this study was to explore the relationship of blood pressure and cortisol reactivity physiologic to FHH in a selected sample of African American adolescents.

METHODS

Demographic data and physiologic measurements were obtained from 48 African American adolescents (14-17 years). Reactivity was induced by a cold pressor test of hand immersion in cold water. chi, t tests, and multivariate repeated-measures analysis were used to determine relationships.

RESULTS

Thirty-one (65%) subjects reported an FHH. Thirty (63%) subjects demonstrated cardiovascular reactivity. Although the mean systolic blood pressure was 4 mm Hg higher, t tests indicated no significance between group in systolic blood pressure (P = .32), diastolic pressure (P = .73), and cortisol (P =.81). Blood pressure reactivity of the FHH group was significantly different than the no family history group (P = .0338). Cortisol levels for the total group were markedly elevated (19 nmol/dL) and there was no significant difference in reactivity.

CONCLUSION

African American adolescents with FHH demonstrate increased blood pressure reactivity. Cortisol levels were elevated for all participants. This study adds support to the association of blood pressure reactivity, a biologic marker of HTN and FHH.

Normal exercise blood pressure response in African-American women with parental history of hypertension

BACKGROUND

Genetic and environmental hypotheses may explain why normotensive persons at high risk of developing hypertension often exhibit greater cardiovascular reactivity to stressors than those at low risk.

METHODS

Pearson's correlation was used to evaluate reproducibility and independent t test to compare the cardiovascular responses to 30 W of exercise of normotensive young adult African-American women with positive and negative parental histories (PH) of hypertension (PH, n = 23; PH, n = 20).

RESULTS

Correlations were significant for duplicate measurements. The effects of PH on blood pressure measured at rest and during exercise were not statistically significant (P > 0.1). A nearly significant trend for greater resting (.-)VO(2) (P = 0.08) was detected in the PH than in the PH group (3.67 +/- 0.18 versus 3.26 +/- 0.14 mL/kg/min).

CONCLUSION

A hyper-reactive blood pressure response to exercise, characteristic of the evolution of hypertension, may not be present among the normotensive female offspring of hypertensive African Americans. The significance of an 11% intergroup difference in the mean resting (.-)VO(2) observed in this study is unclear.

Trait anger, anger expression, and ambulatory blood pressure: a meta-analytic review

A meta-analysis of 15 studies was conducted to investigate the relationship between trait anger and ambulatory blood pressure. Overall, the experience of anger was significantly and positively associated with systolic blood pressure (r+ = 0.049), but not reliably associated with diastolic blood pressure (r+ = 0.028). After removing an outlier, the expression of anger was found to have a reliable inverse relationship with diastolic blood pressure (r+ = -0.072). No reliable relationship between expression of anger and systolic blood pressure (r+ = -0.041) was found. These results continue to support the modest role of self-reported trait anger and anger expression in blood pressure levels. Several suggestions for future research are discussed, including increasing the focus on the complexity and synergism of these effects.

Positional change in blood pressure and 8-year risk of hypertension: the CARDIA Study

OBJECTIVE

To assess the relationship between positional blood pressure change and 8-year incidence of hypertension in a biracial cohort of young adults.

SUBJECTS AND METHODS

Participants from the Coronary Artery Risk Development in Young Adults (CARDIA) study with complete data from year 2 (1987-1988), year 5 (1990-1991), year 7 (1992-1993), and year 10 (1995-1996) examinations were included (N = 2781). Participants were classified into 3 groups based on their year 2 systolic blood pressure response to standing: drop, a decrease in systolic blood pressure of more than 5 mm Hg; same, a change of between -5 and +5 mm Hg; and rise, more than 5-mm Hg increase.

RESULTS

The number of participants in each group was as follows: drop, 741; same, 1590; and rise, 450. The 8-year incidence of hypertension was 8.4% in the drop group, 6.8% in the same group, and 12.4% in the rise group (P < .001). Adjusted odds ratios for developing hypertension during the follow-up period in the rise group vs the same group were as follows: in black men, 2.85 (95% confidence interval [CI], 1.43-5.69), in black women, 2.47 (95% CI, 1.19-5.11), in white men, 2.17 (95% CI, 1.00-4.73), and in white women, 4.74 (95% CI, 1.11-20.30).

CONCLUSIONS

A greater than 5-mm Hg increase in blood pressure on standing identified a group of young adults at increased risk of developing hypertension within 8 years. These findings support a physiologic link between sympathetic nervous system reactivity and risk of hypertension in young adults.

Blood pressure response to heart rate during exercise test and risk of future hypertension

Previous works have shown that exaggerated blood pressure response to exercise is a valid risk marker for future hypertension, yet the use of an exercise test as a means of early prediction of hypertension still requires methodological development and confirmation. The purpose of this study was to determine abnormal ranges of blood pressure responses in relation to heart rate increase during exercise and to examine the clinical utility of exercise blood pressure measurement in evaluating individual risk for developing hypertension. We examined exercise test data from a population-based sample of 1033 nonmedicated normotensive men (mean age, 42.9+/-8.5 years; range, 20 to 59 years). Percentile curves of systolic and diastolic blood pressure responses to relative heart rate increments during submaximal exercise were constructed using a third-order polynomial model with multiple regression analysis. Of the original study sample, a cohort of 726 subjects was followed for hypertensive outcome for an average period of 4.7 years. Progression to hypertension, defined as a blood pressure of > or =140/90 mm Hg or the initiation of antihypertensive therapy, was found in 114 subjects (15.4%). Kaplan-Meier survival estimates showed that the cumulative incidence of hypertension increased progressively with higher percentiles of systolic and diastolic blood pressure response (both, P<0.01). A Cox proportional survival analysis revealed a significantly increased risk for developing hypertension associated with exaggerated blood pressure response to exercise after multivariable adjustments for traditional risk factors (relative risk, 3.8; 95% confidence interval, 2.3 to 6.1). These results suggest that an exaggerated blood pressure response to heart rate during exercise is predictive of future hypertension independent of other important risk factors and lend further support to the concept that blood pressure measurement during exercise test is a valuable means of identifying normotensive individuals at high risk for developing hypertension.

Reproducibility of blood pressure and heart rate reactivity: a meta-analysis

Reproducibilities of blood pressure and heart rate (HR) reactivity reported in studies assessing responses to the same laboratory stressors across occasions were reviewed with meta-analytic techniques. Changes in HR had the greatest reproducibility (r = .555), followed by systolic blood pressure (SBP) (.407) and diastolic blood pressure (DBP) (.348). Both SBP and HR response reproducibility was higher at shorter test-retest intervals, whereas DBP values varied unsystematically with length of test-retest interval. Older samples exhibited higher SBP and DBP reproducibility to stressors. SBP and DBP reproducibilities were better for tasks that did not make speech demands. The reliability of reactivity assessment was higher when based on three or more measurements. On the basis of available evidence, the drop in stress reproducibility, as test-retest interval increases, places limits on the viability of BP reactivity as a strong marker or risk factor for coronary heart disease.

Autonomic reactivity and alcohol-induced dampening in men at risk for alcoholism and men at risk for hypertension

Both sons of male alcoholics with multigenerational family history of male alcoholism (MFH) and sons of essential hypertensives (HTs) exhibit elevated psychophysiological reactivity to stress when compared with male controls (FH-). MFHs also demonstrate a significant baseline heart rate increase and stress-response dampening following alcohol consumption. The present study investigates the specificity of this alcohol-induced psychophysiological response pattern by testing these two risk groups in a shock response paradigm, both sober and alcohol-intoxicated. A repeated measures analysis of variance on sober and alcohol-intoxicated heart rate reactivity yielded a significant risk by alcohol interaction, indicating that alcohol consumption led to a greater decrease in reactivity in the MFH group compared with the HT and FH- groups. Similar results were obtained for muscle tension measures. MFHs also displayed greater increases in resting baseline heart rate and muscle tension when alcohol intoxicated. The results may reflect a sensitivity to negatively and positively reinforcing effects of alcohol specific to individuals with multigenerational familial histories of alcoholism.