Cross-sectional study on respiratory effect of toner-exposed work in manufacturing plants, Japan: pulmonary function, blood cells, and biochemical markers.

The aim of the study is to examine the relationship between toner-exposed work and health indices related to respiratory disorders and to confirm the baseline of a cohort study to clarify the effect of toner exposure in manufacturing plants. Subjects were 1614 male workers (809 toner-exposed workers and 805 referents) who were engaged in toner manufacturing plants in Japan (Fuji Xerox Co., Ltd). The age of subjects was from 19 to 59 years, and the average age was 40.2 years(median 40 years, SD 7.67). We conducted a pulmonary function test (PEFR, VC, FVC, FEV(1.0)%, V25/Ht) and a blood cell test (RBC, Hb, Hct, Plt, WBC, cell contents of WBC) and measured biochemical indices in blood (ALT, AST, gamma-GTP, CRP, IgE) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in urine. Student t-test and logistic regression analysis were applied to compare between the toner-exposed workers and the referents and to analyze the relationship among indices of effects and independent factors. There was no significant difference between the two groups in blood cell count and biochemical indices. Inflammation- and allergy-related markers such as 8OHdG and IgE also showed no significant difference between toner-exposed workers and the referents. The influence of smoking on pulmonary function indices was observed, but there was no relationship between the pulmonary function and toner-exposed work. In this article, we report a preliminary cross-sectional analysis in the subjects of a cohort study. No difference in pulmonary function indices was observed between the toner-exposed workers and the referents, and there was no consistent relationship between the exposure status and examined indices; however, the prevalence of subjective respiratory symptoms was higher in the exposed workers as presented in another report. Further analysis is important in the ongoing cohort study to clarify the effect of toner exposure on respiratory systems.

Heterogeneity in the social networks of young and older adults: prediction of mental health and cardiovascular reactivity during acute stress.

We examined the utility of a broad framework that separated positive, negative, and ambivalent social network members. One hundred thirty-three young and older participants completed the social relationships index, measures of mental health, and a cardiovascular reactivity protocol. Results replicated prior research on the beneficial influence of positive (supportive) ties on psychological outcomes. More important, analyses also revealed that the number of ambivalent network ties predicted age-related differences in depression and sympathetic control of heart rate reactivity during stress. The statistical interactions between age and ambivalent ties on cardiovascular responses during stress were not changed when statistically controlling for other social network categories, demographic variables, and various personality factors. These data suggest that social network ambivalence was a relatively unique predictor of cardiovascular reactivity and highlight the utility of separating the variance due to positive, negative, and ambivalent network ties. Implications for the study of social relationships, physiological processes, and health outcomes are also discussed.

Autonomic and neuroendocrine responses to mild psychological stressors: effects of chronic stress on older women.

We investigated autonomic and endocrine responses to acute stressors in 27 women who were or are presently caring for a spouse with a progressive dementia (high chronic stress) and 37 noncaregivers who were category matched for age and family income (low chronic stress). Measures were taken before (low acute stress) and in response to brief laboratory stressors (high acute stress). We replicated prior research showing that caregivers report greater stress, depression, and loneliness than the comparison groups, and acute stressors elevate autonomic and neuroendocrine activity. We also found that caregivers, relative to noncaregivers, exhibited shorter preejection periods and elevated blood pressure and heart rate, but the magnitude of autonomic and neuroendocrine reactivity to the experimental stressors was comparable across these groups. This pattern of autonomic differentiation replicates prior research showing that caregivers are characterized by higher sympathetic activation than noncaregivers and suggests that the effects of chronic stress on physiological reactivity may be a less robust effect in older adults.

Vigilance, active coping, and cardiovascular reactivity during social interaction in young men.

This study of 72 undergraduate men examined the effects of two determinants of cardiovascular response-active coping and vigilance-on blood pressure and heart rate responses to social stressors. Observation of a future debate partner (i.e., vigilance) evoked larger increases in blood pressure than did observation of a less relevant person, apparently through the combination of increases in cardiac output and vascular resistance. Preparation and enactment of efforts to exert social influence (i.e., active coping) evoked heightened blood pressure and heart rate responses through increased cardiac contractility and output. Thus, both vigilance and active coping in social contexts increased cardiovascular reactivity, but apparently through different psychophysiological processes.

Social support and age-related differences in cardiovascular function: an examination of potential mediators.

The investigators examined the potential influence of social support on age-related differences in resting cardiovascular function and the potential mediators responsible for such associations in 67 normotensive women and men. Consistent with prior research, age predicted increased resting systolic blood pressure (SBP) and diastolic blood pressure (DBP). More importantly, regression analyses revealed that social support moderated age-related differences in resting SBP and DBP, as age predicted higher resting blood pressure for individuals low in social support, but was unrelated to blood pressure for individuals high in social support. An examination of potential pathways revealed that these results were not mediated by various health-related variables, personality factors, or psychological processes. Implications for the study of social support and health are discussed.

Age-related differences in cardiovascular reactivity during acute psychological stress in men and women.

We examined potential age and gender differences in cardiovascular reactivity during acute psychosocial stress in 133 normotensive participants using a cross-sectional design. Results revealed that age predicted increased systolic blood pressure (SBP) reactivity during stress (p < .001). The greater SBP reactivity found in older individuals appeared due to an age-associated increase in both cardiac output and total peripheral resistance during stress as statistically controlling for these changes rendered the age and SBP reactivity effect nonsignificant. Similar analyses revealed that the age-related increase in cardiac output reactivity appeared to be driven by increased cardiac sympathetic control of myocardial contractility as measured by pre-ejection period. Older individuals also had greater vagal withdrawal during stress compared to younger individuals as indexed by respiratory sinus arrhythmia (p < .01). These results were comparable for men and women, and could not be explained by task-specific affective responses, task performance, or demographic factors. Implications for the study of age, cardiovascular reactivity, and health are discussed.

The availability of social support reduces cardiovascular reactivity to acute psychological stress.

The influence of the availability of social support on cardiovascular reactivity to acute psychological stress was examined. Twenty-eight men and twenty-one women performed a speech task either in a support availability or no support availability condition while measures of systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were assessed. Consistent with past research, the speech stressor was associated with significant increases in SBP, DBP, and HR. More important, the availability of social support moderated cardiovascular reactivity to the acute stressor: individuals in the support availability condition were characterized by lower SBP and DBP reactivity to the acute stressor compared to individuals in the no support availability condition. These data suggest that simply having potential access to support is sufficient to foster adaptation to stress in the absence of enacted support.

The relationship between social support and physiological processes: a review with emphasis on underlying mechanisms and implications for health.

In this review, the authors examine the evidence linking social support to physiological processes and characterize the potential mechanisms responsible for these covariations. A review of 81 studies revealed that social support was reliably related to beneficial effects on aspects of the cardiovascular, endocrine, and immune systems. An analysis of potential mechanisms underlying these associations revealed that (a) potential health-related behaviors do not appear to be responsible for these associations; (b) stress-buffering effects operate in some studies; (c) familial sources of support may be important; and (d) emotional support appears to be at least 1 important dimension of social support. Recommendations and directions for future research include the importance of conceptualizing social support as a multidimensional construct, examination of potential mechanisms across levels of analyses, and attention to the physiological process of interest.

Appraisal support predicts age-related differences in cardiovascular function in women.

The influence of appraisal support on age-related differences in cardiovascular function was examined. Resting assessments of heart rate, systolic blood pressure (SBP), diastolic blood pressure (DBP), respiratory sinus arrhythmia (RSA), and preejection period were obtained from 45 young and 20 elderly women. Consistent with prior research, results revealed that the elderly women had higher blood pressure and lower RSA than the young women. More important, appraisal support predicted age-related differences in SBP and DBP: Age predicted elevated blood pressure for women low in appraisal support, whereas age was unrelated to blood pressure for women high in appraisal support. These preliminary data suggest that appraisal support may be an important predictor of long-term physiological function and health.

Individual differences in cardiac sympathetic control predict endocrine and immune responses to acute psychological stress.

Potential mechanisms coordinating individual differences in cardiovascular reactivity and endocrine and immune responses to acute psychological stress were examined. Twenty-three young, healthy women performed a mental arithmetic challenge while measures of cardiovascular, endocrine, and immune function were assessed. Results revealed that the acute stressor was associated with changes in the cardiovascular, endocrine, and immune systems. More important analyses revealed that individual differences in cardiovascular reactivity predicted stress-induced cortisol changes. Furthermore, cardiac sympathetic control, as indexed by preejection period, was specifically related to changes in natural killer cell activity. These results suggest that distinct physiological pathways are activated in response to acute psychological stress.

Heterogeneity in neuroendocrine and immune responses to brief psychological stressors as a function of autonomic cardiac activation.

Human responses to brief psychological stressors are characterized by changes and large individual differences in autonomic, neuroendocrine, and immune function. The authors examined the effects of brief psychological stressors on cardiovascular, neuroendocrine, and cellular immune response in 22 older women to investigate the common effects of stress across systems. They also used interindividual variation in heart rate reactivity, cardiac sympathetic reactivity (as indexed by preejection period reactivity in their reactivity paradigm), and cardiac vagal reactivity (as indexed by respiratory sinus arrhythmia reactivity) to explore the heterogeneity in human responses to brief psychological stressors. The results revealed that brief psychological stressors heightened cardiac activation, elevated plasma catecholamine concentrations, and affected the cellular immune response. It was also found that individuals characterized by high, relative to low, cardiac sympathetic reactivity showed higher stress-related changes in adrenocorticotropic hormone and cortisol plasma levels but comparable changes in epinephrine and norepinephrine concentrations. These data suggest that the effects of psychological stressors on cardiovascular and cellular immune response are governed by coordinated regulatory mechanism(s) and that going beyond the simple notion of heart rate reactivity to examine neural substrates may shed light on the interrelationships among and the regulatory mechanisms for the autonomic, endocrine, and immune responses to stressors.

Autonomic cardiac control. II. Noninvasive indices and basal response as revealed by autonomic blockades.

Heart period, systolic time intervals, low and high frequency heart period variability, blood pressure, and respiration were measured in female subjects under three drug conditions (saline, atropine sulfate, metoprolol) while sitting and standing on three consecutive days. Following preinfusion baseline recordings, saline, metoprolol (14 mg), or atropine sulfate (2 mg) was infused for 15 min (by using a double-blind procedure). Recordings were taken during a postinfusion baseline and in response to an orthostatic stressor (standing versus sitting postures). At the end of the metoprolol session, atropine sulfate was infused and responses were monitored during the postinfusion (i.e., double blockade) baseline and during orthostatic stressor. Analyses of the blockade data revealed that the preejection period (PEP) reflected sympathetic but not vagal influences on the heart, and high frequency (HF, 0.12-0.40 Hz) heart rate variability (respiratory sinus arrhythmia) reflected vagal but not sympathetic influences on the heart. No other measure provided a specific index of the tonic sympathetic or vagal activation of the heart. Postinfusion PEP under saline predicted individual differences in postinfusion cardiac sympathetic activation, whereas postinfusion heart period (but not HF variability) under saline predicted individual differences in postinfusion cardiac vagal activation.

Autonomic cardiac control. III. Psychological stress and cardiac response in autonomic space as revealed by pharmacological blockades.

Behavioral contexts can evoke a variety of autonomic modes of response, characterized by reciprocal, coactive, or independent changes in the autonomic divisions. In the present study, we investigated the reactive autonomic control of the heart in response to psychological stressors, using quantitative methods for analyzing single and double autonomic blockades, and through the use of noninvasive indices based on heart period variability and systolic time intervals. Analysis of the effects of pharmacological blockades revealed an overall pattern of increased sympathetic and decreased parasympathetic control of the heart during speech stress, mental arithmetic, and a reaction-time task. Unlike the classical reciprocal sympathetic-parasympathetic response to orthostatic challenge, however, the responses of the autonomic branches to stress were uncorrelated. This reflected notable individual differences in the mode of autonomic response to stress, which had considerable stability across stress tasks. The putative noninvasive indices of sympathetic (preejection period) and parasympathetic (respiratory sinus arrhythmia) control changed in accord with the results of pharmacological blockades. Together, these results emphasize the substantial individual differences in the mode of autonomic response to stress, the advantages of a quantitative approach to analyzing blockade data, and the importance of validity estimates of blockade data.

Individual differences in the autonomic origins of heart rate reactivity: the psychometrics of respiratory sinus arrhythmia and preejection period.

Heart rate reactivity has been conceptualized, at least implicitly, as a unidimensional construct ranging from low to high, reflecting individual differences in adrenergic reactivity to daily stressors. However, an individual's classification as high in heart rate reactivity ignores possible individual differences in the autonomic origins of this reactivity. Sixty-eight women were exposed to orthostatic and speech stressors to determine the psychometric properties (postural stability, convergent and discriminant validity) of heart rate, preejection period, and respiratory sinus arrhythmia. Results revealed that (a) basal, stress, simple reactivity (stress - baseline), and residualized change indices of heart rate, preejection period, and respiratory sinus arrhythmia were stable across postures and (b) heart rate reactivity was significantly related to preejection period and respiratory sinus arrhythmia reactivity, whereas the latter two measures were unrelated. Reactivity classifications may therefore be significantly improved by attention to concurrent estimates of the activity of both autonomic branches.

The effects of an acute psychological stressor on cardiovascular, endocrine, and cellular immune response: a prospective study of individuals high and low in heart rate reactivity.

High and low reactors were preselected on the basis of their heart rate reactivity to a speech stressor in a prescreening session. In the main study, subjects were exposed to a mental arithmetic plus noise stressor. Cardiovascular activity was recorded during baseline and stressor, and blood was drawn prior to and following the stressor for endocrine and immune assays. Results revealed that the stressor decreased the blastogenic response to concanavalin A and increased natural killer cell numbers and cytotoxicity, absolute numbers of CD8+ T-lymphocytes, norepinephrine and epinephrine levels, heart rate, and blood pressure responses. In addition, cortisol and natural killer cell cytotoxicity responses to the stressor differentiated individuals high versus low in heart rate reactivity. These results suggest that the interactions among the autonomic nervous system, endocrine system, and immune system are not only amenable to psychophysiological analysis but that such analyses may play an important role in illuminating underlying mechanisms.

Origins of baseline variance and the Law of Initial Values.

The Law of Initial Value (LIV) asserts that the magnitude of a phasic psychophysiological response is dependent on the initial baseline level. Although results in accord with the LIV are often observed, exceptions are frequent, especially for between-subjects analyses. A general assumption in studies of the LIV is that a given baseline difference is equivalent regardless of its functional origin. The present study examined the relationships between basal heart period variance, arising from alternate sources, and the magnitude of the chronotropic response to a speech stressor. Results reveal that baseline differences due to orthostatic manipulations, which are known to be largely of autonomic origin, yielded larger LIV effects than did individual differences in basal heart period, which include a significant nonautonomic component. The minimal LIV-like effects of baseline differences associated with non-autonomic factors, relative to variations in autonomic control, may contribute to the inconsistent appearance of between-subjects LIV effects.

Construals of preillness relationship quality predict cardiovascular response in family caregivers of Alzheimer's disease victims.

The authors examined the relationships between family caregivers' construal of their preillness affection for and cohesiveness with an Alzheimer's disease (AD) patient and subsequent cardiovascular functioning. Scale validation demonstrated the psychometric properties. In a study conducted 2 years later, 31 family caregivers of AD victims performed stress-inducing tasks while cardiovascular activity was monitored. Path analyses revealed that caregivers relatively high in preillness affection for the AD patient were characterized by lower heart rate reactivity and resting diastolic blood pressure. In contrast, caregivers relatively high in preillness cohesion were characterized by higher resting systolic and diastolic blood pressure. These results suggest that caregivers' social relationships may play an important, although not always beneficial, role in cardiovascular regulation and health.

The problem of equivalent models in applications of covariance structure analysis.

For any given covariance structure model, there will often be alternative models that are indistinguishable from the original model in terms of goodness of fit to data. The existence of such equivalent models is almost universally ignored in empirical studies. A study of 53 published applications showed that equivalent models exist routinely, often in large numbers. Detailed study of three applications showed that equivalent models may often offer substantively meaningful alternative explanations of data. The importance of the equivalent model phenomenon and recommendations for managing and confronting the problem in practice are discussed.

Age-related changes in cardiovascular response as a function of a chronic stressor and social support.

The effects of aging, chronic stress, and social support on cardiovascular functioning were examined using a cross-sectional design. Thirty-six family caregivers of Alzheimer's disease victims and 34 control Ss performed 2 active coping tasks while continuous noninvasive measures of cardiovascular activity were monitored. Results revealed that caregivers high in social support displayed typical age-related decreases in heart-rate reactivity, whereas caregivers low in social support displayed age-related increases in heart-rate reactivity. Analyses further indicated that only Ss with low social support were characterized by age-related increases in systolic blood pressure. These results suggest that social support can moderate age-related changes in cardiovascular functioning, particularly in Ss exposed to a chronic stressor.

Relationship between facial expressiveness and sympathetic activation in emotion: a critical review, with emphasis on modeling underlying mechanisms and individual differences.

Two important questions bearing on personality processes and individual differences are how do facial expressiveness and sympathetic activation vary as a function of the intensity of an emotional stimulus, and what is the functional mechanism underlying facial expressiveness and sympathetic activation in emotion? A formulation is proposed that is based on 2 propositions: (a) All strong emotions result in some degree of activation of the organism (i.e., principle of stimulus dynamism) and (b) there are individual differences in the gain (amplification) operating on the facial expressive and sympathetic response channels (i.e., principle of individual response uniqueness). This formulation organizes much of the existing data on internalizers and externalizers and yields novel predictions regarding the subpopulation labeled as generalizers.