Vagal rebound and recovery from psychological stress.

OBJECTIVE: To characterize cardiovascular recovery and examine the possible relationship of vagal activity and reflexes to risk for heart disease. METHODS: Subjects performed cold pressor and mental arithmetic tasks. Heart rate, heart period variability, and pre-ejection period were obtained for 1 minute before, during, and after each task (Experiment 1). In the second experiment, subjects performed a Stroop color-word task and a mental arithmetic task. Heart rate, heart period variability, blood pressure, and baroreflex sensitivity were obtained during the 5-minute baseline, task, and recovery periods (Experiment 2). RESULTS: In Experiment 1, heart rate during recovery was lower than baseline despite continued pre-ejection period shortening, whereas recovery heart period variability was higher than baseline. In Experiment 2, blood pressure increased throughout the session. However, recovery heart rate after mental arithmetic was lower than baseline heart rate, and heart period variability was higher during both recovery periods than during baseline. Vagal rebound, a sharp increase in variability in the first minute of recovery, was reduced in men in Experiment 1 and in individuals with a family history of cardiovascular disease in Experiment 2 and was associated with degree of change in baroreflex sensitivity between task and rest. CONCLUSIONS: Cardiovascular recovery from stress is associated with increased vagal modulation despite residual sympathetic activation. Vagal rebound may be involved in mechanisms resetting the baroreflex sensitivity at the onset and offset of stress. Diminished vagal rebound during recovery from stress is associated with standard risk factors for cardiovascular disease. The results support an association between attenuated vagal reflexes and risk for cardiovascular disease.

Breast-feeding and maternal cardiovascular function.

Two studies examined the effects of breast-feeding on maternal cardiovascular function. In the first experiment, groups of breast-feeding and bottle-feeding women were compared on preejection period (PEP), heart rate (HR), cardiac output (CO), and total peripheral resistance (TPR) recorded for 1-min periods before and during standard laboratory stressors. Compared with bottle-feeders, breast-feeders had higher CO throughout the session, and greater decreases in CO and increases in TPR during cold pressor. In the second experiment, HR and blood pressure (BP) were compared before and after one breast-feeding and one bottle-feeding session in a within-subjects design. Both feeding methods increased BP but decreased HR, and systolic BP was higher for the breast-feeding than the bottle-feeding condition. Both studies support the notion that breast-feeding alters maternal cardiovascular function, possibly through the actions of oxytocin.

A preliminary study of breast-feeding and maternal symptomatology.

The association between breast-feeding status and maternal health is examined. A survey questionnaire was presented via the World Wide Web. Self-reports of 168 breast-feeding and 65 weaned mothers between 4 and 208 weeks postpartum were compared for physician visits, symptomatology, and Perceived Stress Scale scores in the last month. Breast-feeding was associated with fewer physician visits and symptoms and less perceived stress. Moreover, the longer a woman breast-fed before she weaned, the fewer the symptoms and less stress she reported. Breast-feeding is associated with better maternal health both during the breast-feeding period and after weaning. Further research on the effects on maternal health of breast-feeding is indicated. Future prospective longitudinal investigations should address the possible inhibition of lactation by stress and physiological mechanisms that may link breast-feeding and weaning with maternal health.

Psychosocial stress and social support are associated with prostate-specific antigen levels in men: results from a community screening program.

Perceived stress and satisfaction with social support were assessed in 318 men participating in a prostate-specific antigen (PSA) screening program. We predicted that high stress would be associated with high PSA and high social support with low PSA. We also predicted a Stress x Support interaction (buffering). Hypothesized main effects were confirmed and were not explained by recency of previous rectal examinations or current urinary symptoms. There was no evidence of buffering. Stress and social support were not associated with results of digital rectal examinations. These findings raise the possibility that psychosocial factors promote prostate disease through direct physiologic pathways. However, it is also possible that the data reflect effects of stress on health-related behaviors or that stress scores were affected by participants' anticipation of prostate problems on the basis of prior PSA tests or symptoms.

The effects of epinephrine administration on impedance cardiographic measures of cardiovascular function.

The effects of epinephrine administration on cardiovascular function were examined in 26 men who were given a bolus injection of either 1:10,000 epinephrine hydrochloride or physiological saline. Impedance cardiographic and continuous blood pressure measures were recorded during a 2-min pre-injection baseline and in the post-injection period. Compared to a saline control, epinephrine elicited greater shortening of heart period, pre-ejection period, and the R-B interval; greater increases in cardiac output, stroke volume, dZ/dt amplitude, Heather Index, and systolic and diastolic pressures; and greater decreases in total peripheral resistance (all P < 0.05). Left ventricular ejection time and the Q-R interval were not affected. The results indicate that inotropic indices that are readily measured by impedance cardiography should be considered as important non-invasive indices of adrenergically mediated responses to stress.

The ensemble-averaged impedance cardiogram: an evaluation of scoring methods and interrater reliability.

The interrater reliability and concurrent validity of two methods of scoring the ensemble-averaged impedance cardiogram were evaluated. Impedance cardiographic and electrocardiographic signals were recorded from 40 undergraduate men and women during a baseline rest period and a vocal mental arithmetic task period. Recordings were scored by four rates using a conventional method, involving ensemble averaging after careful editing of beat-to-beat waveforms, and a streamlined method, involving ensemble averaging without beat-to-beat editing. Intraclass correlations for interrater reliability exceeded .92, whereas intraclass correlations for concurrent validity exceeded .97, indicating excellent agreement between rates and scoring methods for all cardiac measures. The streamlined method was significantly faster than the conventional method. The results indicate that variations in beat-to-beat editing do not constitute a serious source of error in the ensemble-averaged impedance cardiogram and support the interrater reliability and concurrent validity of the two scoring methods.

A preliminary study of the effects of breast-feeding on maternal health.

This study is a preliminary investigation of the effects on breast-feeding and cessation of breast-feeding on maternal health. A self-report questionnaire assessed overall health, mood, stress, and psychological and upper respiratory infection symptoms in 14 current, 36 never, and 49 past breast-feeders. Results indicated that breast-feeding did not incur greater health costs to the mother compared with bottle-feeding and that cessation of breastfeeding was associated with worse mood, more stress, and a greater number of psychological symptoms compared with current breast-feeding. Physiological mechanisms, as opposed to personality factors, are discussed as a basis for these findings.