Self-efficacy and enjoyment of middle school children performing the progressive aerobic cardiovascular endurance run (PACER).

Self-efficacy and enjoyment were examined among 34 middle school children (M age = 12.5 yr.) performing the Progressive Aerobic Cardiovascular Endurance Run (PACER). Exercise self-efficacy (running) and physical activity enjoyment were measured after viewing a video illustrating the PACER, and subsequently following a PACER test. Significantly greater pre- than post-exercise self-efficacy was reported; enjoyment scores did not differ. Ratings of self-efficacy were higher before exercise than after, but enjoyment scores were not significantly different. A significant correlation was found between post-exercise self-efficacy and enjoyment, but not between pre-exercise self-efficacy and enjoyment. Although positive correlations were found between PACER laps and pre-/post-exercise self-efficacy, correlations with ratings of enjoyment were not significant. Exercise self-efficacy was associated with children's beliefs about the task-specific PACER aerobic exercise; however, exercise enjoyment was stable. Children's self-efficacy and enjoyment beliefs should be considered when developing interventional strategies to promote aerobic exercise participation.

Chronic stress, glucocorticoid receptor resistance, inflammation, and disease risk.

We propose a model wherein chronic stress results in glucocorticoid receptor resistance (GCR) that, in turn, results in failure to down-regulate inflammatory response. Here we test the model in two viral-challenge studies. In study 1, we assessed stressful life events, GCR, and control variables including baseline antibody to the challenge virus, age, body mass index (BMI), season, race, sex, education, and virus type in 276 healthy adult volunteers. The volunteers were subsequently quarantined, exposed to one of two rhinoviruses, and followed for 5 d with nasal washes for viral isolation and assessment of signs/symptoms of a common cold. In study 2, we assessed the same control variables and GCR in 79 subjects who were subsequently exposed to a rhinovirus and monitored at baseline and for 5 d after viral challenge for the production of local (in nasal secretions) proinflammatory cytokines (IL-1ß, TNF-α, and IL-6). Study 1: After covarying the control variables, those with recent exposure to a long-term threatening stressful experience demonstrated GCR; and those with GCR were at higher risk of subsequently developing a cold. Study 2: With the same controls used in study 1, greater GCR predicted the production of more local proinflammatory cytokines among infected subjects. These data provide support for a model suggesting that prolonged stressors result in GCR, which, in turn, interferes with appropriate regulation of inflammation. Because inflammation plays an important role in the onset and progression of a wide range of diseases, this model may have broad implications for understanding the role of stress in health.

Predicted and actual exercise discomfort in middle school children.

PURPOSE: The purpose of this study was to use a match-mismatch paradigm to examine children's exercise discomfort during an aerobic shuttle run. METHODS: Thirty-four middle school females (n = 18) and males (n = 16) aged 11-14 yr participated. An Exercise Discomfort Index (EDI) was calculated as a rating of perceived exertion for the overall body (Children's OMNI Scale) x a rating of perceived muscle hurt (Children's OMNI Muscle Hurt Scale). Measurements were obtained immediately before (i.e., predicted) and after (i.e., actual) performance of the nationally standardized Progressive Aerobic Cardiovascular Endurance Run (PACER) shuttle test of aerobic fitness. Self-report physical activity and sport participation history were obtained before PACER performance. RESULTS: Two-way ANOVA (gender x assessment time point) showed a significant main effect for assessment time point: predicted EDI (means +/- SD = 25.9 +/- 20.1) was greater than actual EDI (means +/- SD = 19.4 +/- 17.8) for the total group (P = 0.021). However, neither the main effect of gender nor the gender x assessment time point interaction was significant. Idiographic analysis showed that overpredictors of discomfort reported less time (5.25 median h x wk(-1)) and engaged in less recreational activity than underpredictors (11.14 median h x wk(-1)). However, no significant relation (P = 0.508) was observed between PACER laps completed and exercise discomfort. CONCLUSIONS: The sample of middle school children in this study predicted greater exercise discomfort than actually experienced when performing a PACER test. It is possible that a discomfort construct plays an important role in the initiation and maintenance of children's aerobic exercise, providing a basis for physical activity interventions.

Trait positive affect and antibody response to hepatitis B vaccination.

Recent evidence suggests that dispositional positive affect may be associated with decreased vulnerability to upper respiratory infections. To explore a potential pathway of this relationship, we examined whether trait positive affect is related to an in vivo immune response relevant for host resistance to infection. Eighty-four healthy, graduate students who tested negative for prior expose to the hepatitis B virus were administered the standard hepatitis B vaccination series. Five months after the first dose, a blood sample was collected for the measurement of specific antibody response to the vaccine and subjects completed a battery of psychosocial questionnaires. Higher scores on a measure of dispositional positive affect were associated with a greater antibody response to hepatitis B vaccination. This relationship occurred after controlling for demographics and body mass and was largely independent of concomitant levels of dispositional negative affect, optimism, and extraversion. In the presence of dispositional positive affect, there was no independent effect of trait negative affect on antibody response. Physical activity played a protective role for individuals low in positive affect, being related to higher antibody responses. These data provide initial evidence that individual differences in dispositional positive affect may be of health significance, being related to an in vivo immune response relevant for protection against infection.

Loneliness, social network size, and immune response to influenza vaccination in college freshmen.

Antibody response to the influenza immunization was investigated in 83 1st-semester healthy university freshmen. Elevated levels of loneliness throughout the semester and small social networks were independently associated with poorer antibody response to 1 component of the vaccine. Those with both high levels of loneliness and a small social network had the lowest antibody response. Loneliness was also associated with greater psychological stress and negative affect, less positive affect, poorer sleep efficiency and quality, and elevations in circulating levels of cortisol. However, only the stress data were consistent with mediation of the loneliness-antibody response relation. None of these variables were associated with social network size, and hence none were potential mediators of the relation between network size and immunization response.

The effect of sunlight on postoperative analgesic medication use: a prospective study of patients undergoing spinal surgery.

OBJECTIVE: Exposure to natural sunlight has been associated with improvement in mood, reduced mortality among patients with cancer, and reduced length of hospitalization for patients who have experienced myocardial infarction. Our aim was to evaluate whether the amount of sunlight in a hospital room modifies a patient's psychosocial health, the quantity of analgesic medication used, and the pain medication cost. METHODS: A prospective study of pain medication use was conducted in 89 patients undergoing elective cervical and lumbar spinal surgery where they were housed on either the "bright" or "dim" side of the same hospital unit. Analgesic medication was converted to standard morphine equivalents for interpatient comparison. The intensity of sunlight in each hospital room was measured daily and psychologic questionnaires were administered on the day after surgery and at discharge. RESULTS: Patients staying on the bright side of the hospital unit were exposed to 46% higher-intensity sunlight on average (p = .005). Patients exposed to an increased intensity of sunlight experienced less perceived stress (p = .035), marginally less pain (p = .058), took 22% less analgesic medication per hour (p = .047), and had 21% less pain medication costs (p = .047). Age quartile was the only other variable found to be a predictor of analgesic use, with a significant negative correlation (p <.001). However, patients housed on the bright side of the hospital consistently used less analgesic medications in all age quartiles. CONCLUSION: The exposure postoperatively of patients who have undergone spinal surgery to increased amounts of natural sunlight during their hospital recovery period may result in decreased stress, pain, analgesic medication use, and pain medication costs.

Psychological stress and antibody response to influenza vaccination: when is the critical period for stress, and how does it get inside the body?

OBJECTIVES: This study attempted to determine whether stress of moderate intensity could modulate the antibody response to an influenza vaccination in healthy young adults, identify critical periods during which stress could influence antibody response, and delineate behavioral and biological pathways that might explain relations between stress and antibody. METHODS: A cohort of 83 healthy young adults underwent 13 days of ambulatory monitoring before, during, and after vaccination. Four times daily, subjects reported the extent to which they felt stressed and overwhelmed and collected a saliva sample that was later used to measure cortisol. A battery of health practices (cigarette smoking, alcohol use, physical activity, sleep hygiene) was assessed daily. Antibody titers to the vaccine components were measured at baseline and at 1-month and 4-month follow-up assessments. RESULTS AND CONCLUSIONS: To the extent that they reported higher levels of stress across the monitoring period, subjects exhibited poorer antibody responses to the New Caledonia strain of the vaccine. Stress ratings on the 2 days before the vaccine and the day it was given were not associated with antibody response. However, the 10 days afterward appeared to be a window of opportunity during which stress could shape the long-term antibody response to varying degrees. With respect to potential mediating pathways, little evidence emerged in favor of cortisol secretion, alcohol consumption, physical activity, or cigarette smoking. However, analyses were consistent with a pattern in which feelings of stress and loss of sleep become locked into a feed-forward circuit that ultimately diminishes the humoral immune response. These findings may shed light on the mechanisms through which stress increase vulnerability to infectious disease.

2002 Robert Ader New Investigator award. Relationship of cardiovascular reactivity, stressful life events, and multiple sclerosis disease activity.

Previous studies of stress in multiple sclerosis patients have suggested that life events may alter the onset and development of MS. However, results have been inconsistent because of infrequent monitoring and reporting bias. We followed fifty female MS patients for 1 year to determine characteristics of life events associated with MS exacerbations, and examine the influence of cardiovascular activity. Subjects completed weekly life-event checklists. The short- and long-term threat of each event was determined using the Life Events and Difficulties Schedule. Neurologic symptoms were also monitored weekly. MS exacerbations were confirmed by a neurologist blinded to psychosocial events. Cardiovascular reactivity to an acute psychological stressor was determined at study onset, and resting heart rate and blood pressure were monitored monthly. Forty-two percent of life events were associated with exacerbations in the subsequent 6 weeks. Logistic regression confirmed that exacerbations were more likely during at-risk periods following life events and were relatively independent of the threat level and type of stressor. Participants with higher cardiovascular reactivity to acute stress and higher baseline heart rate demonstrated a greater number of exacerbations and proportion of weeks ill. Using multiple regression, we found that disability level, medication usage, cardiovascular reactivity, baseline heart rate, and life event density explained approximately 30% of the variance in the proportion of weeks ill. These results are consistent with the hypothesis that stress is a potential trigger of MS disease activity and suggest that autonomic tone and stress reactivity may play a role in the development of stress-related exacerbations.

Stressful life events precede exacerbations of multiple sclerosis.

OBJECTIVE: We longitudinally monitored life events and health changes in patients with multiple sclerosis (MS) to determine whether stressful events may trigger exacerbation of MS. METHODS: Twenty-three women with MS were followed for 1 year. Each subject completed the Psychiatric Epidemiologic Research Interview on a weekly basis. Further information on potentially stressful events was acquired using the Life Events and Difficulties Schedule. Neurologic symptoms were also monitored on a weekly basis throughout the year. Potential MS exacerbations were confirmed by a neurologist who was blind to the presence and timing of stressors. RESULTS: Eighty-five percent of MS exacerbations were associated with stressful life events in the preceding 6 weeks. Stressful life events occurred an average of 14 days before MS exacerbations, compared with 33 days before a randomly selected control date (p < .0001). Survival analysis confirmed that an increase in frequency of life events was associated with greater likelihood of MS exacerbations (hazard ratio = 13.18, p < .05). CONCLUSIONS: These results are consistent with the hypothesis that stress is a potential trigger of disease activity in patients with relapsing-remitting MS.

Reactivity and vulnerability to stress-associated risk for upper respiratory illness.

OBJECTIVE: We tested the hypothesis that the greater a person's laboratory stress-elicited elevation in cortisol, the greater the life stress-related risk for upper respiratory infection (URI). We also tested the prediction that the greater the laboratory stress-elicited rise in natural killer cell (NK) cytotoxicity, the smaller the life stress-related URI risk. Finally, we explored whether sympathetic nervous system (SNS) and enumerative immune reactivities to laboratory stress moderate the relation between life stress and URI. METHODS: At baseline, 115 healthy subjects were administered a negative stressful life events checklist and were tested to assess their SNS (blood pressure, heart rate, and catecholamines), HPA (cortisol), and immune (NK cell cytotoxicity and lymphocyte subsets) reactivities to laboratory speech tasks administered 2 weeks apart. Responses were averaged across the two laboratory assessments to create reactivity scores. After these assessments were completed, participants were followed weekly for 12 consecutive weeks. At each follow-up they completed a measure of perceived stress experienced over the last week. They were also instructed to contact the study coordinator if they had a cold or flu at any time during follow-up. A health care worker verified reported illnesses. RESULTS: In a traditional prospective analysis, high cortisol reactors with high levels of life events had a greater incidence of verified URI than did high reactors with low levels of life events and low reactors irrespective of their life event scores. Using hierarchical linear modeling, CD8(+) number, Natural Killer (NK) cell number, and NK cell cytotoxicity, each interacted with weekly perceived stress levels in predicting concurrent occurrences of self-reported URIs. For these outcomes, low immune reactors were more likely to experience an URI during high stress than low stress weeks. High immune reactors did not exhibit differences in weekly URIs as a function of weekly stress level. The SNS reactivity markers did not moderate the association of stress and URI incidence in either analysis. CONCLUSIONS: Acute HPA and immune responses to laboratory stressors are markers of how vulnerable people are to the increased risk for URI associated with stressors in the natural environment.

The locus coeruleus, Barrington's nucleus, and neural circuits of stress.

Much attention has focused on the role of the locus coeruleus (LC) as a component of the central neural circuitry involved in stress. Many, though not all, stressful stimuli produce activation of LC neurons, as reflected by increased Fos expression in these neurons. Stimulation of the LC elicits many stress-like responses, including increased ACTH secretion, though not all responses to LC stimulation are readily interpretable in the context of stress. In particular, stimulation of the LC, at least in anesthetized rats, elicits a decrease in blood pressure and heart rate. Inhibition of the LC has been reported to inhibit certain responses to stress, including inhibition of ACTH release in response to certain stressors. Furthermore, local inhibition of the LC prevents foot shock-evoked Fos expression in certain brain areas. In the studies of the role of the LC in stress, one complicating factor has been the inadequate attention given to Barrington's nucleus (BN), which is located adjacent to the LC. Although BN is best recognized for its role in the control of micturition, the fact that it is activated by a great variety of stressful stimuli, and that it is anatomically connected to multiple output systems involved in stress responses, suggest that it may play a role in the neural circuitry subserving responses to stress.

Effects of social reorganization on cellular immunity in male cynomolgus monkeys.

Exposure to acute stressors has been shown to impair cellular immunity in human beings and other animal species. Comparatively little is known, however, about the effects of long-term stressors on immune function and how individual behavioral characteristics may mediate differences in immune function and clinical disease susceptibility. To determine the effects of social stress on cellular immunity and reactivation of a latent herpesvirus, 20 Herpes B virus-positive male cynomolgus monkeys were exposed to four periodic reorganizations of social group memberships over 5 months. Observations were made to categorize individuals as high or low in expression of aggressive, fearful, and affiliative behaviors. Complete blood counts, lymphocyte proliferation tests, and natural killer cell cytotoxicity assays were performed immediately before and 4 days after reorganizations. Herpesvirus-specific immunoglobulin G antibody levels were measured, and oral and conjunctival swabs were cultured for virus. Reorganization was associated with increased lymphocyte counts (P = 0.0009) and decreased lymphocyte proliferation in response to phytohemagglutinin (P < 0.005), particularly among monkeys showing high levels of fear (P = 0.0137). High-aggressive monkeys showed lower baseline natural killer cell activity (P = 0.0013) and higher lymphocyte counts (P = 0.013) than low-aggressive monkeys. Herpesvirus antibody titers decreased over time (P < 0.004) and no positive virus cultures were obtained. Measures of cellular immunity and behavior were unrelated to virus-specific antibody titers. These results suggest that repeated exposure to a social stressor alters several measures of cellular immunity, and that some of these changes may be predicted by individual differences in agonistic behavior. In contrast to human studies, the results suggest that some psychological stressors may not cause reactivation of a common herpesvirus in this species. © 1996 Wiley-Liss, Inc.

The relationship of agonistic and affiliative behavior patterns to cellular immune function among cynomolgus monkeys (Macaca fascicularis) living in unstable social groups.

Considerable recent interest has focused on the possibility that behavioral factors may influence immune competence, and hence, potentially, patterns of disease. We report here the relationship between the aggressive and affiliative behavior and the cellular immune responses of 30 adult male cynomolgus monkeys (Macaca fascicularis) living in small (n = 5) social groups whose members were periodically redistributed over 26 months. Animals also were subjected to behavioral observation, allowing them to be categorized as either high or low in aggressiveness and affiliation. At the end of the 26 months, lymphocyte proliferation tests were performed on blood samples from all monkeys, using both concanavalin A (ConA) and phytohemagglutinin (PHA) in concentrations of 1, 5, and 10 ug/ml. Two-by-two (Aggressiveness [high, low] X Affiliation [high, low]) analyses of variance performed on these data showed lymphocyte proliferation in response to both ConA and PHA to be greatest (at 1 ug/ml) among highly affiliative animals, albeit only if they were also low in aggressiveness (ConA: Affiliation x Aggression, P < 0.02; PHA: Affiliation x Aggression, P < 0.03). An additional finding was that natural killer cell activity (at an effector to target ratio of 100:1) was highest among highly affiliative animals, regardless of their aggressiveness (P < 0.05). These results indicate that immune competence may be enhanced among monkeys which, in response to a disrupted social environment, spend large amounts of time in affiliation with other animals. Social status, a phenomenon known to influence many aspects of nonhuman primate physiology, was unassociated with nonspecific lymphocyte blastogenesis or natural killer cell activity in this experiment.