Lisa M. Christian

Stress, age, and immune function: toward a lifespan approach.

Both aging processes and psychological stress affect the immune system: Each can dysregulate immune function with a potentially substantial impact on physical health. Worse, the effects of stress and age are interactive. Psychological stress can both mimic and exacerbate the effects of aging, with older adults often showing greater immunological impairment to stress than younger adults. In addition, stressful experiences very early in life can alter the responsiveness of the nervous system and immune system. We review the unique impact of aging and stress on immune function, followed by evidence of interactions between age and stress. Further, we suggest that prenatal or early life stress may increase the likelihood of maladaptive immune responses to stress in late life. An understanding of the interactive effects of stress and age is critical to efforts to determine underlying mechanisms, clarify the directionality of effects, and develop effective interventions in early and late life.

Stress and wound healing.

Over the past decade it has become clear that stress can significantly slow wound healing: stressors ranging in magnitude and duration impair healing in humans and animals. For example, in humans, the chronic stress of caregiving as well as the relatively brief stress of academic examinations impedes healing. Similarly, restraint stress slows healing in mice. The interactive effects of glucocorticoids (e.g. cortisol and corticosterone) and proinflammatory cytokines [e.g. interleukin-1β (IL-1β), IL-1α, IL-6, IL-8, and tumor necrosis factor-α] are primary physiological mechanisms underlying the stress and healing connection. The effects of stress on healing have important implications in the context of surgery and naturally occurring wounds, particularly among at-risk and chronically ill populations. In research with clinical populations, greater attention to measurement of health behaviors is needed to better separate behavioral versus direct physiological effects of stress on healing. Recent evidence suggests that interventions designed to reduce stress and its concomitants (e.g., exercise, social support) can prevent stress-induced impairments in healing. Moreover, specific physiological mechanisms are associated with certain types of interventions. In future research, an increased focus on mechanisms will help to more clearly elucidate pathways linking stress and healing processes.

Stress, Inflammation, and Yoga Practice

Objective: To address the mechanisms underlying hatha yoga’s potential stress-reduction benefits, we compared inflammatory and endocrine responses of novice and expert yoga practitioners before, during, and after a restorative hatha yoga session, as well as in two control conditions. Stressors before each of the three conditions provided data on the extent to which yoga speeded an individual’s physiological recovery. Methods: A total of 50 healthy women (mean age, 41.32 years; range, 30–65 years), 25 novices and 25 experts, were exposed to each of the conditions (yoga, movement control, and passive-video control) during three separate visits. Results: The yoga session boosted participants’ positive affect compared with the control conditions, but no overall differences in inflammatory or endocrine responses were unique to the yoga session. Importantly, even though novices and experts did not differ on key dimensions, including age, abdominal adiposity, and cardiorespiratory fitness, novices’ serum interleukin (IL)-6 levels were 41% higher than those of experts across sessions, and the odds of a novice having detectable C-reactive protein (CRP) were 4.75 times as high as that of an expert. Differences in stress responses between experts and novices provided one plausible mechanism for their divergent serum IL-6 data; experts produced less lipopolysaccharide-stimulated IL-6 in response to the stressor than novices, and IL-6 promotes CRP production. Conclusion: The ability to minimize inflammatory responses to stressful encounters influences the burden that stressors place on an individual. If yoga dampens or limits stress-related changes, then regular practice could have substantial health benefits. CRC = Clinical Research Center; CRP = C-reactive protein; HR = heart rate; hsCRP = high-sensitivity C-reactive protein; IL = interleukin; LPS = lipopolysaccharide; MASQ = Mood and Anxiety Symptom Questionnaire; PANAS = Positive and Negative Affect Scale; PBLs = peripheral blood leukocytes; sIL-6r = soluble IL-6 receptor; TEWL = transepidermal water loss; TNF = tumor necrosis factor; &OV0312;o2 max = maximum oxygen consumption.

Depressive symptoms are associated with elevated serum proinflammatory cytokines among pregnant women

Psychosocial stress and depressive symptoms are associated with increased risk of negative perinatal outcomes including preterm delivery and gestational hypertension. Inflammation is a likely mechanism by which distress may promote these outcomes. It is well-established that stress and depressive symptoms are associated with elevated serum inflammatory markers in nonpregnant populations. However, the immune system exhibits significant changes during pregnancy. Thus, the extent to which these findings extend to pregnancy is largely unknown. The current study examined associations among perceived stress, depressive symptoms, and serum inflammatory markers in a sample of 60 pregnant women. Fifty seven percent were African-American, 82% had completed high school or less education, and 63% reported an annual family income below

Poorer self-rated health is associated with elevated inflammatory markers among older adults

15,000. Participants completed the Perceived Stress Scale (PSS) and the Center for Epidemiologic Studies Depression Scale (CES-D). Serum levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) were determined using high sensitivity immunoassays. Regression analyses demonstrated that after controlling for pre-pregnancy Body Mass Index (BMI), higher scores on the CES-D were related to significantly higher levels of IL-6 (beta=.23, p=.05) and marginally higher TNF-alpha (beta=.24, p=.06). Perceived stress was not significantly related to serum levels of IL-6 or TNF-alpha. In sum, these results indicate that depressive symptoms are associated with higher levels of maternal serum inflammatory markers during pregnancy. These data are consistent with the contention that depressive symptoms may contribute to negative perinatal outcomes via inflammatory pathways.

Psychoneuroimmunology in pregnancy: immune pathways linking stress with maternal health, adverse birth outcomes, and fetal development.

OBJECTIVE Self-rated health is a strong independent predictor of mortality after accounting for objective health status, behavioral risk factors, and sociodemographic characteristics. However, mechanisms underlying this association are largely unexplained. Inflammation has been associated with increased risk of morbidity and mortality in the elderly. The current study aimed to: (1) examine associations between self-rated health and serum inflammatory markers in older adults; (2) examine the relative strength of these associations for self-rated health versus self-rated change in recent health; (3) examine components of self-rated health that may underlie the association between inflammation and global self-rated health. METHODS Self-rated health, as measured by the RAND health survey, and serum interleukin (IL)-6 and C-reactive protein (CRP) were assessed among 250 generally healthy older adults (185 women, 65 men; average age=63.8±13.7 years). RESULTS A series of linear regression analyses demonstrated that poorer self-rated health was significantly associated with higher IL-6 and CRP. These relationships remained after controlling for age, body mass index, gender, and objective health conditions. These associations also remained after controlling for depressive symptoms, neuroticism, perceived change in health over the past year, and health behaviors (smoking, sleep quality, and physical activity). Analyses of RAND component measures demonstrated that poorer physical functioning was significantly associated with IL-6; the relationship between global self-rated health and both IL-6 and CRP remained after accounting for perceived physical functioning. CONCLUSIONS Poorer self-rated health is associated with elevated serum inflammatory markers among generally healthy older adults. The relationship of self-rated health with inflammatory markers is not secondary to depressive symptoms, neuroticism, or recent changes in perceived health. Subjective ratings of health provide important clinical information regarding inflammatory status, beyond traditional objective risk factors, even among generally healthy individuals.

Longitudinal changes in serum proinflammatory markers across pregnancy and postpartum: Effects of maternal body mass index

It is well-established that psychological stress promotes immune dysregulation in nonpregnant humans and animals. Stress promotes inflammation, impairs antibody responses to vaccination, slows wound healing, and suppresses cell-mediated immune function. Importantly, the immune system changes substantially to support healthy pregnancy, with attenuation of inflammatory responses and impairment of cell-mediated immunity. This adaptation is postulated to protect the fetus from rejection by the maternal immune system. Thus, stress-induced immune dysregulation during pregnancy has unique implications for both maternal and fetal health, particularly preterm birth. However, very limited research has examined stress-immune relationships in pregnancy. The application of psychoneuroimmunology research models to the perinatal period holds great promise for elucidating biological pathways by which stress may affect adverse pregnancy outcomes, maternal health, and fetal development.

Depressive symptoms predict exaggerated inflammatory responses to an in vivo immune challenge among pregnant women.

BACKGROUND The maternal immune system undergoes substantial changes to support healthy pregnancy. Although obesity is a primary driver of inflammation and predictive of perinatal complications, additive effects of pregnancy and obesity on changes in inflammatory processes are not well delineated. METHODS This study examined serum proinflammatory markers interleukin(IL)-6, IL-8, tumor necrosis factor (TNF)-α, IL-1β, and C-reactive protein (CRP) during each trimester of pregnancy and 4-6 weeks postpartum among 57 women. RESULTS Overall, IL-6 showed an increasing trend across pregnancy and significant increase at postpartum. Similarly, TNF-α increased significantly across gestation, with a further increase at postpartum. Both IL-8 and IL-1β showed a U-shaped curve, decreasing from early to later pregnancy, and increasing at postpartum. Finally, serum CRP decreased significantly across pregnancy, with further decreases at postpartum. Maternal obesity predicted higher IL-6 at each study visit. Obese women showed a trend toward elevated serum CRP during pregnancy, and significantly higher levels at postpartum. DISCUSSION The course of pregnancy and postpartum is characterized by significant changes in serum proinflammatory mediators. Obese women show elevations in serum proinflammatory markers relative to normal weight women during pregnancy and postpartum. Further research is needed to determine the extent to which obesity-induced inflammation affects maternal and fetal health.

Maternal Obesity Is Associated with Alterations in the Gut Microbiome in Toddlers

OBJECTIVE Stress and depressive symptoms predict exaggerated inflammatory responses to a biological challenge in nonpregnant humans and animals. The extent to which these findings generalize to pregnancy is unknown because the immune system exhibits substantial changes to support pregnancy. Notably, inflammatory responses to infectious agents play a causal role in the development of gestational hypertension as well as risk for preterm birth. Thus, depressive symptoms may increase susceptibility to these outcomes via sensitization of inflammatory processes. The current study was designed to test the hypothesis that depressive symptoms would predict an exaggerated proinflammatory response to an in vivo antigen challenge, influenza virus vaccination, among pregnant women. METHOD Twenty-two pregnant women completed two study visits: baseline and 1week after receiving influenza virus vaccination. Depressive symptoms were measured with the Center for Epidemiologic Studies Depression Scale (CES-D) at baseline. Serum levels of macrophage migration inhibitory factor (MIF) were determined using a high sensitivity immunoassay at both study visits. OUTCOMES Analyses demonstrated that, as compared to those in the lowest tertile of CES-D scores, those in the highest tertile exhibited significantly higher levels of MIF 1week after influenza virus vaccination (p=.035). CONCLUSIONS Depressive symptoms predicted exaggerated MIF production following influenza virus vaccination during pregnancy. These data support the hypothesis that depressive symptoms are associated with sensitization of the inflammatory response during pregnancy. Thus, women with greater depressive symptoms may be more vulnerable to negative sequelae of infectious illness during pregnancy.

Stress-Induced Inflammatory Responses in Women: Effects of Race and Pregnancy

Children born to obese mothers are at increased risk for obesity, but the mechanisms behind this association are not fully delineated. A novel possible pathway linking maternal and child weight is the transmission of obesogenic microbes from mother to child. The current study examined whether maternal obesity was associated with differences in the composition of the gut microbiome in children in early life. Fecal samples from children 18–27 months of age (n = 77) were analyzed by pyro-tag 16S sequencing. Significant effects of maternal obesity on the composition of the gut microbiome of offspring were observed among dyads of higher socioeconomic status (SES). In the higher SES group (n = 47), children of obese (BMI≥30) versus non-obese mothers clustered on a principle coordinate analysis (PCoA) and exhibited greater homogeneity in the composition of their gut microbiomes as well as greater alpha diversity as indicated by the Shannon Diversity Index, and measures of richness and evenness. Also in the higher SES group, children born to obese versus non-obese mothers had differences in abundances of Faecalibacterium spp., Eubacterium spp., Oscillibacter spp., and Blautia spp. Prior studies have linked some of these bacterial groups to differences in weight and diet. This study provides novel evidence that maternal obesity is associated with differences in the gut microbiome in children in early life, particularly among those of higher SES. Among obese adults, the relative contribution of genetic versus behavioral factors may differ based on SES. Consequently, the extent to which maternal obesity confers measureable changes to the gut microbiome of offspring may differ based on the etiology of maternal obesity. Continued research is needed to examine this question as well as the relevance of the observed differences in gut microbiome composition for weight trajectory over the life course.