Maxine Weinstein

Do Chronic Stressors lead to Physiological Dysregulation? Testing the theory of Allostatic Load

Objectives: To explore three questions: 1) Do chronic stressors predict physiological dysregulation? 2) Is that relationship moderated by characteristics of the individual and his or her social environment? and 3) Do perceived levels of stress mediate the relationship between stressors and dysregulation? Methods: Data come from a nationally representative, longitudinal study of older Taiwanese (n = 916). Regression models are used to examine the relationship between the number of life challenges (i.e., stressors) during 1996 to 2000 and physiological dysregulation (in 2000) based on 16 biomarkers that reflect neuroendocrine function, immune system, cardiovascular function, and metabolic pathways. We include interaction terms to test whether psychosocial vulnerability moderates the impact of stressors. Additional models evaluate the mediating effects of perceived stress. Results: We find a positive association between the number of stressors and physiological dysregulation. The results indicate that this relationship is stronger for persons with greater psychosocial vulnerability, but even so, the magnitude of the effect remains modest. We find some evidence that the level of perceived stress mediates the relationship between chronic stressors and physiological dysregulation. Conclusions: Our results provide some support for the theory of allostatic load, although the relationship between life challenges and physiological dysregulation is weak. The evidence also supports the stress-buffering hypothesis: the combination of low social position, weak social networks, and poor coping ability is associated with greater physiological consequences of life challenges. BMI = body mass index; DHEAS = dehydroepiandrosterone sulfate; HDL = high-density lipoprotein; HPA = hypothalamic-pituitary-adrenal; IGF-1 = insulin-like growth factor 1; IL-6 = interleukin-6; SD = standard deviation; SEBAS = Social Environment and Biomarkers of Aging Study; SEI = socioeconomic index; SNS = sympathetic nervous system; UCL = Union Clinical Laboratories.

Social Ties and Perceived Support: Two Dimensions of Social Relationships and Health Among the Elderly in Taiwan

Objectives: Assess the effects of social relationships on physical and mental health among the elderly in Taiwan. Methods: Using 4 waves of a survey of the elderly, we examine the relationship between social ties and perceived support and four health outcomes—mortality, functional status, self-assessed health, and depression. Results:Perceived support and social ties are related to health, but many of the apparent effects are attenuated in the presence of controls for prior health. However, positive perceptions about support are protective of mental (but not physical) health. Discussion: If baseline health is ignored, estimates of the effects of social relationships on health at a given stage of life are likely to be inflated by reverse causality or by effects occurring prior to baseline. Inclusion of controls for initial health reveals that, in general, the relationship between social support and health at the older ages in Taiwan is relatively modest.

A Comparative Analysis of Measurement Approaches for Physiological Dysregulation in an Older Population

The theory of allostatic load describes how the cumulative experience of emotional challenges and stressful events over the life course may take a significant physiological toll on multiple interrelated systems of the body. Various summary measures of these effects have been proposed in the literature, but few studies focus on systematically evaluating them. We use data from a population-based sample of older Taiwanese to compare the explanatory power and cross-sectional predictive performance of several measures of allostatic load for diverse health outcomes. We find that choices regarding which biomarkers to include in a summary measure and how the measure is formed have modest effects across the basic prediction models we evaluate. Our findings suggest that count-based summary measures incorporating risk at both high and low tails and measures that preserve the continuous properties of the biological variables are strategies that may yield stronger predictions of a wider array of health outcomes than other measures. These fundamental insights are useful for researchers in search of empirical formulations of allostatic load and for those who are focused on the development of improved measurement strategies.

The Serotonin Transporter Polymorphism (5-HTTLPR): Allelic Variation and Links with Depressive Symptoms

Background: We compare the genotype distribution for the serotonin transporter polymorphism (5‐HTTLPR) in a sample of older Taiwanese adults with samples of various racial and ethnic groups collected in other studies. We also explore interactions among sex, stressors, and 5‐HTTLPR genotype on depressive symptoms in our sample. Methods: Using a nationally representative sample of 984 Taiwanese aged 53 and older, we model depressive symptoms as a function of 5‐HTTLPR genotype and two classes of stressors: lifetime trauma and recent major life events. We test two‐ and three‐way interactions among stressors, 5‐HTTLPR, and sex. >Results: This sample exhibits higher frequency of S/S and lower frequency of L/L genotype than Western samples, but the distribution is comparable to those in East Asian populations. Nearly 9% carry an allele (XL) that has rarely been reported in the literature. Although the gene–environment (G×E) interaction with recent major life events is not significant, our results suggest that trauma has a worse effect on depressive symptoms for those with S/S or S/L genotype than for those who do not carry the S allele (P<0.05). We find no evidence that this G×E interaction varies by sex. Conclusions: Previous studies of this G×E interaction have been inconclusive, perhaps because interactions between genotype and stressful events are more prominent under extreme stressors. Our findings underscore the need to move beyond a bi‐allelic parameterization of the 5‐HTTLPR polymorphism and raise questions about why East Asian populations exhibit low rates of depression despite a high frequency of the S allele. Depression and Anxiety, 2010.

Sleep duration, sleep quality, and biomarkers of inflammation in a Taiwanese population

PURPOSE Short and long sleep duration and sleep quality are associated with health including all-cause mortality, cardiovascular disease, diabetes, and obesity. Inflammation may play a role in mediating these associations. METHODS We examined associations between inflammation and self-reported sleep characteristics in 1020 respondents of the 2000 and 2006 Social Environment and Biomarkers of Aging Study, a nationally representative survey of Taiwanese adults ages 53 and over. Regression models were used to estimate cross-sectional relationships between inflammation (interleukin-6, C-reactive protein, fibrinogen, e-selectin, soluble intercellular adhesion molecule-1, albumin, and white blood cell count) and a modified Pittsburgh Sleep Quality Index, index subcomponents, and self-reported sleep duration. Change in inflammatory markers between 2000 and 2006 was also used to predict long or short sleep duration in 2006. RESULTS Inflammation was not related to the overall index of sleep quality. However, longer sleep (>8 hr) was associated with higher levels of inflammation. These associations remained after adjustment for waist circumference, self-reported health decline, diabetes, arthritis/rheumatism, heart disease, and depressive symptoms. Increases in inflammation between 2000 and 2006 were associated with long but not short sleep duration in 2006 for several markers. CONCLUSIONS Long sleep duration may be a marker of underlying inflammatory illness in older populations. Future studies should explore whether inflammation explains observed relationships between long sleep and mortality.

A Model of Age-specific Fecundability

A new model of the behavioural and physiological causes of age-specific variation in marital fecundability is presented. Total fecundability is decomposed into a series of susceptibility factors (the length of ovarian cycles, the length of the fertile period within each cycle, the probability that a cycle is ovulatory, and the likelihood that an act of unprotected intercourse within the fertile period results in conception) and an exposure factor reflecting the effect of duration of marriage on coital frequency. The impact of intra-uterine mortality on effective fecundability is also modelled. Data on western women, from which standard age curves of fecundability are estimated, suggest that any decline in fecundity between ages 30 and 40 is attributable to changes, not in the ability to conceive, but in the capacity to carry a pregnancy to term. Sensitivity tests suggest that the most important potential sources of inter-population variation in fecundability are intra-uterine death and the incidence of an...

Social linkages to biological markers of health among the elderly.

The social environment and exposure to life challenge affect a persons physical and emotional well-being. The present research uses a population-based study of the elderly in Taiwan to elaborate the cumulative physiological costs--as reflected in biological markers of risk factors known to have adverse consequences for health--of challenge and unfavourable position in social hierarchies and networks. Overall, biological markers of risk among the elderly are similar in Taiwan and the United States. However, male and female Taiwanese elderly are at lower risk for illness associated with indicators of DHEA-S, while women are at higher risk for illness associated with elevated blood pressure, and men at lower risk for illness associated with total/HDL cholesterol, and glycosylated haemoglobin. There are strong and statistically significant effects of position in social hierarchy (education) and challenge (recent widowhood and a perception of high demands) on an index of cumulative risk (allostatic load). Membership in social networks and participation in social activities have expected, but not statistically discernible, effects.

Measurement of cumulative physiological dysregulation in an older population.

The allostatic load framework postulates that an important pathway connecting the social environment with health involves biological responses to stressful stimuli and the subsequent dysregulation of interrelated physiological systems. We formulate a new measure for cumulative physiological dysregulation using a grade of membership model estimated with biodemographic data from a national sample of older Taiwanese persons. We investigate associations between the measure and physical, psychological, and cognitive function. The results provide insights into the relationships between a set of biological profiles and various health outcomes, identify limitations of earlier approaches, and underscore next steps in the development of improved formulations of physiological dysregulation.

Social environment, life challenge, and health among the elderly in Taiwan.

We use an ongoing longitudinal survey of elderly Taiwanese to examine the linkages among health, the social environment, and exposure to life challenge. Data from three waves of the survey provide measures of social hierarchy, social connection, life challenge, and health outcomes. On the basis of multinomial and binomial logistic models, we explore the effects of social factors and challenge on being unhealthy or deceased at follow-up. The estimates indicate that poor health status at follow-up is associated with (1) low socioeconomic status, not having any living children, limited networks of friends, and low participation in social activities; and (2) three life challenges-chronic financial problems, excessive demands placed by close relatives and friends, and having a spouse in poor health. Respondents facing several challenges or having multiple negative attributes in their social environment are especially likely to be unhealthy at follow-up, although negative attributes appear to be counteracted by positive ones. Many findings from Western societies extend to this Taiwanese population. However, some aspects of social connection and challenge hypothesized to affect health fail to reveal a significant association. The analysis identifies differences between men and women in the effects of specific challenges on health, but sex differences in the effects of socioeconomic status and social connection on health are not significant.

The associations between socioeconomic status, allostatic load and measures of health in older Taiwanese persons: Taiwan social environment and biomarkers of aging study.

Data from a national representative sample of 1023 elderly and near-elderly Taiwanese were used to explore whether allostatic load is associated with health outcomes and mediates the association between socioeconomic status and health in a non-Western population. The information collected included: demographic characteristics; allostatic load scores; socioeconomic status, measured by education and income; health behaviours; health-related variables, including self-rated health, basic activities of daily living difficulties, instrumental activities of daily living difficulties, and physical activity difficulties. The adjusted prevalent odds ratios of higher allostatic load level were 1.25 (95% CI: 1.00, 1.56) for reporting one level worse in self-rated health and 1.43 (95% CI: 1.14, 1.82) for reporting one more physical activity difficulty. There were significant associations of lower education or less income with worse self-rated health and more difficulties with physical functioning. The associations between education, income and health status are not mediated by the conventional ten-point measure of allostatic load in older Taiwanese adults.