Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (71 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2015)

Scientific evidence continues to accumulate that relates the experience of stress with overall poor health. However, defining what is meant by the term ‘stress’, in-order to examine its association with the experience adverse health, has been a difficult task for medical researchers. In the present investigation, using linear mixed effect regression analyses, we were interested in evaluating how the experience of psychosocial stress was related to one conceptualization of ‘stress’ as it impacts the human body, allostatic load. Allostatic load, proposed as ‘the cost of chronic exposure to fluctuating or heightened neural or neuroendocrine response resulting from repeated or chronic environmental challenge that an individual reacts to as being particularly stressful’ has been identified in the medical literature as mechanism that is associated with numerous negative health events, especially with regards to overall worse cardiovascular and immune system health. Our aim was to identify the extent to which a cumulative measure of psychosocial stress was related to allostatic load, as well as, identify the relative contributions of eleven specific dimensions of stress to that relationship. We also evaluated whether and how these relationships were moderated by sociodemographic, health behavior and psychosocial resource characteristics, to better understand how psychosocial stress was related to allostatic load across various sub-populations. Data for the analyses were obtained from the Midlife Development in the United States (MIDUS) study, a national, longitudinal investigation with a purpose to investigate the role of the behavioral, psychological and social factors that account for the age related variations in health and well-being across a national sample of Americans. As presented within the written dissertation, further information is provided for readers as an overall introduction to the dissertation (Chapter 1), additional details regarding our proposed aims (Chapter 2), the background and significance for our line of inquiry (Chapter 3), the analytical methods that were implemented for the purpose of this investigation (Chapter 4), the results and findings from our analyses (Chapter 5), a discussion of the results and findings (Chapter 6) and then a highlight of the main study limitations (Chapter 7) along with our overall study conclusions (Chapter 8).

    Cover page: Relationship between Psychosocial Stress and Allostatic Load: Findings from the MIDUS study
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (1993)
    Identical measures of social ties obtained from three community-based cohorts aged 65 and over from East Boston, MA; New Haven, CT; and two rural counties in Iowa permit the first direct cross-community comparison of the hypothesis that social isolation increases 5-year mortality risks (1982 to 1987) for older men and women. In sex-specific proportional hazards analyses, social ties were significantly and inversely related to mortality independently of age in all three cohorts (e.g., relative hazard (RH) = 1.97 to 3.06 for men and women, comparing those with no ties to those with four types of ties). After controlling for age, pack-years of smoking, body mass, chronic conditions, angina, and physical and cognitive disability, social ties remain significant predictors of mortality risk for the men and women in New Haven (RH = 2.4 and 1.8) and for women in Iowa (RH = 1.9). For the men in Iowa (RH = 1.4) and the men and women in East Boston (RH = 1.0 and 1.3), the associations are weaker and nonsignificant.
      Cover page: Intercommunity variations in the association between social ties and mortality in the elderly A comparative analysis of three communities
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2016)

      Objectives

      The purposes of this study were to compare the relative fit of two alternative factor models of allostatic load (AL) and physiological systems, and to test factor invariance across age and sex.

      Methods

      Data were from the Midlife in the United States II Biomarker Project, a large (n = 1255) multisite study of adults aged 34 to 84 years (56.8% women). Specifically, 23 biomarkers were included, representing seven physiological systems: metabolic lipids, metabolic glucose, blood pressure, parasympathetic nervous system, sympathetic nervous system, hypothalamic-pituitary-adrenal axis, and inflammation. For factor invariance tests, age was categorized into three groups (≤45, 45-60, and >60 years).

      Results

      A bifactor model where biomarkers simultaneously load onto a common AL factor and seven unique system-specific factors provided the best fit to the biomarker data (comparative fit index = 0.967, root mean square error of approximation = 0.043, standardized root mean square residual = 0.028). Results from the bifactor model were consistent with invariance across age groups and sex.

      Conclusions

      These results support the theory that represents and operationalizes AL as multisystem physiological dysregulation and operationalizing AL as the shared variance across biomarkers. Results also demonstrate that in addition to the variance in biomarkers accounted for by AL, individual physiological systems account for unique variance in system-specific biomarkers. A bifactor model allows researchers greater precision to examine both AL and the unique effects of specific systems.
        Cover page: Modeling Multisystem Physiological Dysregulation
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2015)

        Background

        Short sleep and poor sleep quality are associated with risk of cardiovascular disease, diabetes, cancer, and mortality. This study examines the contribution of sleep duration and sleep quality on a multisystem biological risk index that is known to be associated with morbidity and mortality.

        Methods

        Analyses include a population-based sample from the Midlife Development in the United States survey recruited to the Biomarker substudy. A total of 1,023 participants aged 54.5 years (SD = 11.8), 56% female and 77.6% white, were included in the analyses. A multisystem biological risk index was derived from 22 biomarkers capturing cardiovascular, immune, lipid-metabolic, glucose-metabolic, sympathetic, parasympathetic, and hypothalamic-pituitary-adrenal systems. Self-reported average sleep duration was categorized as short (<5 hrs), below normal (5 to <6.5 hrs), normal (6.5 to <8.5 hrs), and long sleepers (8.5+ hrs). Sleep quality was determined using the Pittsburgh Sleep Quality Index categorized as normal (≤5) and poor quality (>5) sleep.

        Findings

        Linear mixed effect models adjusting for age, gender, race, education, income, BMI, and health status were performed. As compared to normal sleepers, multisystem biological risk in both short (B(SE) = .38(.15), p<.01) and long sleepers (B(SE) = .28(.11), p<.01) were elevated. Poor quality sleep alone was associated with elevated multisystem biological risk (B(SE) = .15(.06), p = .01), but was not significant after adjustment for health status. All short sleepers reported poor sleep quality. However in the long sleepers, only those who reported poor sleep quality exhibited elevated multisystem biological risk (B(SE) = .93(.3), p = .002).

        Conclusions

        Self-reported poor sleep quality with either short or long sleep duration is associated with dysregulation in physiological set points across regulatory systems, leading to elevated multisystem biological risk. Physicians should inquire about sleep health in the assessment of lifestyle factors related to disease risk, with evidence that healthy sleep is associated with lower multisystem biological risk.
          Cover page: Sleep and Multisystem Biological Risk: A Population-Based Study
          • Article
          • Peer Reviewed
          UCLA Previously Published Works (2015)
          We examined the joint contributions of self-reported adverse childhood experiences (ACEs) and recent life events (RLEs) to inflammation at midlife, by testing 3 competing theoretical models: stress generation, stress accumulation, and early life stress sensitization. We aimed to identify potential mediators between adversity and inflammation. Participants were 1,180 middle-aged and older adults from the Midlife in the United States (MIDUS) Biomarker Project (M age = 57.3 years, SD = 11.5; 56% female). A composite measure of inflammation was derived from 5 biomarkers: serum levels of C-reactive protein, interleukin-6, fibrinogen, E-selectin, and ICAM-1. Participants provided self-report data regarding ACEs, RLEs, current lifestyle indices (cigarette smoking, alcohol consumption, physical exercise, waist circumference), current depressive symptoms, and demographic/biomedical characteristics. We also used indices of hypothalamic-pituitary-adrenocortical outflow (12-hr urinary cortisol) and sympathetic nervous system output (12-hr urinary norepinephrine and epinephrine). Analyses indicated that ACEs and RLEs were independently associated with higher levels of inflammation, controlling for each other's effects. Their interaction was not significant. The results were consistent with the hypothesis that associations between ACEs and inflammation were mediated through higher urinary norepinephrine output, greater waist circumference, smoking, and lower levels of exercise, whereas higher waist circumference and more smoking partially mediated the association between RLEs and inflammation. In support of the stress accumulation model, ACEs and RLEs had unique and additive contributions to inflammation at midlife, with no evidence of synergistic effects. Results also suggested that norepinephrine output and lifestyle indices may help explain how prior stressors foster inflammation at midlife.
            Cover page: Additive Contributions of Childhood Adversity and Recent Stressors to Inflammation at Midlife: Findings From the MIDUS Study
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2018)

            Objective

            Social disadvantage is associated with markers of physiological dysregulation, which is linked to disease trajectories. Chronic experiences with discrimination are thought to result in the accumulation of physiological "wear and tear" known as allostatic load (AL) among socially marginalized populations such as sexual minorities. Using a nationally representative US sample, we examined whether (1) people who self-identified as homosexual or bisexual display higher levels of AL than heterosexual individuals and (2) subgroups of sexual identity would further differ from each other as a consequence of distinct experiences of marginalization.

            Methods

            We use data from the 2001-2010 National Health and Nutrition Examination Survey. Employing multivariate regression methods with sex-specific analyses, we examined AL score differences among lesbian/gay (n = 211), bisexual (n = 307), homosexually experienced (n = 424), and exclusively heterosexual (n = 12,969) individuals, adjusting for possible confounding due to demographics, health indicators, and, among men, HIV infection status.

            Results

            Results indicate that elevated AL was more common in bisexual men compared with exclusively heterosexual men (adjusted β = 0.25, 95% confidence interval [CI] = 0.05 to 0.44), with significantly higher levels of glycosylated hemoglobin A1c (adjusted odd ratio = 3.51, 95% CI = 1.46-7.92) and systolic blood pressure (adjusted odd ratio = 2.07, 95% CI = 1.02 to 4.18). Gay-identified men evidenced significantly lower AL (adjusted β = -0.22, 95% CI = -0.41 to -0.04). No significant differences in AL were observed among women.

            Conclusions

            These findings indicate that physiological dysregulation is more common in bisexual males compared with all other men. The results are discussed with regard to differences in health outcomes between individuals with different sexual orientations.
              Cover page: Chronic Physiologic Effects of Stress Among Lesbian, Gay, and Bisexual Adults
              • Article
              • Peer Reviewed
              UCLA Previously Published Works (2017)

              Study objectives

              Variable daily sleep (ie, higher intraindividual variability; IIV) is associated with negative health consequences, but potential physiological mechanisms are poorly understood. This study examined how the IIV of sleep timing, duration, and quality is associated with physiological dysregulation, with diurnal cortisol trajectories as a proximal outcome and allostatic load (AL) as a multisystem distal outcome.

              Methods

              Participants are 436 adults (Mage ± standard deviation = 54.1 ± 11.7, 60.3% women) from the Midlife in the United States study. Sleep was objectively assessed using 7-day actigraphy. Diurnal cortisol was measured via saliva samples (four/day for 4 consecutive days). AL was measured using 23 biomarkers from seven systems (inflammatory, hypothalamic-pituitary-adrenal axis, metabolic glucose and lipid, cardiovascular, parasympathetic, sympathetic) using a validated bifactor model. Linear and quadratic effects of sleep IIV were estimated using a validated Bayesian model.

              Results

              Controlling for covariates, more variable sleep timing (p = .04 for risetime, p = .097 for bedtime) and total sleep time (TST; p = .02), but not mean sleep variables, were associated with flatter cortisol diurnal slope. More variable sleep onset latency and wake after sleep onset, later average bedtime, and shorter TST were associated with higher AL adjusting for age and sex (p-values < .05); after controlling for all covariates, however, only later mean bedtime remained significantly associated with higher AL (p = .04).

              Conclusions

              In a community sample of adults, more variable sleep patterns were associated with blunted diurnal cortisol trajectories but not with higher multisystem physiological dysregulation. The associations between sleep IIV and overall health are likely complex, including multiple biopsychosocial determinants and require further investigation.
                Cover page: Sleep and Physiological Dysregulation: A Closer Look at Sleep Intraindividual Variability
                • Article
                On-Line Working Paper Series (2006)

                Single nucleotide polymorphism (SNP) genotype frequencies were examined to determine whether variation in 6 estrogen-related genes was associated with differences in cognitive functioning in women at midlife. DNA from a multiracial/multiethnic sample of 875 African American, Caucasian, Chinese, and Japanese women aged 45 to 56 years participating in the Study of Women’s Health Across the Nation (SWAN) was genotyped. Gene markers from the sex steroid hormone pathway were linked to measures of cognitive functioning including the Digit Span Backward Test (DSB), a measure of working memory; the Symbol Digit Modalities Test (SDMT), a measure of perceptual speed; and the East Boston Memory Test (EBMT), a measure of episodic memory. Statistical models were fit using logistic regression and general linear models to estimate the strength of association of estrogen-related polymorphisms with DSB, SDMT, and EBMT scores. On the EBMT, African American women and Caucasian women with ESR1 rs9340799 GG genotypes had about 1.5 to 2.0 times greater odds of remembering story elements on the EBMT-immediate recall test. Caucasian women with ESR1 rs2234693 CC genotypes had 1.3 to 1.5 times greater odds of remembering story elements on the EBMTdelayed recall test. Chinese women with 17HSD rs615942 GG genotypes, 17HSD rs592389 TT genotypes, and 17HSD rs2830 GG genotypes had about 1.7 times greater odds of remembering story elements on the EBMT-immediate recall test. African American women with CYP 19 rs936306 CC genotypes had about 0.25 to 0.40 lower odds of remembering story elements on the EBMT-immediate recall test, whereas Chinese women with CYP 19 rs936306 CC genotypes had about 2.3 times greater odds of remembering story elements on both the EBMT-immediate and -delayed recall tests. On the DSB, African American women with CYP 19 rs749292 GG genotype had a higher mean score. On the SDMT, Japanese women with ESR1 rs728524 GG genotypes had a higher mean score. On the 3 tests of cognitive functioning, there was 1 significant finding for CYP1A1 and none for the YP1B1 or ESR2 SNPs. We conclude that selected genes involved in estrogen synthesis and metabolism may be associated with performance differences on cognitive function tests. Also, the relevant estrogen-related polymorphisms may vary by race/ethnicity.

                  Cover page: Cognitive Functioning and Sex Steriod Hormone Gene Polymorphisms in Women at Midlife
                  • Article
                  • Peer Reviewed
                  UCLA Previously Published Works (2014)
                  We examined whether long-term fluid cognitive decline was associated with memory problems in everyday life, and whether stress plays a moderating role. We expected that the association between cognitive decline and everyday memory problems would be magnified in the context of self-reported and physiological stress. Data are from the Boston Longitudinal Study, a subsample of the Midlife in the United States study. Participants in the current study (n = 112) completed a battery of tests measuring fluid cognitive functioning at Time 1 (T1) and 2 (T2) over 10 years. At T2, participants completed weekly diaries of self-reported daily stressors and everyday memory problems for 12 consecutive weeks. Also at T2, participants provided 4 saliva samples over the course of 1 day to assess physiological stress using diurnal cortisol profiles [cortisol awakening response (CAR) and diurnal cortisol slope (DCS)]. Self-reported daily stressors and a less healthy DCS were associated with more everyday memory problems, and participants with greater cognitive decline reported more memory problems compared to those with less or no decline. Self-reported daily stressors and CAR moderated the relationship of cognitive decline and memory problems. As expected, more cognitive decline was associated with greater increases in memory problems on weeks when individuals reported more daily stressors and for individuals with a less healthy CAR. The current findings can inform interventions aimed to identify factors, such as daily stress, that contribute to daily functioning in the context of cognitive decline.
                    Cover page: Daily Stress Magnifies the Association Between Cognitive Decline and Everyday Memory Problems: An Integration of Longitudinal and Diary Methods
                    • Article
                    • Peer Reviewed
                    UCLA Previously Published Works (2020)

                    Background

                    Anhedonia, or loss of interest or pleasure, is a feature of depression and transdiagnostic construct in psychopathology. Theory and compelling evidence from preclinical models implicates stress-induced inflammation as a psychobiological pathway to anhedonic behavior; however, this pathway has not been tested in human models. Further, although anhedonia may reflect dysregulation in multiple dimensions of reward, the extent to which stress-induced inflammation alters these dimensions is unclear. Thus, the current experimental study used a standardized laboratory stressor task to elicit an inflammatory response and evaluate effects of stress-induced inflammation on multiple behavioral indices of reward processing.

                    Methods

                    Healthy young women (age 18-25) completed behavioral reward tasks assessing reward learning, motivation, and sensitivity and were randomized to undergo an acute psychosocial stressor (n = 37) or a no-stress active control (n = 17). Tasks were re-administered 90-120 min post-stress to coincide with the peak of the stress-induced inflammatory response. Blood samples were collected for assessment of the pro-inflammatory cytokine interleukin-6 (IL-6) at baseline and 90 and 120 min post stressor.

                    Results

                    Stress-induced IL-6 was associated with increased response bias during reward learning and increased motivation when probability of receiving a reward was low. Sensitivity to reward in the context of a motivation task was not altered in association with stress-induced IL-6.

                    Conclusions

                    Contrary to hypotheses, mild increases in IL-6 following acute stress were associated with increased reward responsiveness during reward learning and selective increases in motivation. Results contribute to an emerging and nuanced literature linking inflammation to reward processing, and demonstrate that behavioral effects of stress-induced inflammation may be detected in the laboratory setting.

                    Clinical trial registration

                    NCT03828604.
                      Cover page: Effects of stress-induced inflammation on reward processing in healthy young women.
                      Top