Well-being and Long-term Physical Activity Participation in Midlife Adults: A Latent Class Analysis.

Background: Despite the benefits of physical activity, a large majority of adults fail to get the recommended amount of regular exercise, and interventions to increase physical activity typically achieve only temporary improvements. The potential contribution of positive psychological functioning to the maintenance of physical activity has not been widely examined. Purpose: To test the hypothesis that psychological well-being would increase the likelihood of sustained physical activity in adults using a person-centered approach with longitudinal data. Methods: Participants (N = 2,214) were from the longitudinal Survey of Midlife Development in the United States (MIDUS). Continuous latent variables representing physical activity at three waves of MIDUS were used to partition respondents into distinct (categorical) classes based on longitudinal activity profiles. Results: Latent class analyses identified three distinct physical activity profiles: sustained, consistently low, and declining activity (the normative class). Multinomial logistic regression analyses showed that the odds of membership in the sustained activity class were significantly higher for those with higher eudaimonic well-being (OR = 1.08 [1.03-1.13], p = .001), after adjustment for diverse covariates. Supplemental analyses revealed similar associations for specific subdomains of eudaimonic well-being. Conclusion: This study provides evidence that greater well-being may help sustain physical activity in the long term. These results suggest that improving well-being may be a useful addition to interventions aimed at increasing long-term physical activity participation.

Lighten UP! A community-based group intervention to promote psychological well-being in older adults.

OBJECTIVES: Aging is often characterized by declines in physical and mental health and increased risk for depression and social isolation. A protective factor that has been found to effectively moderate these phenomena is psychological well-being. The aim of his study was to pilot test a novel group intervention (Lighten UP! program) for the promotion of psychological well-being in older adults living in the community. METHODS: Lighten UP! is an eight-week program consisting of 90-minute group session designed to teach participants to identify and savor positive experiences across multiple domains of eudaimonic well-being. It was delivered to a sample of 103 men and women aged 60 or over, that were assessed pre- and post-intervention with Ryff's Psychological Well-being Scale (PWB), Life Satisfaction scale, Geriatric Depression Scale, Symptom Questionnaire, and items measuring sleep complaints and social well-being. RESULTS: At the end of the eight weeks, participants reported significantly increased PWB, life satisfaction, and social well-being along with lower levels of depression and fewer physical symptoms and sleep complaints. These gains were particularly robust for individuals with lower pre-program levels of PWB. CONCLUSIONS: This pilot investigation suggests the feasibility of a short group program for enhancing well-being in older adults. Future controlled investigations with long-term follow-up assessment are needed to confirm the effectiveness and sustained benefits of the Lighten UP!

Self-Rated Health and Mortality: Moderation by Purpose in Life.

Poor self-rated health consistently predicts reduced longevity, even when objective disease conditions and risk factors are considered. Purpose in life is also a reliable predictor of diverse health outcomes, including greater longevity. Given prior work in which we showed that purpose in life moderated the association between chronic conditions and health-related biological factors, the aim of the current study was to examine the role of purpose in life in moderating the relationship between subjective health and mortality. We also examined potential differences in these associations by race/ethnicity. Data were from two large national longitudinal studies-the Health and Retirement Study (HRS) and the Midlife in the United States (MIDUS) study-with a 12- to 14-year follow-up period for mortality estimates. Results of logistic regression analyses showed that purpose in life and self-rated health were both significantly positively associated with longevity, and that purpose in life significantly moderated the relationship between self-rated health and mortality. Stratified analyses showed similar results across all racial/ethnic groups, with the exception of Black MIDUS participants. These results suggest that greater purpose in life may provide a buffer against the greater probability of mortality associated with poor subjective health.

Income, education, and inflammation: differential associations in a national probability sample (The MIDUS study).

OBJECTIVE: To examine the associations between income and education and three markers of inflammation: interleukin-6 (IL-6), C-reactive protein (CRP), and fibrinogen. Socioeconomic status is inversely linked with health outcomes, but the biological processes by which social position "gets under the skin" to affect health are poorly understood. METHOD: Cross-sectional analyses involved participants (n = 704) from the second wave of the national population-based Survey of Midlife Development in the United States (MIDUS). Data on pretax household-adjusted income and educational attainment were collected by questionnaire and telephone interview, respectively. Detailed medical history interviews, inventories of medication, and fasting blood samples for assessment of inflammatory proteins were obtained during an overnight clinic stay. RESULTS: All three inflammatory proteins were inversely associated with both income and education in bivariate analyses. However, multivariate regression models, adjusting for potential confounds, showed that only low income predicted higher levels of inflammatory proteins. Moreover, inclusion of IL-6 in the regression models for CRP and fibrinogen eliminated the associations with income. CONCLUSION: These results suggest that income explains the association between education and peripheral inflammation. In short, the reason that higher education is linked to reduced peripheral inflammation is because it reduces the risk for low income status, which is what is directly associated with reduced peripheral inflammation. The findings also suggest that the links between income and both CRP and fibrinogen are mediated by IL-6. These observations help to sharpen our understanding of the relationship between social position and biological markers of illness in the United States.

The Survey of the Health of Wisconsin (SHOW), a novel infrastructure for population health research: rationale and methods.

BACKGROUND: Evidence-based public health requires the existence of reliable information systems for priority setting and evaluation of interventions. Existing data systems in the United States are either too crude (e.g., vital statistics), rely on administrative data (e.g., Medicare) or, because of their national scope (e.g., NHANES), lack the discriminatory power to assess specific needs and to evaluate community health activities at the state and local level. This manuscript describes the rationale and methods of the Survey of the Health of Wisconsin (SHOW), a novel infrastructure for population health research. METHODS/DESIGN: The program consists of a series of independent annual surveys gathering health-related data on representative samples of state residents and communities. Two-stage cluster sampling is used to select households and recruit approximately 800-1,000 adult participants (21-74 years old) each year. Recruitment and initial interviews are done at the household; additional interviews and physical exams are conducted at permanent or mobile examination centers. Individual survey data include physical, mental, and oral health history, health literacy, demographics, behavioral, lifestyle, occupational, and household characteristics as well as health care access and utilization. The physical exam includes blood pressure, anthropometry, bioimpedance, spirometry, urine collection and blood draws. Serum, plasma, and buffy coats (for DNA extraction) are stored in a biorepository for future studies. Every household is geocoded for linkage with existing contextual data including community level measures of the social and physical environment; local neighborhood characteristics are also recorded using an audit tool. Participants are re-contacted bi-annually by phone for health history updates. DISCUSSION: SHOW generates data to assess health disparities across state communities as well as trends on prevalence of health outcomes and determinants. SHOW also serves as a platform for ancillary epidemiologic studies and for studies to evaluate the effect of community-specific interventions. It addresses key gaps in our current data resources and increases capacity for etiologic, applied and translational population health research. It is hoped that this program will serve as a model to better support evidence-based public health, facilitate intervention evaluation research, and ultimately help improve health throughout the state and nation.

Moderation of the Association Between Chronic Medical Conditions and Functional Limitations Over Time by Physical Activity: Effects of Age.

BACKGROUND: Age-related accumulation of chronic medical conditions increases disability in older adults. Physical activity potently combats chronic conditions and disability. However, it is unclear whether activity maintenance alleviates the effects of chronic conditions on disability and if this buffering effect differs with age. This study examined whether long-term physical activity can forestall functional limitations in the face of accumulating chronic conditions among middle-aged and older adults. METHODS: Participants (n = 2,119; 54.7% female) were from the Survey of Midlife Development in the United States. Self-reported physical activity, number of chronic conditions, and functional limitations were obtained across 18-20 years. Functional limitations were regressed against the change in chronic conditions, physical activity, and their interaction over time in a multilevel model of change. Baseline age was added as an additional moderator. RESULTS: Faster accumulation of chronic conditions [B(SE) = 2.08(0.32), p < .001] and steeper declines in activity [B(SE) = -2.29(0.41), p < .001] were associated with greater increases in functional limitations over time. Among those with faster-than-average increases in conditions, those who maintained activity had a slower progression of functional limitations, compared to those whose activity declined more rapidly [B(SE) = -11.18(3.96), p = .005]. Baseline age moderated the buffering effect of activity maintenance; older adults were protected against functional limitations only when conditions accumulated slowly [B(SE) = 0.23(0.08), p = .005]. CONCLUSION: This study provides evidence for an age-dependent buffering effect of activity maintenance on the longitudinal relationship between chronic conditions and functional limitations. Intervention strategies using physical activity to forestall disability should target midlife adults and consider the rate of condition accumulation.

Childhood maltreatment exposure and physical functional limitations in late adulthood: examining subjective sleep quality in midlife as a mediator.

Objective: The present study had three major aims: 1) To identify sub-groups of adults with differing combinations of childhood maltreatment exposures, 2) to understand the association of childhood maltreatment sub-group membership with subjective sleep quality in midlife, and 3) to assess poor sleep quality in midlife as a mechanism between childhood maltreatment sub-group membership and physical functional limitations in late adulthood. Design: Data come from the Biomarker project of the Midlife Development in the United States study (n = 1251). Outcome measures: The Pittsburgh Sleep Quality Index (Buysse et al., 1989) was used to assess sleep quality in midlife. Functional limitations in late adulthood were measured using a version of the SF-36 (Brazier et al., 1992). Results: Two vulnerable childhood maltreatment sub-groups emerged (Physical and Emotional Maltreatment Sub-group, n = 49, and Sexual Abuse Sub-group, n = 105) and a normative sub-group (n = 1087; low exposure to childhood maltreatment). Poor sleep quality in midlife mediated the association between both maltreatment sub-groups and functional limitations in late adulthood. Conclusion: Results highlight the role of sleep in linking childhood maltreatment with functional impairments in adulthood and offer a potential target for interventions to improve quality of life in older adults.

Individuals' perceptions of social support from family and friends are associated with lower risk of sleep complaints and short sleep duration.

OBJECTIVE: To examine whether individuals' perceptions of social support (SS) from partners, other family members, and friends are associated with risk of sleep complaints and short sleep duration. METHODS: A cross-sectional and prospective study with 1,688 community dwelling adults from the Retirement and Sleep Trajectories study. Four annual, self-administered questionnaires were mailed to participants in the year 2010-2014. Self-reports of individuals' perceptions of SS were obtained at the baseline survey. Sleep quality and duration were self-reported on each of the four surveys over the follow-up. Associations were examined with mixed-effect models, controlling for confounders. RESULTS: In fully adjusted analyses, compared with those reporting low SS from their partner, the risk of reporting more than 1 sleep symptom was significantly lower among those with intermediate (relative risk, RR = 0.68; 95% confidence interval, CI = 0.53-0.87) and high SS (RR = 0.61; 95% CI=0.48-0.77). Similarly, relative to those with low SS, those reporting high SS from family (RR = 0.74; 95% CI = 0.57-0.94) and friends (RR = 0.73; 95% CI = 0.58-0.92) had lower risk of having more than 1 sleep symptom. Compared with those with low, intermediate (RR = 0.70; 95% CI = 0.52-0.96), and high SS (RR = 0.63; 95% CI = 0.48-0.84) from partners, intermediate (RR = 0.76; 95% CI = 0.59-0.97) and high SS (RR = 0.69; 95% CI = 0.51-0.92) from family and high SS (RR = 0.74; 95% CI = 0.56-0.99) from friends were associated with lower risk of short sleep (≤6 h). CONCLUSION: The perception of higher SS from relatives and friends is independently associated with lower risk of poor sleep quality and short sleep duration. Future research and intervention studies should test whether strengthening social relationships can positively effect sleep health.

Sleep duration in the United States: a cross-sectional population-based study.

Sleep duration is associated with cardiovascular disease and diabetes risk factors, depression, automobile and workplace accidents, and prospective mortality. Little is known, however, about sleep patterns in the US population. The 2004-2007 National Health Interview Survey-Sample Adult Files provide nationally representative data for 110,441 noninstitutionalized US adults aged 18 years or older, and multinomial logistic regression examines whether variables in 5 domains-demographic, family structure, socioeconomic, health behavior, and health status-are associated with long or short sleep duration. Being older, non-Hispanic black, or a current or former smoker; having low levels of education, income, or few income sources; consuming few or numerous drinks in a week; or reporting cardiovascular disease, diabetes, depression, underweight, or activity limitations is associated with increased odds of both long and short sleep duration. Other variables are associated with shorter (e.g., living with young children, being unmarried, working long hours, more frequent binge drinking) or longer (e.g., being younger, Mexican American, pregnant, or having low levels of physical activity) sleep hours. The authors identify numerous risk factors for long and short sleep; many of those variables are potential confounders of the relation between sleep hours and other health outcomes.

Chronic discrimination predicts higher circulating levels of E-selectin in a national sample: the MIDUS study.

Chronic discrimination in both minority and non-minority populations is linked to adverse health outcomes, including increased risk of cardiovascular disease and increased mortality, but the biological processes through which discrimination affects health are unclear. The current study tested the hypothesis that discrimination in a sample of Caucasians would predict elevated serum levels of E-selectin, an indication of endothelial dysfunction which itself is associated with atherosclerosis and cardiovascular disease risk. Participants (N=804) in the biomarker sample from the Survey of Midlife in the United States (MIDUS) provided information about experiences of both major and everyday discrimination at two times separated by a 9-10 year interval. The discrimination measures were designed to assess perceived unfair treatment (e.g. being fired unfairly) independently of the perceived reasons for the unfair treatment (e.g. race, gender). Serum E-selectin was measured at the second wave of data collection. Women reported significantly more instances of major (P<0.05) and everyday P<0.001) discrimination than men. Analyses of Covariance (ANCOVA) showed that both greater lifetime exposure to major discrimination (P<0.05) and chronic exposure to everyday discrimination (P<0.05) predicted higher circulating levels of E-selectin, but only in men. These associations remained statistically significant after adjustments for potential confounding variables, including age, race, socioeconomic status, health status, and health behavior. These results highlight a potential biological mechanism by which exposure to unfair treatment may be related to health, particularly cardiovascular function. Moreover, they add to a growing literature suggesting that unfair treatment in general may predict adverse health outcomes.

Multimorbidity, inflammation, and disability: a longitudinal mediational analysis.

BACKGROUND: Using longitudinal data from the Survey of Mid-Life Development in the United States, this study examined the role of systemic inflammation in mediating the link between multimorbidity and increases in and onset of functional limitations over a 17-19 year follow-up period. METHODS: Participants completed questionnaire assessments of chronic conditions and functional limitations. Interleukin-6, C-reactive protein, and fibrinogen were assayed in serum. Structural equation models were used to predict increases in and onset of functional limitations associated with baseline multimorbidity status; mediation by inflammation was also determined. RESULTS: Multimorbidity (versus 0-1 conditions) predicted more functional limitations and greater odds of onset of limitations over time. Significant indirect effects showed that inflammation partially mediated the link between multimorbidity and changes in, but not onset of, limitations. DISCUSSION: These results show that inflammation, a nonspecific marker of multiple disease conditions, explains in part the degree to which multimorbidity is disabling.

Relative sensitivity of cortisol indices to psychosocial and physical health factors.

OBJECTIVE: Regulation of cortisol under resting conditions is widely used to assess physical and psychological status, but due to the diversity of possible assessments (e.g., cumulative levels; diurnal patterns), considering one or a few at a time hampers understanding and interpretation. Moreover, most studies of cortisol regulation focus on negatively-valanced experiences. This study examined the inter-correlations among cortisol indices and their relative contribution to the explained variance in diverse psychosocial and health factors, including positive functioning. METHODS: Data are from midlife and older adults (N = 513; 47.2% male). Cortisol was assessed in urine (overnight) and saliva (at rest and over 4 consecutive days). Positive and negative psychosocial and health factors were assessed by self-report. In addition to examining associations among cortisol indices, relative weight analysis was used to determine which indices were most robustly linked to specific psychosocial factors. RESULTS: Inter-correlations among indices were weak-to-moderate, suggesting that they measure different aspects of hypothalamic-pituitary-axis activity. Overall variance in psychosocial and health factors (R2) explained by the cortisol indices ranged from 0.01 to 0.07. Of this explained variance, relative weight analysis showed that waking cortisol contributed most to the variance in hedonic well-being (32.1%-38.2%), bedtime cortisol to depression-related factors (32.1%-46.9%), the cortisol awakening response to eudaimonic well-being (35.8%-50.5%), cortisol slope to perceived stress (29.2%), and urinary cortisol to physical factors (38.5% and 62.7%). CONCLUSIONS: Positive and negative factors were related to largely non-overlapping cortisol indices. This study illuminates nuanced associations among cortisol indices and diverse aspects of mental and physical health, facilitating thoughtful examination of the complex role of hypothalamic-pituitary-axis activity in health.

The Role of Affect on Physical Health Over Time: A Cross-Lagged Panel Analysis Over 20 Years.

BACKGROUND: While previous studies have investigated the interplay between affect and health (1) over an extended period of time, (2) in a representative population, and (3) while modelling positive and negative affect simultaneously, no single study has done all three at once. METHODS: The present study accomplishes this by sampling adults from the Midlife Development in the US study who completed affect (Mroczek & Kolarz, 1998) and health measures (chronic conditions, Charlson, Szatrowski, Peterson, & Gold, 1994; functional limitations, McHorney, Ware, Lu, & Sherbourne, 1994; self-reported health) measured three times over 20 years. We ran three (one per health metric) random-intercept cross-lagged panel models, where positive and negative affect were modelled simultaneously. RESULTS: Results indicated that positive and negative affect significantly predicted future heath (functional limitations/self-reported health) and that this relationship was reciprocal (i.e. health measures predicted future affect). However, there were no significant cross-lagged relations between affect and chronic conditions. CONCLUSION: Our results suggest that both positive and negative affect play an equal role in predicting future health for functional limitations and self-reported health as well as highlight the bi-directionality of this relationship. Additionally, the degree to which affect predicts future health may be moderated by the type of health outcome.

The Association of Psychological Well-Being with Disablement Processes in a National Sample.

OBJECTIVE: Objectives were to explore subgroups of individuals with differential disability trajectories and evaluate the protective effects of psychological well-being (i.e. hedonic and eudaimonic) in the presence of multiple disease conditions (or multimorbidity) and sociodemographic disadvantages. METHODS: Data come from the prospective longitudinal cohort study the Midlife Development in the United States (n = 3,904). Three waves of data spanning a 20-year period were used to identify subgroups with different disability trajectories. Subgroup membership was then modelled as a function of psychological well-being assessed at wave 1 of the study using multinomial logistic regression. RESULTS: Three unique groups were identified: a normative group with initially low and slowly increasing levels of disability; a group with high levels of disability that was stable over time; and a group with moderate initial levels of disability that increased over time. Hedonic well-being at wave 1 was associated with membership in the risk groups relative to the normative group. CONCLUSION: Individuals may follow one of three disability pathways mostly as a function of multimorbidity. However, hedonic well-being was associated with having an advantageous disability trajectory regardless of multimorbidity status. Cultivating psychological well-being may improve disability outcomes in aging individuals.

Socioeconomic status predicts objective and subjective sleep quality in aging women.

OBJECTIVE: To test the hypothesis that socioeconomic status (SES) would be associated with sleep quality measured objectively, even after controlling for related covariates (health status, psychosocial characteristics). Epidemiological studies linking SES and sleep quality have traditionally relied on self-reported assessments of sleep. METHODS: Ninety-four women, 61 to 90 years of age, participated in this study. SES was determined by pretax household income and years of education. Objective and subjective assessments of sleep quality were obtained using the NightCap sleep system and the Pittsburgh Sleep Quality Index (PSQI), respectively. Health status was determined by subjective health ratings and objective measures of recent and chronic illnesses. Depressive symptoms and neuroticism were quantified using the Center for Epidemiological Studies Depression Scale and the Neuroticism subscale of the NEO Personality Inventory, respectively. RESULTS: Household income significantly predicted sleep latency and sleep efficiency even after adjusting for demographic factors, health status, and psychosocial characteristics. Income also predicted PSQI scores, although this association was significantly attenuated by inclusion of neuroticism in multivariate analyses. Education predicted both sleep latency and sleep efficiency, but the latter association was partially reduced after health status and psychosocial measures were included in analyses. Education predicted PSQI sleep efficiency component scores, but not global scores. CONCLUSIONS: These results suggest that SES is robustly linked to both subjective and objective sleep quality, and that health status and psychosocial characteristics partially explain these associations.

Plasma interleukin-6 and soluble IL-6 receptors are associated with psychological well-being in aging women.

OBJECTIVE: This study tested the hypothesis that psychological well-being would predict lower plasma levels of inflammatory factors in aging women. DESIGN: One hundred thirty-five women ages 61-91 years (M = 74.5 years) participated in this study. After completing self-administered questionnaires in their homes, participants stayed overnight at the General Clinical Research Center (GCRC) at the University of Wisconsin-Madison. Blood samples for cytokine analyses were obtained in participants' homes after the GCRC visit. MAIN OUTCOME MEASURES: Psychological well-being and ill-being, history of health problems, and health behaviors were assessed via self-administered questionnaires. Detailed medical history and concurrent health measures were obtained during the GCRC stay. Enzyme-linked immunosorbent assays were used to determine interleukin-6 (IL-6) and soluble IL-6 receptor (sIL-6R) concentrations in plasma. RESULTS AND CONCLUSION: Regression analyses showed that plasma IL-6 levels were lower in women scoring higher on positive relationships, whereas sIL-6R levels were lower in women scoring higher on purpose in life, even after a variety of sociodemographic and health factors were controlled. These outcomes, combined with the absence of significant links with other measures of well-being and ill-being, suggest selective patterns of association between later life inflammatory processes and psychological factors, particularly those focused on positive ties with others and purposeful engagement.

Self-Reported Sleep Problems Prospectively Increase Risk of Disability: Findings from the Survey of Midlife Development in the United States.

OBJECTIVES: To determine whether subjective poor sleep prospectively increases functional limitations and incident disability in a national sample of adults living in the United States. DESIGN: Prospective cohort. SETTING: Longitudinal Survey of Midlife Development in the United States (MIDUS). PARTICIPANTS: Young, middle-aged, and older men and women (aged 24-75) surveyed in 1995/96 (MIDUS 1) and followed up in 2004-06 (MIDUS 2). Complete data were available for 3,620 respondents. MEASUREMENTS: Data were from telephone interviews and self-administered questionnaires. Participant reported chronic sleep problems within the prior month; functional limitations were assessed using the Functional Status Questionnaire. Demographic (age, sex, race), socioeconomic (educational attainment), health (chronic conditions, depression), and health behavior (obesity, smoking) covariates were assessed to reduce potential confounding. RESULTS: Approximately 11% of the sample reported chronic sleep problems at both MIDUS waves. Average number of activity of daily living (ADL) and instrumental activity of daily living (IADL) limitations increased significantly between MIDUS 1 (ADL limitations: 0.06; IADL limitations: 0.95) and MIDUS 2 (ADL limitations: 0.15; IADL limitations: 1.6; P < .001). Adjusted regression models estimating change in ADL scores showed that chronic sleep problems at MIDUS 1 predicted significantly greater increases in ADL (incident rate ratio (IRR) = 1.55, P < .001) and IADL (IRR = 1.28, P < .001) limitations. In those with no functional limitations at baseline, logistic regression models showed that chronic sleep problems significantly increased the odds of incident ADL (odds ratio (OR) = 2.33, 95% confidence interval (CI) = 1.68-3.24, P < .001) and IADL (OR = 1.70, 95% CI = 1.21-2.42, P = .002) disability. CONCLUSION: Reports of chronic sleep problems predicted greater risk of onset of and increases in functional limitations 9 to 10 years later. Poor sleep may be a robust and independent risk factor for disability in adults of all ages.

Persistent Psychological Well-being Predicts Improved Self-Rated Health Over 9-10 Years: Longitudinal Evidence from MIDUS.

Psychological well-being has been linked with better health, but mostly with cross-sectional evidence. Using MIDUS, a national sample of U.S. adults (N = 4,963), longitudinal profiles of well-being were used to predict in cross-time change over a 9-10 years in self-reported health. Well-being was largely stable, although adults differed in whether they had persistently high versus persistently low or moderate levels of well-being. After adjusting for sociodemographic factors, those with persistently high well-being reported better health (subjective health, chronic conditions, symptoms, functional impairment) across time compared to those with persistently low well-being. Further, persistently high well-being was protective of improved health especially among the educationally disadvantaged. The findings underscore the importance of intervention and educational programs designed to promote well-being for greater segments of society.

Inflammation Partially Mediates the Association of Multimorbidity and Functional Limitations in a National Sample of Middle-Aged and Older Adults: The MIDUS Study.

OBJECTIVE: Older adults are increasingly likely to have two or more chronic medical conditions (multimorbidity) and are consequently at greater risk of disability. Here we examine the role of inflammation in mediating the relationship between multimorbidity and disability. METHOD: Data are from the Survey of Mid-Life in the United States (MIDUS), a national sample of middle-aged and older adults. Structural equation models were used to assess direct relationships between multimorbidity and activities of daily living as well as indirect associations with a latent variable for inflammation (indicated by circulating levels of interleukin-6, C-reactive protein, and fibrinogen) as a mediator. RESULTS: After adjustment for potential confounds, multimorbidity was positively associated with inflammation (p < .001) and functional limitations (p < .001), and inflammation partially mediated the link between multimorbidity and functional limitations (p < .01). DISCUSSION: Inflammation may be an important biological mechanism through which chronic medical conditions are linked to disability in later life.

Environmental stress mediates changes in neuroimmunological interactions.

Combinations of environmental stress coordinately increase toxicological assaults on health, dependent on the genetics of the exposed organism. Multiple gene variances between individuals influence the risks associated with environmental exposures, and environmental stress presents in multiple forms including chemical, physical, and psychological stresses. Combined chemical, physical, and psychological stresses are suggested as exacerbating the initiation and/or duration of illnesses, and many of the detrimental outcomes on health are posited to relate to changes in neuroendocrine immune circuitry. However, most human epidemiological or experimental animal studies have not considered the combination of chemical, physical, and psychological stress on health status. Current consideration is being given to "real world" exposures for assessment of health risk, but this mainly relates to evaluation of chemical mixtures. In addition to concomitant chemical exposures having agonistic and/or antagonistic interactions, the physical and psychological status of the individual can influence exposure outcomes. An individual's psychosocial environment is likely to be important in epidemiological investigations. Neuroimmunology is a burgeoning discipline, and neurotoxicology and immunotoxicology studies should consider the bidirectional regulatory mechanisms between these organ systems and the potential long-term influences of psychological stress. This mini-review discusses some intriguing data from animal and human studies, which address the regulatory pathways between the neural, endocrine, and immune systems, with emphasis on psychological stress.