Social stratification and allostatic load: shapes of health differences in the MIDUS study in the United States.

Social stratification is an important mechanism of human organization that helps to explain health differences between demographic groups commonly associated with socioeconomic gradients. Individuals, or group of individuals, with similar health profiles may have had different stratification experiences. This is particularly true as social stratification is a significant non-measurable source of systematic unobservable differences in both SES indicators and health statuses of disadvantage. The goal of the present study was to expand the bulk of research that has traditionally treated socioeconomic and demographic characteristics as independent, additive influences on health by examining data from the United States. It is hypothesized that variation in an index of multi-system physiological dysregulation - allostatic load - is associated with social differentiation factors, sorting individuals with similar demographic and socioeconomic characteristics into mutually exclusive econo-demographic classes. The data were from the Longitudinal and Biomarker samples of the national Study of Midlife Development in the US (MIDUS) conducted in 1995 and 2004/2006. Latent class analyses and regression analyses revealed that physiological dysregulation linked to socioeconomic variation among black people, females and older adults are associated with forces of stratification that confound socioeconomic and demographic indicators. In the United States, racial stratification of health is intrinsically related to the degree to which black people in general, and black females in particular, as a group, share an isolated status in society. Findings present evidence that disparities in health emerge from group-differentiation processes to the degree that individuals are distinctly exposed to the ecological, political, social, economic and historical contexts in which social stratification is ingrained. Given that health policies and programmes emanate from said legal and political environments, interventions should target the structural conditions that expose different subgroups to different stress risks in the first place.

Hyperkyphosis, kyphosis progression, and risk of non-spine fractures in older community dwelling women: the study of osteoporotic fractures (SOF).

While accentuated kyphosis is associated with osteoporosis, it is unknown whether it increases risk of future fractures, independent of bone mineral density (BMD) and vertebral fractures. We examined the associations of baseline Cobb angle kyphosis and 15 year change in kyphosis with incident non-spine fractures using data from the Study of Osteoporotic Fractures. A total of 994 predominantly white women, aged 65 or older, were randomly sampled from 9704 original participants to have repeated Cobb angle measurements of kyphosis measured from lateral spine radiographs at baseline and an average of 15 years later. Non-spine fractures, confirmed by radiographic report, were assessed every 4 months for up to 21.3 years. Compared with women in the lower three quartiles of kyphosis, women with kyphosis greater than 53° (top quartile) had a 50% increased risk of non-spine fracture (95% CI, 1.10-2.06 after adjusting for BMD, prevalent vertebral fractures, prior history of fractures, and other fracture risk factors. Cobb angle kyphosis progressed an average of 7° (SD = 6.8) over 15 years. Per 1 SD increase in kyphosis change, there was a multivariable adjusted 28% increased risk of fracture (95% CI, 1.06-1.55) that was attenuated by further adjustment for baseline BMD (HR per SD increase in kyphosis change, 1.19; 95% CI 0.99-1.44). Greater kyphosis is associated with an elevated non-spine fracture risk independent of traditional fracture risk factors in older women. Furthermore, worsening kyphosis is also associated with increased fracture risk that is partially mediated by low baseline BMD that itself is a risk factor for kyphosis progression. These results suggest that randomized controlled fracture intervention trials should consider implementing kyphosis measures to the following: (1) further study kyphosis and kyphosis change as an additional fracture risk factor; and (2) test whether therapies may improve or delay its progression.

Kyphosis and paraspinal muscle composition in older men: a cross-sectional study for the Osteoporotic Fractures in Men (MrOS) research group.

BACKGROUND: The prevalence of hyperkyphosis is increased in older men; however, risk factors other than age and vertebral fractures are not well established. We previously reported that poor paraspinal muscle composition contributes to more severe kyphosis in a cohort of both older men and women. METHODS: To specifically evaluate this association in older men, we conducted a cross-sectional study to evaluate the association of paraspinal muscle composition and degree of thoracic kyphosis in an analytic cohort of 475 randomly selected participants from the Osteoporotic Fractures in Men (MrOS) study with baseline abdominal quantitative computed tomography (QCT) scans and plain thoracic radiographs. Baseline abdominal QCT scans were used to obtain abdominal body composition measurements of paraspinal muscle and adipose tissue distribution. Supine lateral spine radiographs were used to measure Cobb angle of kyphosis. We examined the linear association of muscle volume, fat volume and kyphosis using loess plots. Multivariate linear models were used to investigate the association between muscle and kyphosis using total muscle volume, as well as individual components of the total muscle volume, including adipose and muscle compartments alone, controlling for age, height, vertebral fractures, and total hip bone mineral density (BMD). We examined these associations among those with no prevalent vertebral fracture and those with BMI < 30 kg/m2. RESULTS: Among men in the analytic cohort, means (SD) were 74 (SD = 5.9) years for age, and 37.5 (SD = 11.9) degrees for Cobb angle of kyphosis. Men in the lowest tertile of total paraspinal muscle volume had greater mean Cobb angle than men in the highest tertile, although test of linear trend across tertiles did not reach statistical significance. Neither lower paraspinal skeletal muscle volume (p-trend = 0.08), or IMAT (p-trend = 0.96) was associated with greater kyphosis. Results were similar among those with no prevalent vertebral fractures. However, among men with BMI < 30 kg/m2, those in the lowest tertile of paraspinal muscle volume had greater adjusted mean kyphosis (40.0, 95% CI: 37.8 - 42.1) compared to the highest tertile (36.3, 95% CI: 34.2 - 38.4). CONCLUSIONS: These results suggest that differences in body composition may potentially influence kyphosis.

Insulin resistance and bone strength: findings from the study of midlife in the United States.

Although several studies have noted increased fracture risk in individuals with type 2 diabetes mellitus (T2DM), the pathophysiologic mechanisms underlying this association are not known. We hypothesize that insulin resistance (the key pathology in T2DM) negatively influences bone remodeling and leads to reduced bone strength. Data for this study came from 717 participants in the Biomarker Project of the Midlife in the United States Study (MIDUS II). The homeostasis model assessment of insulin resistance (HOMA-IR) was calculated from fasting morning blood glucose and insulin levels. Projected 2D (areal) bone mineral density (BMD) was measured in the lumbar spine and left hip using dual-energy X-ray absorptiometry (DXA). Femoral neck axis length and width were measured from the hip DXA scans, and combined with BMD and body weight and height to create composite indices of femoral neck strength relative to load in three different failure modes: compression, bending, and impact. We used multiple linear regressions to examine the relationship between HOMA-IR and bone strength, adjusted for age, gender, race/ethnicity, menopausal transition stage (in women), and study site. Greater HOMA-IR was associated with lower values of all three composite indices of femoral neck strength relative to load, but was not associated with BMD in the femoral neck. Every doubling of HOMA-IR was associated with a 0.34 to 0.40 SD decrement in the strength indices (p<0.001). On their own, higher levels of fasting insulin (but not of glucose) were independently associated with lower bone strength. Our study confirms that greater insulin resistance is related to lower femoral neck strength relative to load. Further, we note that hyperinsulinemia, rather than hyperglycemia, underlies this relationship. Although cross-sectional associations do not prove causality, our findings do suggest that insulin resistance and in particular, hyperinsulinemia, may negatively affect bone strength relative to load.

Biological correlates of adult cognition: midlife in the United States (MIDUS).

Multiple biological processes are related to cognitive impairment in older adults, but their combined impact on cognition in midlife is not known. Using an array of measurements across key regulatory physiological systems and a state-of-the-art cognition battery that is sensitive to early changes, in a large, national sample of middle-aged and older adults, we examined the associations of individual biological systems and a combined, multi-system index, allostatic load, with cognitive performance. Allostatic load was strongly inversely associated with performance in both episodic memory and executive function. Of 7 biological systems, only the cardiovascular system was associated inversely with both; inflammation was associated inversely with episodic memory only, and glucose metabolism with executive function only. The associations of allostatic load with cognition were not different by age, suggesting that the implications of high allostatic load on cognitive functioning are not restricted to older adults. Findings suggest that a multi-system score, like allostatic load, may assist in the early identification of adults at increased risk for cognitive impairment.

Social strain and executive function across the lifespan: the dark (and light) sides of social engagement.

We investigated how the association between social strain and cognitive efficiency varies with task demands across adulthood, from latencies on simpler speeded tasks to tests involving executive function. Participants (N = 3280) were drawn from the MIDUS survey, a large, diverse national sample of adults who completed cognitive tests including speeded task-switching (Tun & Lachman, 2008, Developmental Psychology, 44, 1421). After controlling for demographic and health variables, we found that higher levels of reported social strain were associated with slower processing speed, particularly for the complex task-switching test relative to simpler speeded tests. Effects of strain were greatest for those with the lowest general cognitive ability. Moreover, those with very high levels of social strain but low levels of social support gave the poorest task-switching performance. These findings provide further evidence for the complex relationship between the social environment and cognition across adulthood, particularly the association between efficiency of executive functions and negative social interactions.

Histories of social engagement and adult cognition: midlife in the U.S. study.

OBJECTIVES: To evaluate whether social contacts, support, and social strain/conflict are related to executive function and memory abilities in middle-age and older adults. METHODS: Longitudinal data on social contacts, support, and strain/conflict were examined in relation to executive function and memory at ages 35-85 years using data from the national Midlife in the U.S. (MIDUS) study. Age-related differences in patterns of association were also examined. RESULTS: Regression analyses, controlling for age, sex, race, education, chronic health conditions, and health behaviors, revealed significant positive associations between histories of greater social contacts and support and both executive function and episodic memory, whereas declines in social contacts were negatively associated with both outcomes. Greater average reported frequency of social exchanges characterized by strain or conflict was negatively associated with executive function but not episodic memory. Patterns were generally consistent across different age groups; where differences were seen, associations were stronger in younger age group. DISCUSSION: Positive and negative aspects of social relationships are related to cognition throughout adulthood, consistent with the hypothesis that social factors have life-long influences on cognition. Positive and negative aspects of social engagement may thus be important factors to consider in relation to efforts to promote optimal cognitive development and cognitive aging.

Depressive symptoms, chronic diseases, and physical disabilities as predictors of cognitive functioning trajectories in older Americans.

OBJECTIVES: To determine the concurrent influence of depressive symptoms, medical conditions, and disabilities in activities of daily living (ADLs) on rates of decline in cognitive function of older Americans. DESIGN: Prospective cohort. SETTING: National population based. PARTICIPANTS: A national sample of 6,476 adults born before 1924. MEASUREMENTS: Differences in cognitive function trajectories were determined according to prevalence and incidence of depressive symptoms, chronic diseases, and ADL disabilities. Cognitive performance was tested five times between 1993 and 2002 using a multifaceted inventory examined as a global measure (range 0-35, standard deviation (SD) 6.0) and word recall (range 0-20, SD 3.8) analyzed separately. RESULTS: Baseline prevalence of depressive symptoms, stroke, and ADL limitations were independently and strongly associated with lower baseline cognition scores but did not predict future cognitive decline. Each incident depressive symptom was independently associated with a 0.06-point lower (95% confidence interval (CI)=0.02-0.10) recall score, incident stroke with a 0.59-point lower total score (95% CI=0.20-0.98), each new basic ADL limitation with a 0.07-point lower recall score (95% CI=0.01-0.14) and a 0.16-point lower total score (95% CI=0.07-0.25), and each incident instrumental ADL limitation with a 0.20-point lower recall score (95% CI=0.10-0.30) and a 0.52-point lower total score (95% CI=0.37-0.67). CONCLUSION: Prevalent and incident depressive symptoms, stroke, and ADL disabilities contribute independently to poorer cognitive functioning in older Americans but do not appear to influence rates of future cognitive decline. Prevention, early identification, and aggressive treatment of these conditions may ameliorate the burdens of cognitive impairment.

Trajectories of cognitive function in late life in the United States: demographic and socioeconomic predictors.

This study used mixed-effects modeling of data from a national sample of 6,476 US adults born before 1924, who were tested 5 times between 1993 and 2002 on word recall, serial 7's, and other mental status items to determine demographic and socioeconomic predictors of trajectories of cognitive function in older Americans. Mean decline with aging in total cognition score (range, 0-35; standard deviation, 6.00) was 4.1 (0.68 standard deviations) per decade (95% confidence interval: 3.8, 4.4) and in recall score (range, 0-20; standard deviation, 3.84) was 2.3 (0.60 standard deviations) per decade (95% confidence interval: 2.1, 2.5). Older cohorts (compared with younger cohorts), women (compared with men), widows/widowers, and those never married (both compared with married individuals) declined faster, and non-Hispanic blacks (compared with non-Hispanic whites) and those in the bottom income quintile (compared with the top quintile) declined slower. Race and income differences in rates of decline were not sufficient to offset larger differences in baseline cognition scores. Educational level was not associated with rate of decline in cognition scores. The authors concluded that ethnic and socioeconomic disparities in cognitive function in older Americans arise primarily from differences in peak cognitive performance achieved earlier in the life course and less from declines in later life.

A multilevel analysis of urban neighborhood socioeconomic disadvantage and health in late life.

The associations between neighborhood context and various indicators of health are receiving growing empirical attention, but much of this research is regionally circumscribed or assumes similar effects across the life course. This study utilizes a U.S. national sample to investigate the association between urban neighborhood socioeconomic disadvantage and health specifically among older adults. Data are from 3442 participants aged 70 years and older in the 1993 Asset and Health Dynamics Among the Oldest Old (AHEAD) Study, and the 1990 U.S. Census. Our approach underscores the importance of multiple dimensions of health (self-reported physician-diagnosed cardiovascular disease [CVD], functional status, and self-rated health) as well as multiple dimensions of neighborhood disadvantage, which are conceptualized as environmental hazards that may lead to a physiologically consequential stress response. We find that individual-level factors attenuate the association between neighborhood disadvantage and both CVD and functional status, but not self-rated health. Net of covariates, high neighborhood socioeconomic disadvantage is significantly associated with reporting poor health. In late life, neighborhood socioeconomic disadvantage is more consequential to subjective appraisals of health than diagnosed CVD or functional limitations.

Urban neighborhoods and depressive symptoms among older adults.

OBJECTIVE: This study seeks to determine whether depressive symptoms among older persons systematically vary across urban neighborhoods such that experiencing more symptoms is associated with low socioeconomic status (SES), high concentrations of ethnic minorities, low residential stability and low proportion aged 65 years and older. METHODS: Survey data are from the Study of Assets and Health Dynamics Among the Oldest Old (AHEAD), a 1993 U.S. national probability sample of noninstitutionalized persons born in 1923 or earlier (i.e. people aged 70 or older). Neighborhood data are from the 1990 Census at the tract level. Hierarchical linear regression is used to estimate multilevel models. RESULT: The average number of depressive symptoms varies across Census tracts independent of individual-level characteristics. Symptoms are not significantly associated with neighborhood SES, ethnic composition, or age structure when individual-level characteristics are controlled statistically. However, net of individual-level characteristics, symptoms are positively associated with neighborhood residential stability, pointing to a complex meaning of residential stability for the older population. DISCUSSION: This study shows that apparent neighborhood-level socioeconomic effects on depressive symptoms among urban-dwelling older adults are largely if not entirely compositional in nature. Further, residential stability in the urban neighborhood may not be emotionally beneficial to its aged residents.

Urban neighborhood context, educational attainment, and cognitive function among older adults.

Existing research has not addressed the potential impact of neighborhood context--educational attainment of neighbors in particular--on individual-level cognition among older adults. Using hierarchical linear modeling, the authors analyzed data from the 1993 Study of Assets and Health Dynamics Among the Oldest Old (AHEAD), a large, nationally representative sample of US adults born before 1924. Data from participants residing in urban neighborhoods (n = 3,442) were linked with 1990 US Census tract data. Findings indicate that 1) average cognitive function varies significantly across US Census tracts; 2) older adults living in low-education areas fare less well cognitively than those living in high-education areas, net of individual characteristics, including their own education; 3) this association is sustained when controlling for contextual-level median household income; and 4) the effect of individual-level educational attainment differs across neighborhoods of varying educational profiles. Promoting educational attainment among the general population living in disadvantaged neighborhoods may prove cognitively beneficial to its aging residents because it may lead to meliorations in stressful life conditions and coping deficiencies.

Perceived HIV stigma in AIDS caregiving dyads.

This study examines perceived HIV stigma in AIDS caregiving dyads in the United States, assessing the measurement of and correlates of personal stigma (among care-recipients living with HIV), courtesy stigma (among caregivers), and dyadic stigma. Survey data from 135 dyads in which the caregiver is a midlife or older mother or wife, and the care-recipient is her HIV-infected adult son or husband, are analyzed with individual-level and multilevel regression models. Results indicate that: (1) perceived stigma can be reliably measured among both persons living with HIV (PLH) and caregivers; (2) personal stigma can be distinguished from courtesy stigma; (3) perceived stigma is relatively low in this sample, and is higher among PLH than caregivers, higher among caregiving wives than mothers, and similar between PLH who are husbands and sons; (4) dyadic stigma is influenced by the caregiver's HIV status, the ethnic composition of the dyad, caregiving duration, and household income; (5) stigma discrepancy within dyads is a function of health discrepancy within dyads; and (6) differences in multivariate correlates of perceived stigma at the individual-level, in comparison to the dyad-level, suggest that dyadic stigma is a unique construct. A recognition that perceived stigma bears its own unique influence on the caregiving dyad is important for understanding how best to allocate resources aimed at alleviating stigma among individuals and families impacted by HIV.

A refined protocol for coding nursing home residents' comments during satisfaction interviews.

OBJECTIVE: This study's objective was to refine a method for coding nursing home (NH) residents' comments about their perceptions of care into unmet needs specific to the manner and frequency of care delivery. METHODS: NH residents (N=69) were interviewed with both closed-ended (i.e., forced-choice) and open-ended (i.e., residents' own words) questions about their perceptions of care across eight care domains. Unmet needs included comments indicating that residents desired a change in staff- and non-staff-related care. Staff-related unmet needs were further coded into unmet emotional support (i.e., emotional support or manner of care delivery) and instrumental (i.e., instrumental support or frequency of care) needs. RESULT: Of 66 residents who commented, 66% expressed at least one unmet need across eight care domains. Among these 44 residents, 52% and 84% had unmet emotional support and instrumental support needs, respectively (kappa=68 and.92). An additional 18% expressed both unmet emotional support and instrumental support needs. DISCUSSION: The refined method offers a systematic way to code residents' comments about their care into unmet needs related to the manner and frequency of care delivery. The findings have direct implications for the identification of care areas in need of improvement from the resident's perspective and the evaluation of improvement efforts.