Dana Miller-Martinez

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 7s, 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.

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.

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.

The role of family caregivers in HIV medication adherence

Abstract This study examines the role that mid-life and older wives and mothers play in promoting medication adherence among their HIV-infected husbands or adult sons who require daily living assistance. Interviews were conducted with 112 caregiving dyads, with caregivers reporting on their own behaviours and attitudes towards medications, and care-recipients (persons living with HIV [PLH]) providing information about their own adherence practices. By examining how caregiver characteristics, behaviours, and attitudes may influence PLH adherence it is explicitly recognized that caregivers and PLH are linked within a caregiving dyad. Findings indicate that caregivers often remind PLH to take medications, but these reminders are not significantly associated with adherence. Caregivers also report strong attitudes about medication hassles, concerns over treatment failure and general concerns about adherence. Controlling for background characteristics, high perceived adherence hassles on the part of the caregiver were associated with low PLH adherence, providing evidence of shared influence within the caregiving dyad. Adherence interventions may maximize their effectiveness if they consider the role of the family caregiver because these data suggest that caregiver attitudes are linked with PLH adherence behaviours.

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.

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.

HIV-related traumatic stress symptoms in AIDS caregiving family dyads.

Abstract This study assesses HIV-related traumatic stress symptoms in 135 AIDS caregiving family 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. Symptoms of HIV-related traumatic stress can be reliably measured in these dyads, with both caregivers and care-recipients reporting avoidant and intrusive thoughts. Among care-recipients, high symptoms are associated with high daily living assistance requirements, low dyadic adjustment, and high constriction of social activities. Among caregivers, high symptoms of traumatic stress are associated with being HIV positive, feeling overloaded by caregiving demands, and perceiving high levels of HIV stigma. Caregiving mothers and wives may feel traumatized ‘courtesy’ of their loved ones HIV infection, the caregiving scenario, or the resultant caregiving stress.

Family Caregiver Involvement and Satisfaction With Institutional Care During the 1st Year After Admission

The purpose of this research is to examine the relationship between caregivers’ involvement and their satisfaction with institutional care during the 1st year. This panel study includes 145 care-givers. A summary indicator of satisfaction was analyzed (a) near admission and (b) for change 1 year after admission. Caregivers were least satisfied with physicians and the number of staff at both time points. Satisfaction at admission and change in satisfaction from admission to 1 year later were regressed on caregivers’ involvement after controlling for caregivers’ depression, family tension, and perceived behavioral problems of their relatives. Multivariate results indicated that more involved caregivers at admission were less satisfied with institutional care at admission and became less satisfied during the year after admission. More involved caregivers may be less satisfied because they see firsthand problems with nursing home care and because a meaningful caregiving role after institutionalization is not facilitated by nursing homes.

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

ABSTRACT 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.