Search

Background Myostatin, a cytokine produced by skeletal muscle, may influence Alzheimer's disease (AD) pathogenesis, but sparse evidence exists in humans. We assessed the association between circulating levels of myostatin at Year 1 and plasma levels of β-amyloid 42/40 at Year 2, a marker of AD pathology, in a biracial cohort of older adults. Methods We studied 403 community-dwelling older adults enrolled in the Health, Aging and Body Composition Study from Memphis, Tennessee, and Pittsburgh, PA. Mean age was 73.8 ± 3 years; 54% were female; and 52% were Black. Serum myostatin levels were measured at Year 1, plasma β-amyloid 42/40 levels in Year 2 (higher ratio indicating lower amyloid load). Multivariable linear regression analyses tested the association of serum myostatin with plasma levels of β-amyloid 42/40 adjusted for computed-tomography-derived thigh muscle cross-sectional area, demographics, APOe4 allele, and risk factors for dementia. We tested for 2-way.interactions between myostatin and race or sex; results were stratified by race and sex. Results In multivariable models, myostatin was positively associated with plasma levels of β-amyloid 42/40 (standardized regression coefficient: 0.145, p =.004). Results were significant for white men and women (0.279, p =.009, and 0.221, p =.035, respectively) but not for Black men or women; interactions by race and gender were not statistically significant. Conclusions Higher serum myostatin was associated with lower amyloid burden, independently of APOe4 alleles, muscle area and other established risk factors for dementia. The role of myostatin in AD pathogenesis and the influence of race should be further investigated. [ABSTRACT FROM AUTHOR]

Background. Gait speed is a strong predictor of incident walking disability. The objective was to determine if gait variability adds to the prediction of incident mobility disability independent of gait speed. Methods. Participants included 379 older adults (mean age = 79 years; 78% Caucasian, and 40% men) in the Cardiovascular Health Study at the Pittsburgh site. All could ambulate independently and reported no difficulty walking a half mile. Gait characteristics were determined from a 4-meter computerized walkway. For each gait parameter, variability was defined as the standard deviation from the individual steps from two passes. Incident walking disability was obtained by phone interview every 6 months for 54 months and was defined as new difficulty walking a half mile or inability to walk a half mile. Results. Of the 379 participants, 222 (58.6%) developed incident mobility disability. In unadjusted Cox proportional hazards models gait speed, mean step length, mean stance time, and stance time variability were associated with incident mobility disability. After adjusting for gait speed, demographics, chronic conditions, prescription medications, health status, and physical activity level, only stance time variability remained an important indicator of disability. In the adjusted model, an increase in stance time variability of 0.01 seconds was associated with a 13% higher incidence of mobility disability (hazard ratio 1.13, 95% confidence interval, 1.01-1.27). Conclusions. Stance time variability is an independent predictor of future mobility disability. Future efforts are needed to determine whether interventions that decrease stance time variability will also delay mobility disability. [ABSTRACT FROM AUTHOR]

OBJECTIVES: To compare two methods for classifying an individual as sarcopenic for predicting decline in physical function in the Health, Aging and Body Composition Study. DESIGN: Observational cohort study with 5 years of follow-up. SETTING: Communities in Memphis, Tennessee, and Pittsburgh, Pennsylvania. PARTICIPANTS: Men and women aged 70 to 79 (N=2,976, 52% women, 41% black). MEASUREMENTS: Appendicular lean mass (aLM) was measured using dual energy x-ray absorptiometry, and participants were classified as sarcopenic first using aLM divided by height squared and then using aLM adjusted for height and body fat mass (residuals). Incidence of persistent lower extremity limitation (PLL) was measured according to self-report, and change in objective lower extremity performance (LEP) measures were observed using the Short Physical Performance Battery. RESULTS: There was a greater risk of incident PLL in women who were sarcopenic using the residuals sarcopenia method than in women who were not sarcopenic (hazard ratio (HR)=1.34, 95% confidence interval (CI)=1.11–1.61) but not in men. Those defined as sarcopenic using the aLM/ht2 method had lower incident PLL than nonsarcopenic men (HR=0.76, 95% CI=0.60–0.96) and women (HR=0.75, 95% CI=0.60–0.93), but these were no longer significant with adjustment for body fat mass. Using the residuals method, there were significantly poorer LEP scores in sarcopenic men and women at baseline and Year 6 and greater 5-year decline, whereas sarcopenic men defined using the aLM/ht2 method had lower 5-year decline. Additional adjustment for fat mass attenuated this protective effect. CONCLUSION: These findings suggest that sarcopenia defined using the residuals method, a method that considers height and fat mass together, is better for predicting disability in an individual than the aLM/ht2 method, because it considers fat as part of the definition. [ABSTRACT FROM AUTHOR]

Background: While limited literacy is common and its prevalence increases with age, no prospective study has assessed whether limited literacy is associated with mortality in older adults.Objective: To assess the association of limited literacy with mortality.Design and Setting: Five-year prospective study from 1999 to 2004 of community-dwelling elders from Memphis, TN, and Pittsburgh, PA, who were from the Health, Aging, and Body Composition study. Subjects' literacy was assessed with the Rapid Estimate of Adult Literacy in Medicine. Scores were categorized into limited (0 to 8th grade reading level) or adequate literacy (> or = 9th grade reading level).Participants: Two thousand five hundred and twelve black and white elders without baseline functional difficulties or dementia.Measurements: Time to death.Results: Participants' mean age was 75.6 years, 48% were male, 38% were black, and 24% had limited literacy; the median follow-up time was 4.2 years. Compared with those with adequate literacy, those with limited literacy had a higher risk of death (19.7% vs 10.6%) with a hazard ratio (HR) of 2.03 (95% confidence intervals [CI], 1.62 to 2.55). After adjusting for demographics and socioeconomic status, co-morbid conditions, self-rated health status, health-related behaviors, health care access measures, and psychosocial status, limited literacy remained independently associated with mortality (HR 1.75; 95% CI, 1.27 to 2.41).Conclusions: Limited literacy is independently associated with a nearly 2-fold increase in mortality in the elderly. Given the growth of the aging population and the prevalence of chronic diseases, the mechanisms by which limited literacy is associated with mortality in the elderly warrant further investigation. [ABSTRACT FROM AUTHOR]

To evaluate the association between coronary atherosclerosis and subclinical brain magnetic resonance imaging (MRI) abnormalities and between coronary atherosclerosis and abnormal cognitive function (dementia/mild cognitive impairment).Cross-sectional.The Cardiovascular Health Study (CHS), an epidemiological study of risk factors for cardiovascular disease in older adults.Four hundred nine men and women, mean age 79, recruited from the Pittsburgh center of the CHS.Coronary atherosclerosis was defined according to the level of coronary artery calcification (CAC), as measured using electronic beam tomography. Subclinical brain MRI abnormalities included ventricular enlargement, white matter hyperintensities, and number of subcortical brain infarcts. Brain MRI and CAC measurements were performed between 1998 and 2000 at the Pittsburgh center of the CHS. Prevalence of brain MRI abnormalities and abnormal cognitive status were examined across quartiles of the CAC score, before and after controlling for age. Multivariate logistic regression models were used to assess whether CAC level was associated with abnormalities of brain MRI or abnormal cognitive status.Older adults with high CAC scores were more likely to have more-severe brain MRI abnormalities, including subcortical infarction and high white matter hyperintensities. The associations between CAC and ventricular enlargement showed a similar but not significant trend. The presence of any of the MRI abnormalities attenuated the association between CAC and abnormal cognitive status.Older adults with higher levels of CAC were more likely to have more-severe brain MRI abnormalities and abnormal cognitive status. [ABSTRACT FROM AUTHOR]

OBJECTIVES: To describe gait variability at usual and fast walking speeds in community-dwelling older adults and to describe the effects of increasing gait speed on gait variability. DESIGN: Cross-sectional, descriptive study. SETTING: The Cardiovascular Health Study at the University of Pittsburgh. PARTICIPANTS: Ninety-five community-living older adults, 54 women and 41 men, age 65 and older (mean age ± standard deviation 79.4 ± 3.37). MEASUREMENTS: Gait measured at participant's usual and fast walking speed collected using an instrumented walkway. Step-length and step-width variability were determined using the coefficient of variation. CONCLUSIONS: Step-length and step-width variability have opposite associations with gait speed in older adults. Improvement in step-length and step-width variability with attempted acceleration might be a key factor to examine in future studies of disability risk and therapeutic interventions. [ABSTRACT FROM AUTHOR]