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Biomedical subjects

Michael Nevitt

Publications and source records attributed to Michael Nevitt.

17 recordsLinked to original sources
PubMed2006

Lower prevalence of chondrocalcinosis in Chinese subjects in Beijing than in white subjects in the United States: the Beijing Osteoarthritis Study.

OBJECTIVE: Chondrocalcinosis, which can promote joint inflammation and cartilage degeneration, is highly prevalent in elderly white subjects. Data on its prevalence are scarce in other ethnic populations. This study was undertaken to compare the prevalence of chondrocalcinosis in Chinese subjects with that in white subjects. METHODS: We recruited a random sample of Beijing residents ages >or=60 years. Participants underwent standard weight-bearing anteroposterior knee radiography and posteroanterior hand radiography using the protocols developed in the Framingham Osteoarthritis Study. Radiographic chondrocalcinosis was defined as present in a knee or wrist when there was evidence of definite linear cartilage calcification. We compared the prevalence of chondrocalcinosis in Chinese subjects with that in white subjects using age-standardized prevalence ratios. We used identical methods to collect samples of tap water from 2 cities and measured their levels of calcium, magnesium, and phosphate in the same laboratory. RESULTS: Chinese subjects had a much lower prevalence of knee chondrocalcinosis (1.8% in men, 2.7% in women) than did white subjects (6.2% in men, 7.7% in women), with the age-standardized prevalence ratio being 0.34 (95% confidence interval [95% CI] 0.20-0.54) and 0.43 (95% CI 0.31-0.59) in men and women, respectively. Wrist chondrocalcinosis was rare in elderly Chinese subjects (prevalence 0.3% in men and 1.0% in women), with the age-standardized prevalence ratio being 0.06 (95% CI 0.01-0.18) in Chinese men and 0.18 (95% CI 0.10-0.30) in Chinese women. Calcium levels in the tap water in Beijing were 15-fold higher than in Framingham, whereas no difference was found in magnesium and phosphate levels. CONCLUSION: Knee chondrocalcinosis and wrist chondrocalcinosis are far less common in Chinese subjects in Beijing than in US white subjects in Framingham, Massachusetts. Given the current lack of understanding of the etiology of chondrocalcinosis, further epidemiologic studies of the impact of genetic and environmental factors on occurrence of chondrocalcinosis are indicated.

Age Distribution↗
PubMed2006

The loss of skeletal muscle strength, mass, and quality in older adults: the health, aging and body composition study.

BACKGROUND: The loss of muscle mass is considered to be a major determinant of strength loss in aging. However, large-scale longitudinal studies examining the association between the loss of mass and strength in older adults are lacking. METHODS: Three-year changes in muscle mass and strength were determined in 1880 older adults in the Health, Aging and Body Composition Study. Knee extensor strength was measured by isokinetic dynamometry. Whole body and appendicular lean and fat mass were assessed by dual-energy x-ray absorptiometry and computed tomography. RESULTS: Both men and women lost strength, with men losing almost twice as much strength as women. Blacks lost about 28% more strength than did whites. Annualized rates of leg strength decline (3.4% in white men, 4.1% in black men, 2.6% in white women, and 3.0% in black women) were about three times greater than the rates of loss of leg lean mass ( approximately 1% per year). The loss of lean mass, as well as higher baseline strength, lower baseline leg lean mass, and older age, was independently associated with strength decline in both men and women. However, gain of lean mass was not accompanied by strength maintenance or gain (ss coefficients; men, -0.48 +/- 4.61, p =.92, women, -1.68 +/- 3.57, p =.64). CONCLUSIONS: Although the loss of muscle mass is associated with the decline in strength in older adults, this strength decline is much more rapid than the concomitant loss of muscle mass, suggesting a decline in muscle quality. Moreover, maintaining or gaining muscle mass does not prevent aging-associated declines in muscle strength.

Aged↗
PubMed2005

Obesity, regional body fat distribution, and the metabolic syndrome in older men and women.

BACKGROUND: The metabolic syndrome is a disorder that includes dyslipidemia, insulin resistance, and hypertension and is associated with an increased risk of diabetes and cardiovascular disease. We determined whether patterns of regional fat deposition are associated with metabolic syndrome in older adults. METHODS: A cross-sectional study was performed that included a random, population-based, volunteer sample of Medicare-eligible adults within the general communities of Pittsburgh, Pa, and Memphis, Tenn. The subjects consisted of 3035 men and women aged 70 to 79 years, of whom 41.7% were black. Metabolic syndrome was defined by Adult Treatment Panel III criteria, including serum triglyceride level, high-density lipoprotein cholesterol level, glucose level, blood pressure, and waist circumference. Visceral, subcutaneous abdominal, intermuscular, and subcutaneous thigh adipose tissue was measured by computed tomography. RESULTS: Visceral adipose tissue was associated with the metabolic syndrome in men who were of normal weight (odds ratio, 95% confidence interval: 2.1, 1.6-2.9), overweight (1.8, 1.5-2.1), and obese (1.2, 1.0-1.5), and in women who were of normal weight (3.3, 2.4-4.6), overweight (2.4, 2.0-3.0), and obese (1.7, 1.4-2.1), adjusting for race. Subcutaneous abdominal adipose tissue was associated with the metabolic syndrome only in normal-weight men (1.3, 1.1-1.7). Intermuscular adipose tissue was associated with the metabolic syndrome in normal-weight (2.3, 1.6-3.5) and overweight (1.2, 1.1-1.4) men. In contrast, subcutaneous thigh adipose tissue was inversely associated with the metabolic syndrome in obese men (0.9, 0.8-1.0) and women (0.9, 0.9-1.0). CONCLUSION: In addition to general obesity, the distribution of body fat is independently associated with the metabolic syndrome in older men and women, particularly among those of normal body weight.

Adipose Tissue↗
PubMed2005

Weight change and the conservation of lean mass in old age: the Health, Aging and Body Composition Study.

BACKGROUND: Weight loss may contribute to the loss of lean mass with age. OBJECTIVE: The objective was to evaluate the relation between weight loss or weight gain and changes in lean mass and fat mass in older adults. DESIGN: We observed changes in weight and body composition during a 4-y period in 2163 men (47%) and women (53%) aged 70-79 y in the Health, Aging and Body Composition Study cohort. Whole-body and appendicular bone-free lean mass and fat mass were measured by using dual-energy X-ray absorptiometry. RESULTS: Weight loss and weight gain were common. In both weight losers and weight gainers, changes in lean mass as a percentage of initial lean mass were substantially smaller than changes in fat mass as a percentage of initial fat mass. However, the difference between the change in lean mass and that in fat mass was more pronounced with weight gain than with weight loss, especially in men. Small amounts of lean loss and fat gain were noted with weight stability. In multivariate models, weight loss was strongly associated with lean mass loss in both men and women, especially in men whose weight loss was concurrent with a hospitalization. CONCLUSIONS: With weight change, a greater proportion of lean mass than of fat mass was conserved, but, especially in older men, significantly more lean mass was lost with weight loss than was gained with weight gain. These findings suggest that weight loss, even with regain, could accelerate sarcopenia in older adults.

Absorptiometry, Photon↗
PubMed2005

Muscle mass, muscle strength, and muscle fat infiltration as predictors of incident mobility limitations in well-functioning older persons.

BACKGROUND: Lower muscle mass has been correlated with poor physical function; however, no studies have examined this relationship prospectively. This study aims to investigate whether low muscle mass, low muscle strength, and greater fat infiltration into the muscle predict incident mobility limitation. METHODS: Our study cohort included 3075 well-functioning black and white men and women aged 70-79 years participating in the Health, Aging, and Body Composition study. Participants were followed for 2.5 years. Muscle cross-sectional area and muscle tissue attenuation (a measure of fat infiltration) were measured by computed tomography at the mid-thigh, and knee extensor strength by using a KinCom dynamometer. Incident mobility limitation was defined as two consecutive self-reports of any difficulty walking one-quarter mile or climbing 10 steps. RESULTS: Mobility limitations were developed by 22.3% of the men and by 31.8% of the women. Cox's proportional hazards models, adjusting for demographic, lifestyle, and health factors, showed a hazard ratio of 1.90 [95% confidence interval (CI), 1.27-2.84] in men and 1.68 (95% CI, 1.23-2.31) in women for the lowest compared to the highest quartile of muscle area (p <.01 for trend). Results for muscle strength were 2.02 (95% CI, 1.39-2.94) and 1.91 (95% CI, 1.41-2.58), p <.001 trend, and for muscle attenuation were 1.91 (95% CI, 1.31-2.83) and 1.68 (95% CI, 1.20-2.35), p <.01 for trend. When included in one model, only muscle attenuation and muscle strength independently predicted mobility limitation (p < .05). Among men and women, associations were similar for blacks and whites. CONCLUSION: Lower muscle mass (smaller cross-sectional thigh muscle area), greater fat infiltration into the muscle, and lower knee extensor muscle strength are associated with increased risk of mobility loss in older men and women. The association between low muscle mass and functional decline seems to be a function of underlying muscle strength.

Aged↗
PubMed2004

Quadriceps weakness and its relationship to tibiofemoral and patellofemoral knee osteoarthritis in Chinese: the Beijing osteoarthritis study.

OBJECTIVE: Weakness has been documented as a feature of tibiofemoral knee osteoarthritis (OA) and may cause disease in this compartment by shock absorption during impulse loading at heel strike, when the patellofemoral joint is not engaged. Our objective was to determine the association of muscle weakness with compartment-specific knee OA, to evaluate sex-specific differences in this relationship, and to determine, by evaluating asymptomatic individuals with OA, whether symptoms may produce the weakness seen in OA. METHODS: This cross-sectional study involved 2,472 subjects (1,475 women and 997 men) ages 60 years or older from 4 central districts of Beijing, China. For all subjects, a skyline view of each knee and an anteroposterior (AP) or posteroanterior (PA) radiograph of both knees were obtained during weight bearing. Radiographs were read by one reader for Kellgren/Lawrence (K/L) grade, joint space narrowing (JSN), and osteophytes. We defined a subject as having tibiofemoral OA when the K/L grade was > or =2 on AP/PA view, patellofemoral OA on skyline view when the osteophyte score was > or =2 (or when the JSN score was > or =2 and the osteophyte score was > or =1), and mixed OA when the knee had both patellofemoral and tibiofemoral radiographic OA. Strength was measured isometrically for each leg separately, and knee pain was evaluated by questionnaire. RESULTS: In women, quadriceps weakness was associated with tibiofemoral OA (odds ratio [OR] 0.7, 95% confidence interval [95% CI] 0.4-1.0), patellofemoral OA (OR 0.6, 95% CI 0.4-0.9), and mixed OA (OR 0.4, 95% CI 0.3-0.6). In men, weakness was associated with mixed OA (OR 0.5, 95% CI 0.3-0.8), and the ORs suggesting an association of patellofemoral OA with weakness were the same as those in women, although in men this trend did not reach statistical significance (P = 0.12). In men, isolated tibiofemoral disease was not associated with weakness; however, the sample size in this analysis was limited. When subjects with knee symptoms were excluded, the relationship of quadriceps weakness to OA was attenuated, with only the relationship between muscle weakness and mixed OA remaining significant. CONCLUSION: There is a relationship between quadriceps weakness and knee OA in all compartments, with the strongest association in mixed disease. Pain may contribute to some of this weakness.

Aged↗
PubMed2004

The association of regional fat depots with hypertension in older persons of white and African American ethnicity.

BACKGROUND: Fat distribution has been shown to be a strong correlate of hypertension, independent of general obesity. However, population-based studies are lacking on the association of regional fat depots with hypertension. METHODS: The present study is a cross-sectional analysis of 2969 individuals in the Health, Aging and Body Composition Study (915 men of white ethnicity and 535 of African American; and 833 women of white ethnicity and 686 of African American) who were 70 to 79 years of age. Fat depots were measured by computed tomography. RESULTS: The prevalence of hypertension was 57%. Among those with hypertension, 70% reported antihypertensive treatment. In logistic regression analyses, visceral fat was strongly associated with hypertension (odds ratios for each standard deviation increase in the area of visceral fat: 1.28, P < .0001) after adjustment for age, sex, ethnicity, site, height, smoking status, pack-years of smoking, alcohol consumption status, amount of alcohol consumption, and physical activity. Moreover, the association was the strongest in individuals with the least amount of total body fat. Besides visceral fat, subcutaneous fat and thigh intermuscular fat were also associated with hypertension in African Americans. CONCLUSIONS: Larger amounts of visceral fat may indicate a high risk of hypertension in older adults, especially in lean individuals.

Adipose Tissue↗
PubMed2004

Higher risk of multiple falls among elderly women who lose visual acuity.

OBJECTIVE: To determine the association between changes in visual acuity (VA) and frequent falls in older women. DESIGN: Prospective cohort study. PARTICIPANTS: Two thousand two elderly community-residing women participating in the Study of Osteoporotic Fractures with measurements of VA at baseline and a follow-up examination 4 to 6 years later (mean of 5.6 years). METHODS: Binocular VA with habitual correction was measured under standard illumination using Bailey-Lovie charts at baseline and fourth examinations. Change in VA was stratified into 5 categories: no change or VA gain, loss of 1 to 5 letters, loss of 6 to 10 letters, loss of 11 to 15 letters, and loss of >15 letters. A separate analysis considered decline in VA as the loss of >or=10 letters (>or=2 lines) on the Bailey-Lovie acuity measure between baseline and follow-up examinations. MAIN OUTCOME MEASURES: Data on falls were obtained from postcards sent every 4 months after the follow-up examination. Frequent falling was defined as >or=2 falls during a 1-year period after the follow-up examination. RESULTS: Compared with women with stable or improved VA, women with declining acuity had significantly greater odds of experiencing frequent falling during the subsequent year. Odds ratios after adjustment for baseline acuity and other confounders were 2.08 (95% confidence interval [CI]: 1.39-3.12) for loss of 1 to 5 letters, 1.85 (95% CI: 1.16-2.95) for loss of 6 to 10 letters, 2.51 (95% CI: 1.39-4.52) for loss of 11 to 15 letters, and 2.08 (95% CI: 1.01-4.30) for loss of >15 letters. In the analysis of visual decline defined as a loss of >or=10 letters, heightened risk of frequent falling was evident in each of 2 subgroups defined by splitting the sample on baseline VA, with borderline significant evidence of a more pronounced effect in those women with baseline VA of 20/40 or worse (P value for interaction, 0.083). CONCLUSIONS: Loss of vision among elderly women increases the risk of frequent falls. Prevention or correction of visual loss may help reduce the number of future falls.

Accidental Falls↗
PubMed2004

Inflammatory markers and incident mobility limitation in the elderly.

OBJECTIVES: To examine the relationship between indicators of inflammation and the incidence of mobility limitation in older persons. DESIGN: Prospective cohort study: the Health, Aging and Body Composition Study. SETTING: Pittsburgh, Pennsylvania, and Memphis, Tennessee. PARTICIPANTS: A total of 2,979 men and women, aged 70 to 79, without mobility limitation at baseline. MEASUREMENTS: Serum levels of interleukin (IL)-6, tumor necrosis factor alpha (TNFalpha), and C-reactive protein (CRP) and soluble cytokine receptors (IL-2sR, IL-6sR, TNFsR1, TNFsR2) were measured. Mobility limitation was assessed and defined as reporting difficulty or inability to walk one-quarter of a mile or to climb 10 steps during two consecutive semiannual assessments over 30 months. RESULTS: Of the 2,979 participants, 30.1% developed incident mobility limitation. After adjustment for confounders (demographics, prevalent conditions at baseline, body composition), the relative risk (RR) of incident mobility limitation per standard deviation (SD) increase was 1.19 (95% confidence interval (CI)=1.10-1.28) for IL-6, 1.20 (95% CI=1.12-1.29) for TNFalpha, and 1.40 (95% CI=1.18-1.68) for CRP. The association between inflammation and incident mobility limitation was especially strong for the onset of more severe mobility limitation and when the levels of multiple inflammatory markers were high. When persons with baseline or incident cardiovascular disease events or persons who were hospitalized during study follow-up were excluded, findings remained similar. In a subset (n=499), high levels of the soluble receptors IL2sR and TNFsR1 (per SD increase: RR=1.23 (95% CI=1.04-1.46) and RR=1.28 (95% CI=1.04-1.57), respectively) were also associated with incident mobility limitation. CONCLUSION: Findings suggest that inflammation is prognostic for incident mobility limitation over 30 months, independent of cardiovascular disease events and incident severe illness.

Aged↗
PubMed2003

A randomized controlled trial of a Chinese herbal remedy to increase energy, memory, sexual function, and quality of life in elderly adults in Beijing, China.

BACKGROUND: Chinese herbal medicines are commonly used to improve general health and well-being despite limited scientific data to support their efficacy. We conducted a randomized, double-blind, placebo-controlled trial to determine whether an herbal remedy that is used widely in China was associated with changes in quality of life, energy, memory, sexual function, and qi (the Chinese concept of "vital energy" that is important in general health). METHODS: Residents (n = 237) of Beijing, China, who were aged > or =60 years and had self-reported decreased energy, memory, or sexual function, were randomly assigned to take four tablets of a Chinese herbal formula or of an identical placebo, three times a day for 30 days. Patients returned for one follow-up visit after 30 days for assessment of all outcomes. The main outcome measures were changes in quality of life at 30 days as measured by the 12-Item Short Form Health Survey (SF-12) Mental and Physical Component Summary scales. RESULTS: Use of Chinese herbs was associated with a small benefit in the Mental Component scale (difference of 1.9 points; 95% confidence interval [CI]: 0.1 to 3.6) and no benefit in the Physical Component scale (difference of -0.1 points; 95% CI: -1.7 to 1.5) as compared with placebo. A small improvement in the qi scale was no longer significant after adjusting for baseline differences in this score between groups. There was no improvement in physical performance, memory, or sexual function. The herbal product was well tolerated. CONCLUSION: Short-term use of a mixture of Chinese herbs was associated with a small benefit in one measure of mental health that is of unclear clinical importance.

Aged↗
PubMed2003

Strength and muscle quality in a well-functioning cohort of older adults: the Health, Aging and Body Composition Study.

OBJECTIVES: To determine whether lower lean mass and higher fat mass have independent effects on the loss of strength and muscle quality in older adults and might explain part of the effect of age. DESIGN: Single-episode, cross-sectional analyses of a cohort of subjects in the Health, Aging and Body Composition (Health ABC) Study. SETTING: Ambulatory clinic and research laboratory. PARTICIPANTS: Two thousand six hundred twenty-three men and women aged 70 to 79 from the Health ABC Study. MEASUREMENTS: Upper and lower extremity strength was measured using isokinetic (knee extension) and isometric (grip strength) dynamometers. Body composition (lean mass and fat mass) was determined by measuring lean mass of upper and lower extremities and the total body by dual-energy x-ray absorptiometry. Muscle quality was ascertained by taking the ratio of strength to muscle mass for both upper and lower extremities. RESULTS: Upper and lower extremity strength and muscle quality decreased as age increased. Most of the explained variance in strength was due to differences in muscle mass, but, in those at the extremes of body fat and lower leg muscle quality, the association with body fat was independent of the effect of age. Although blacks had greater muscle strength and mass than whites, leg muscle quality tended to be lower in blacks than in whites. Upper extremity strength adjusted for lean mass and muscle quality were also associated inversely and independently with age, body fat, and black race. CONCLUSION: In this older cohort, lower strength with older age was predominantly due to a lower muscle mass. Age and body fat also had significant inverse associations with strength and muscle quality. Both preservation of lean mass and prevention of gain in fat may be important in maintaining strength and muscle quality in old age.

Age Factors↗
PubMed2003

Sarcopenia: alternative definitions and associations with lower extremity function.

OBJECTIVES: To compare two sarcopenia definitions and examine the relationship between them and lower extremity function and other health related factors using data from the baseline examination of the Health Aging and Body Composition (Health ABC) Study. DESIGN: Observational cohort study. SETTING: Two U.S. communities in Memphis, Tennessee, and Pittsburgh, Pennsylvania. PARTICIPANTS: Participants were aged 70 to 79 (N=2984, 52% women, 41% black). MEASUREMENTS: Participants were assessed using dual energy x-ray absorptiometry and were classified as sarcopenic using two different approaches to adjust lean mass for body size: appendicular lean mass divided by height-squared (aLM/ht2) and appendicular lean mass adjusted for height and body fat mass (residuals). RESULTS: These methods differed substantially in the classification of individuals as being sarcopenic, especially those who were more obese. The former method was highly correlated with body mass index and identified fewer overweight or obese individuals as sarcopenic. In both men and women, none of the obese group would be considered sarcopenic using the aLM/ht2 method, compared with 11.5% of men and 21.0% of women using the residuals method. In men, both classifications of sarcopenia were associated with smoking, poorer health, lower activity, and impaired lower extremity function. Fewer associations with health factors were noted in women, but the classification based on both height and fat mass was more strongly associated with lower extremity functional limitations (odds ratio (OR)=0.9, 95% confidence interval (CI)=0.7-1.2 for low kg/ht2; OR=1.9, 95% CI=1.4-2.5 for lean mass adjusted for height and fat mass). CONCLUSION: These findings suggest that fat mass should be considered in estimating prevalence of sarcopenia in women and in overweight or obese individuals.

Absorptiometry, Photon↗
PubMed2003

Comparison of the effectiveness of 2 dual-energy X-ray absorptiometers with that of total body water and computed tomography in assessing changes in body composition during weight change.

BACKGROUND: Little information is available on the assessment of changes in body composition as a function of weight change with the use of the fan beam of dual-energy X-ray absorptiometry (DXA). OBJECTIVE: The objective was to determine the accuracy of the fan beam of the QDR 4500A densitometer and the pencil beam of the QDR 2000 densitometer in estimating changes in whole-body lean soft tissue mass (LSTM(DXA)) and fat mass (FM) with weight change. DESIGN: Thirty-seven subjects who lost 5.7 +/- 4.5 kg were measured before and after weight change. Using total body water and computed tomography (CT) of the midthigh, we compared changes in FFM(TBW) and LSTM(CT) with changes in LSTM(DXA). RESULTS: Overall, compared with TBW, the fan beam gave a larger estimate of change (macro x +/- SD) in LSTM (fan beam - TBW: -0.7 +/- 1.6 kg) than did the pencil beam (pencil beam - TBW: -0.1 +/- 1.6 kg). When the change in LSTM obtained with the fan beam and pencil beam was regressed against the change in FFM(TBW), the slope of the line for the fan beam was 0.97 (r(2) = 0.61) and that for the pencil beam was 0.86 (r(2) = 0.61). Regression analysis showed that the results between the 2 units were not interchangeable. For the midthigh region, the change in LSTM(CT) was moderately correlated with the change in LSTM(DXA) with the fan beam and pencil beam. CONCLUSIONS: The measurement of change in LSTM with the fan and pencil beams provides the same relation to changes in FFM assessed by TBW, but the 2 systems are not interchangeable.

Absorptiometry, Photon↗
PubMed2003

How does low back pain impact physical function in independent, well-functioning older adults? Evidence from the Health ABC Cohort and implications for the future.

OBJECTIVE: To determine the relationships between low back pain (LBP) frequency and intensity and self-reported and performance-based physical function in a large cohort of well-functioning older adults. DESIGN: Cross-sectional survey and examination. SETTING: Community-based cohort of the Health, Aging, and Body Composition (Health ABC) study. PARTICIPANTS: Participants were 2,766 community-dwelling adults, aged 70-79; 42% were African American, 52% were men. OUTCOME MEASURES: 1) Back pain-location, frequency, intensity; 2) Hip and/or knee pain; 3) Body mass index (BMI); 4) Self-reported difficulty doing functional tasks; 5) Lower extremity function, using the battery from the Established Populations for Epidemiologic Studies in the Elderly (EPESE); 6) Self-rated health; 7) Comorbidity; 8) Depressive symptoms, using the Center for Epidemiological Studies-Depression (CES-D) scale. RESULTS: LBP was common (36%), and its frequency/intensity was significantly associated with other pain and comorbidities. In gender-specific models, LBP frequency/intensity was not significantly associated with EPESE performance score after adjusting for age, race, BMI, CES-D score, knee pain, hip pain, and other comorbidities. LBP frequency/intensity, however, was significantly associated with self-reported difficulty with most functional tasks after adjusting for important confounders. CONCLUSIONS: Among well-functioning community-dwelling older adults, LBP frequency/intensity was associated with perceived difficulty in performing important functional tasks, but not with observed physical performance. The demonstrated dose-response relationship between pain frequency/intensity and self-reported task performance difficulty underscores the importance of clinical efforts to treat pain without necessarily eradicating it. Additional work is needed to determine whether back pain is associated with a risk for progressive functional decline and loss of independence in older adults and whether therapeutic interventions can ameliorate decline and, therefore, preserve independence.

Activities of Daily Living↗
PubMed2002

Leg muscle mass and composition in relation to lower extremity performance in men and women aged 70 to 79: the health, aging and body composition study.

OBJECTIVES: The loss of muscle mass with aging, or sarcopenia, is hypothesized to be associated with the deterioration of physical function. Our aim was to determine whether low leg muscle mass and greater fat infiltration in the muscle were associated with poor lower extremity performance (LEP). DESIGN: A cross-sectional study, using baseline data of the Health, Aging and Body Composition study (1997/98). SETTING: Medicare beneficiaries residing in ZIP codes from the metropolitan areas surrounding Pittsburgh, Pennsylvania, and Memphis, Tennessee. PARTICIPANTS: Three thousand seventy-five well-functioning black and white men and women aged 70 to 79. MEASUREMENTS: Two timed tests (6-meter walk and repeated chair stands) were used to measure LEP. Muscle cross-sectional area and muscle tissue attenuation (indicative of fat infiltration) were obtained from computed tomography scans at the midthigh. Body fat was assessed using dual-energy x-ray absorptiometry. RESULTS: Blacks had greater muscle mass and poorer LEP than whites. Black women had greater fat infiltration into the muscle than white women. After adjustment for clinic site, age, height, and total body fat, smaller muscle area was associated with poorer LEP in all four race-gender groups. (Regression coefficients, expressed per standard deviation (+/-55 cm2) of muscle area, were 0.658 and 0.519 in white and black men and 0.547 and 0.435 in white and black women, respectively, P <.01.) In addition, reduced muscle attenuation-indicative of greater fat infiltration into the muscle-was associated with poorer LEP, independent of total body fat and muscle area. (Regression coefficients per standard deviation (= 7 Hounsfield Units) of muscle attenuation were 0.292 and 0.224 in white and black men, and 0.193 and 0.159 in white and black women, respectively, P <.05). The most important body composition components related to LEP were muscle area in men and total body fat in women. Results were similar after additional adjustment for lifestyle factors and health status. No interactions between race and muscle area (P>.7) or between race and muscle attenuation (P>.2) were observed. CONCLUSION: Smaller midthigh muscle area and greater fat infiltration in the muscle are associated with poorer LEP in well-functioning older men and women.

Absorptiometry, Photon↗
PubMed2002

Relationship of interleukin-6 and tumor necrosis factor-alpha with muscle mass and muscle strength in elderly men and women: the Health ABC Study.

BACKGROUND: A decline in muscle mass and muscle strength characterizes normal aging. As clinical and animal studies show a relationship between higher cytokine levels and low muscle mass, the aim of this study was to investigate whether markers of inflammation are associated with muscle mass and strength in well-functioning elderly persons. METHODS: We used baseline data (1997-1998) of the Health, Aging, and Body Composition (Health ABC) Study on 3075 black and white men and women aged 70-79 years. Midthigh muscle cross-sectional area (computed tomography), appendicular muscle mass (dual-energy x-ray absorptiometry), isokinetic knee extensor strength (KinCom), and isometric grip strength were measured. Plasma levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) were assessed by enzyme-linked immunosorbent assay (ELISA). RESULTS: Higher cytokine levels were generally associated with lower muscle mass and lower muscle strength. The most consistent relationship across the gender and race groups was observed for IL-6 and grip strength: per SD increase in IL-6, grip strength was 1.1 to 2.4 kg lower (p <.05) after adjustment for age, clinic site, health status, medications, physical activity, smoking, height, and body fat. An overall measure of elevated cytokine level was created by combining the levels of IL-6 and TNF-alpha. With the exception of white men, elderly persons having high levels of IL-6 (>1.80 pg/ml) as well as high levels of TNF-alpha (>3.20 pg/ml) had a smaller muscle area, less appendicular muscle mass, a lower knee extensor strength, and a lower grip strength compared to those with low levels of both cytokines. CONCLUSIONS: Higher plasma concentrations of IL-6 and TNF-alpha are associated with lower muscle mass and lower muscle strength in well-functioning older men and women. Higher cytokine levels, as often observed in healthy older persons, may contribute to the loss of muscle mass and strength that accompanies aging.

Aged↗