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Biomedical subjects

T B Harris

Publications and source records attributed to T B Harris.

At least 37 records · Page 2Linked to original sources
PubMed2000

Cross-sectional and prospective relationships of interleukin-6 and C-reactive protein with physical performance in elderly persons: MacArthur studies of successful aging.

BACKGROUND: Chronic inflammation has been proposed as a biological mechanism underlying the decline in physical function that occurs with aging. The purpose of this investigation was to examine the cross-sectional and prospective relationships between markers of inflammation, interleukin-6 (IL-6) and C-reactive protein (CRP), with several measures of physical performance in older persons aged 70 to 79 years. METHODS: Subjects were 880 high-functioning men and women participating in the MacArthur Study of Successful Aging (n = 1189), a subset of the Established Populations for Epidemiologic Studies of the Elderly (n = 4030). Plasma IL-6 and CRP levels were determined by enzyme-linked immunosorbent assay and log transformed to normalize the distributions. Physical function measures included handgrip strength, signature time, chair stands (time to complete five repetitions), and 6-m walk time. RESULTS: Women had lower (p < .05) IL-6 levels than men, but there was no significant difference between blacks and whites. IL-6 and CRP levels were higher (p < .05) in current smokers than in nonsmokers and in those with a greater body mass index (BMI). Hours per year undertaking moderate and strenuous physical activity were also related to inflammatory markers with higher (p < .001) IL-6 and CRP levels in less active individuals. After adjusting for age, sex, race, BMI, smoking status, use of nonsteroidal anti-inflammatory drugs, and prevalence of morbidity, those in the top two quartiles for walking speed had lower (p = .012) IL-6 levels than those in the bottom quartile. In addition, there was a trend (p = .038) for lower CRP levels in those with higher walking speed. CRP levels were also lower (p = .04) in individuals in the top quartile for grip strength. No significant differences were noted for chair stands or signature time performance. Repeat performance measures obtained on 405 subjects (67% of those eligible at baseline) obtained 7 years later had declined significantly (grip strength, 18%; signature time, 21%; walking speed, 31%; p < .001), except for the chair rise; however, baseline IL-6 and CRP were not associated with a change in performance. However, those who died or who were unable to undergo testing had higher baseline IL-6 and CRP levels (p < .01) and slower walking speed (p < .05). CONCLUSIONS: Although IL-6 has been shown to predict onset of disability in older persons and both IL-6 and CRP are associated with mortality risk, these markers of inflammation have only limited associations with physical performance, except for walking measures and grip strength at baseline, and do not predict change in performance 7 years later in a high-functioning subset of older adults.

Aged↗
PubMed2000

Change in muscle mass and muscle strength after a hip fracture: relationship to mobility recovery.

BACKGROUND: Hip fracture in elderly persons has a serious impact on long-term physical function. This study determines the change in muscle strength and muscle mass after a hip fracture, and the associations between these changes and mobility recovery. METHODS: Ninety community-dwelling women aged 65 years and older who had recently experienced a fracture of the proximal femur were included in the study. At 2 to 10 days after hospital admission, the women's grip strength, ankle dorsiflexion strength, and regional muscle mass (by dual-energy x-ray absorptiometry) were measured, and the prefracture level of independence for five mobility function items was assessed. All measurements were repeated at 12 months. RESULTS: At follow-up, only 17.8% of the women had returned to their prefracture level of mobility function for all five items. Mobility function recovery was not related to change in skeletal muscle mass of the nonfractured leg or the arms. However, women who lost grip strength (mean loss of -28.7%, SD = 16.9%), or who lost ankle strength of the nonfractured leg (mean loss of -21.5%, SD = 14.7%), had a worse mobility recovery compared with those who gained strength (p = .04 and p = .09, respectively). In addition, chronic disease (p = .03), days hospitalized (p = .04), and self-reported hip pain (p = .07) were independent predictors of decline in mobility function. CONCLUSIONS: The results suggest that loss of muscle strength, but not loss of muscle mass, is an independent predictor of poorer mobility recovery 12 months after a hip fracture. When confirmed by other studies, these findings may have implications for rehabilitation strategies after a hip fracture.

Aged↗
PubMed2000

The prognostic value of serum albumin in healthy older persons with low and high serum interleukin-6 (IL-6) levels.

OBJECTIVE: We sought to determine the prognostic value of serum albumin for 4-year mortality among high-functioning persons who did or did not have evidence of inflammation as indicated by high interleukin-6 (IL-6) levels. DESIGN: We used a case-cohort design of healthy, nondisabled older persons who had serum albumin and plasma IL-6 measured at baseline. Crude and multiply adjusted (for sociodemographics and chronic diseases) proportional hazards models were used to identify the effect of baseline levels of serum albumin level on 4-year mortality among those with higher and lower levels of IL-6. RESULTS: Among subjects without evidence of IL-6-mediated inflammation (IL-6 < 3.20 pg/mL), having a lower (< or = 4.4 g/dL) albumin level was associated with a multiply adjusted relative risk of 2.1 for 4-year mortality compared with those with higher albumin. In the presence of inflammation (IL-6 > or = 3.20 pg/mL), higher and lower serum albumin levels had similar risks (adjusted relative risks 4.0 and 3.8, respectively) compared with the referent group (higher albumin and low IL-6). CONCLUSIONS: High serum albumin has a protective effect in healthy older persons who do not have evidence of cytokine-mediated inflammation. This protective effect is not conferred in presence of inflammation. The mechanisms by which inflammation eliminates the protective effect of high albumin remain to be determined.

Aged↗
PubMed2000

Subsystems contributing to the decline in ability to walk: bridging the gap between epidemiology and geriatric practice in the InCHIANTI study.

BACKGROUND: Older patients are often referred to geriatricians because of complaints of progressive difficulties in walking. The diagnostic and therapeutic approach to these patients is complex. Multiple physiologic subsystems may influence the ability to walk, and no standard criteria are currently available to establish whether these subsystems are functioning within the normal range. To address this lack of knowledge we conducted the InCHIANTI study. OBJECTIVE: To identify measures that clinicians can use to understand the causes of walking difficulties in older persons. DESIGN: A population-based study of persons living in the Chianti geographic area (Tuscany, Italy). PARTICIPANTS: 1,453 persons (age-range 20-102 years; 91.6% of the eligible) selected from city registry of Greve in Chianti and Bagno a Ripoli (Tuscany, Italy), using a multistage sampling method. MEASUREMENTS: Factors that influence walking ability were classified into six main physiologic subsystems: central nervous system, perceptual system, peripheral nervous system, muscles, bone/joints, and energy production/delivery. Measures of the integrity and functioning of each of these proposed subsystems were identified and administered to all participants. CONCLUSIONS: Data collected in InCHIANTI will be used to identify the main risk factors that influence loss of the ability to walk in older persons, to define physiologic subsystems that are critical for walking, to select the best measures of their integrity, and to establish critical ranges in these measures that are compatible with "normal" walking ability. The final goal is to translate epidemiological research into a geriatric clinical tool that makes possible more precise diagnosis and more effective treatment in patients with walking dysfunction.

Activities of Daily Living↗
PubMed2000

Skeletal muscle mass and muscle strength in relation to lower-extremity performance in older men and women.

OBJECTIVE: Low muscle strength is associated with poorer physical function, but limited empirical evidence is available to prove the relationship between muscle mass and physical function. We tested the hypothesis that persons with lower muscle mass or muscle strength have poorer lower-extremity performance (LEP). DESIGN: A cross-sectional, population-based study. PARTICIPANTS: A cohort of 449 men and women aged 65 years and older living in Amsterdam and its surroundings participating in the second examination (1995-1996) of the Longitudinal Aging Study Amsterdam. MEASUREMENTS: Leg skeletal muscle mass was measured using dual-energy X-ray absorptiometry (DXA). Grip strength was used as an indicator of muscle strength. Timed functional performance tests, including walking and repeated chair stands, were used to assess LEP. RESULTS: After adjustment for body height and age, leg muscle mass was positively associated with LEP in men (regression coefficient 0.178 [95% confidence interval 0.013-0.343], P = .035). In women an inverse association was observed, which became positive after additional adjustment for body mass index (BMI) (0.202 [-0.001-0.405], P = .052). Grip strength was positively associated with LEP in men and women. After additional adjustment for behavioral, physiological, and psychological variables, the associations between leg muscle mass and LEP disappeared, whereas grip strength remained to be independently associated with LEP in men (0.079 [0.042-0.116], P = .0001), with a tendency in women (0.046 [-0.009-0.101], P = .11). Results were similar when quartiles of leg muscle mass or grip strength were used. CONCLUSIONS: These results suggest that low muscle strength, but not low muscle mass, is associated with poor physical function in older men and women. However, prospective studies are needed to investigate the association between loss of muscle mass and physical function.

Absorptiometry, Photon↗
PubMed2000

Characteristics of nondisabled older persons who perform poorly in objective tests of lower extremity function.

OBJECTIVES: It has been suggested that nondisabled older persons with poor performance of lower extremity function are ideal targets for interventions of disability prevention. However, health-related factors associated with poor performance are largely unknown. Using data from a representative sample of nondisabled older persons, this study identifies the diseases and biological markers that characterize this group of the population. DESIGN AND PARTICIPANTS: A total of 3,381 persons aged 71 or older, interviewed and administered a battery of physical performance tests at the sixth annual follow-up of the Established Populations for Epidemiologic Studies of the Elderly (EPESE), who reported no need for help in walking 1/4 mile or climbing stairs. MEASUREMENTS: Lower extremity performance was measured using a short battery of tests including assessment of standing balance, a timed 2.4-m walk, and timed test of rising 5 times from a chair. Chronic conditions were ascertained as self-report of a physician diagnosis. Data on previous hospitalizations were obtained from the Medicare database. Nonfasting blood samples were obtained and processed with standard methods. RESULTS: In a multivariate analysis, older age, female gender, higher BMI, history of hip fracture and diabetes, one or more hospital admissions for acute infection in the last 3 years, lower levels of hemoglobin and albumin, and higher leukocytes and gamma-glutamyl transferase were all associated independently with poor performance. CONCLUSIONS: Screening for older patients who are not disabled but have poor lower extremity performance selects a subgroup of the population with a high percentage of women, high prevalence of diabetes and hip fracture, and high levels of biological markers of inflammation. This group represents about 10% of the US population 70 to 90 years old. These findings should be considered in planning specifically tailored interventions for disability prevention in this subgroup.

Activities of Daily Living↗
PubMed2000

The prevalence of functional limitations and disability in older persons in the US: data from the National Health and Nutrition Examination Survey III.

OBJECTIVE: To provide estimates by sex and age and by sex and race/ethnicity of the proportion of older Americans who have difficulty with functional limitations and daily activities. SETTING: The Third National Health and Nutrition Examination Survey (NHANES III) 1988-1994. DESIGN: A cross-sectional nationally representative survey. PARTICIPANTS: All persons aged 60 and older who completed a household interview (N = 6,866) during NHANES III (conducted 1988-1994). MEASUREMENTS: The self-reported physical and functional disability questions from NHANES III included: lower-extremity function, instrumental activities of daily living, basic activities of daily living, needing help with personal and routine daily activities, and use of assistive devices for walking. RESULTS: Non-Hispanic black and Mexican-American men and women generally reported significantly (P < .01) more disability than did non-Hispanic white men and women. Disability was greater for minority women than for men. For both men and women, the prevalence in disability increased significantly (P < .01) with age for each measure. CONCLUSIONS: These sex-age and sex-race/ethnicity national estimates of disability indicate that minority women may represent a vulnerable subpopulation.

Activities of Daily Living↗
PubMed2000

Reliability and prevalence of physical performance examination assessing mobility and balance in older persons in the US: data from the Third National Health and Nutrition Examination Survey.

OBJECTIVE: This report provides reliability and prevalence estimates by sex, age, and race/ethnicity of an observed physical performance examination (PPE) assessing mobility and balance. SETTING: The Third National Health and Nutrition Examination Survey (NHANES III) 1988-1994. DESIGN: A cross-sectional nationally representative survey. PARTICIPANTS: All persons aged 60 and older (n = 5,403) who performed the PPE either in the mobile examination center (MEC) or in the home during NHANES III (conducted 1988-1994). MEASUREMENTS: The PPE included timed chair stand, full tandem stand, and timed 8-foot walk. RESULTS: Timed chair stand and 8-foot timed walk were reliable measurements (Intraclass Correlations > 0.5). Women were significantly slower (P < .001) than men for both timed chair stands and timed walk. Non-Hispanic white men and women did the maneuvers in significantly less time than non-Hispanic black men and women and Mexican Americans women (P < .001). CONCLUSIONS: Lower extremity functions measured by timed chair stand and walk are reliable. Women at every age group were more physically limited than men.

Activities of Daily Living↗
PubMed2000

Waist circumference and sagittal diameter reflect total body fat better than visceral fat in older men and women. The Health, Aging and Body Composition Study.

The validity of waist circumference and sagittal diameter as surrogate measures of visceral fat were assessed using preliminary cross-sectional data from the Health, Aging and Body Composition Study, a cohort of 3,075 men and women aged 70-79. Weight, body mass index, waist circumference, waist/thigh ratio, and sagittal diameter were compared by correlation, graphical analysis, and regression to total body fat as measured by dual-energy X-ray absorptiometry (Hologic 4500A), and to visceral fat area as measured by computerized tomography. We included 2,830 persons, 1,439 women and 1,391 men with complete data on all measurements. For both men and women, all measurements were strongly correlated with both total body fat and visceral fat except the waist/thigh ratio. However, waist circumference, sagittal diameter, weight, and body mass index were more closely related to total body fat than to visceral fat area (R2 for the linear regression of waist circumference on total body fat was 0.69 in women and men; R2 for linear regression of waist circumference on visceral fat area was 0.40 in women, and 0.49 in men). These data suggest that the contribution of visceral fat to health risks will be better assessed by directly measuring this fat depot.

Adipose Tissue↗
PubMed2000

American Diabetes Association diabetes diagnostic criteria, advancing age, and cardiovascular disease risk profiles: results from the Third National Health and Nutrition Examination Survey.

OBJECTIVE: To evaluate age-specific effects on diabetes prevalence estimates resulting from the American Diabetes Association (ADA) recommendation against use of the oral glucose tolerance test (OGTT), we contrasted the prevalence of two mutually exclusive groups: undiagnosed diabetes according to ADA criteria (no report of diabetes and fasting glucose [FG] > or =126 mg/dl) and isolated postchallenge hyperglycemia (IPH) (FG <126 mg/dl and OGTT > or =200 mg/dl), a group designated to have diabetes by World Health Organization (WHO) criteria but not ADA criteria. RESEARCH DESIGN AND METHODS: The weighted age-specific ratios of undiagnosed diabetes:IPH were calculated for 2,844 subjects aged 40-74 years without reported diabetes who had both FG and OGTT. A ratio > 1.0 indicated that the proportion of undiagnosed diabetes was greater than that of IPH. Mean levels of HbA1c and cardiovascular disease (CVD) risk factors were contrasted among people with undiagnosed diabetes and IPH and those without either abnormality ("nondiabetic"). RESULTS: Both undiagnosed diabetes and IPH increased with age, but age-specific undiagnosed diabetes:IPH ratios decreased from 5.49 in the 40-44 age-group to 0.77 in the 70-74 age-group. Regression analysis showed a significant (P = 0.006) negative association between age and these ratios. Mean HbA1c was 7.1% in the undiagnosed diabetes group and differed significantly from that of the IPH and nondiabetic groups (5.6 and 5.3%, respectively). Individuals with undiagnosed diabetes had less favorable triglycerides, BMI, and HDL cholesterol compared with people with IPH. CONCLUSIONS: Compared with WHO criteria, the ADA criteria underestimate glucose abnormalities more with increasing age. However, compared to those with undiagnosed diabetes, individuals with IPH had a mean HbA1c level that is considered in the nondiabetic range, and this group had significantly more favorable levels of several key CVD risk factors. These findings suggest that the ADA criteria, although underestimating the abnormalities of postchallenge hyperglycemia that occur frequently with increasing age, appear to be effective at identifying a group of individuals with both unfavorable CVD risk factor profiles and evidence of long-term exposure to hyperglycemia.

Adult↗
PubMed2000

Reexamining the sarcopenia hypothesis. Muscle mass versus muscle strength. Health, Aging, and Body Composition Study Research Group.

The association of muscle mass and muscle strength with lower-extremity performance, as measured by timed repeated chair stands, was investigated using preliminary data from 3,075 Black and White participants (70-79 years old) in the Health, Aging, and Body Composition Study. Leg muscle mass (LM) was measured by dual-energy X-ray absorptiometry (Hologic QDR 4500). The maximal isokinetic torque of the leg extensors (LS) was measured at 60 degrees/s using a Kin-Com isokinetic dynamometer. Men were stronger, had greater LM, and better performance than women. As expected, low LS was associated with poorer performance after adjusting for race, study site, and body fat. Low LM was associated with poorer performance in men and women, with a potential threshold effect in women only. When LS and LM were modeled simultaneously, only LS remained independently associated with performance. In conclusion, muscle strength, but not muscle mass, is independently associated with lower-extremity performance.

Absorptiometry, Photon↗
PubMed1999

Elevated C-reactive protein levels in overweight and obese adults.

CONTEXT: Human adipose tissue expresses and releases the proinflammatory cytokine interleukin 6, potentially inducing low-grade systemic inflammation in persons with excess body fat. OBJECTIVE: To test whether overweight and obesity are associated with low-grade systemic inflammation as measured by serum C-reactive protein (CRP) level. DESIGN AND SETTING: The Third National Health and Nutrition Examination Survey, representative of the US population from 1988 to 1994. PARTICIPANTS: A total of 16616 men and nonpregnant women aged 17 years or older. MAIN OUTCOME MEASURES: Elevated CRP level of 0.22 mg/dL or more and a more stringent clinically raised CRP level of more than 1.00 mg/dL. RESULTS: Elevated CRP levels and clinically raised CRP levels were present in 27.6% and 6.7% of the population, respectively. Both overweight (body mass index [BMI], 25-29.9 kg/m2) and obese (BMI, > or =30 kg/m2) persons were more likely to have elevated CRP levels than their normal-weight counterparts (BMI, <25 kg/m2). After adjustment for potential confounders, including smoking and health status, the odds ratio (OR) for elevated CRP was 2.13 (95% confidence interval [CI], 1.56-2.91) for obese men and 6.21 (95% CI, 4.94-7.81) for obese women. In addition, BMI was associated with clinically raised CRP levels in women, with an OR of 4.76 (95% CI, 3.42-6.61) for obese women. Waist-to-hip ratio was positively associated with both elevated and clinically raised CRP levels, independent of BMI. Restricting the analyses to young adults (aged 17-39 years) and excluding smokers, persons with inflammatory disease, cardiovascular disease, or diabetes mellitus and estrogen users did not change the main findings. CONCLUSION: Higher BMI is associated with higher CRP concentrations, even among young adults aged 17 to 39 years. These findings suggest a state of low-grade systemic inflammation in overweight and obese persons.

Adult↗
PubMed1999

Associations of elevated interleukin-6 and C-reactive protein levels with mortality in the elderly.

PURPOSE: To investigate whether interleukin-6 and C-reactive protein levels predict all-cause and cause-specific mortality in a population-based sample of nondisabled older people. SUBJECTS AND METHODS: A sample of 1,293 healthy, nondisabled participants in the Iowa 65+ Rural Health Study was followed prospectively for a mean of 4.6 years. Plasma interleukin-6 and C-reactive protein levels were measured in specimens obtained from 1987 to 1989. RESULTS: Higher interleukin-6 levels were associated with a twofold greater risk of death [relative risk (RR) for the highest quartile (> or = 3.19 pg/mL) compared with the lowest quartile of 1.9 [95% confidence interval, CI, 1.2 to 3.1]). Higher C-reactive protein levels (> or = 2.78 mg/L) were also associated with increased risk (RR = 1.6; CI, 1.0 to 2.6). Subjects with elevation of both interleukin-6 and C-reactive protein levels were 2.6 times more likely (CI, 1.6 to 4.3) to die during follow-up than those with low levels of both measurements. Similar results were found for cardiovascular and noncardiovascular causes of death, as well as when subjects were stratified by sex, smoking status, and prior cardiovascular disease, and for both early (<2.3 years) and later follow-up. Results were independent of age, sex, body mass index, and history of smoking, diabetes, and cardiovascular disease, as well as known indicators of inflammation including fibrinogen and albumin levels and white blood cell count. CONCLUSIONS: Higher circulating levels of interleukin-6 and C-reactive protein were associated with mortality in this population-based sample of healthy older persons. These measures may be useful for identification of high-risk subgroups for anti-inflammatory interventions.

Aged↗
PubMed1999

The relationship between body composition and physical performance in older women.

BACKGROUND: The relationship between age-associated change in body composition and physical disability is still unknown. Skeletal muscle mass declines with age in both sexes; however, since women have less muscle mass per unit of weight than men, these changes may be more debilitating in women. OBJECTIVE: To evaluate the relationship between body composition and physical performance. DESIGN: A cross-sectional study. PARTICIPANTS: 144 women aged 68 to 75 were selected randomly from the general population of Verona. MEASUREMENTS: Body composition was evaluated using dual energy X-ray absorptiometry and bioimpedance. Physical performance was evaluated using a modified version of the Activities of Daily Living scale. Distance walked in 6 minutes was calculated, and isometric knee strength was tested. RESULTS: Normal women had a significantly lower body mass index (BMI) and percent body fat. These women also had a higher ratio of body cell mass (BCM) and total fat free mass (FFM) than women with physical impairments. After adjusting for BMI, women in the lowest tertile of muscle strength had significantly lower BCM than those in the highest tertile. CONCLUSIONS: These cross-sectional data show that although muscle strength is related to fat-free mass, disability in older women is associated with heavier BMI and with a higher percentage of body fat.

Absorptiometry, Photon↗
PubMed1999

Serum IL-6 level and the development of disability in older persons.

BACKGROUND: The serum concentration of interleukin 6 (IL-6), a cytokine that plays a central role in inflammation, increases with age. Because inflammation is a component of many age-associated chronic diseases, which often cause disability, high circulating levels of IL-6 may contribute to functional decline in old age. We tested the hypothesis that high levels of IL-6 predict future disability in older persons who are not disabled. METHODS: Participants at the sixth annual follow-up of the Iowa site of the Established Populations for Epidemiologic Studies of the Elderly aged 71 years or older were considered eligible for this study if they had no disability in regard to mobility or in selected activities of daily living (ADL), and they were re-interviewed 4 years later. Incident cases of mobility-disability and of ADL-disability were identified based on responses at the follow-up interview. Measures of IL-6 were obtained from specimens collected at baseline from the 283 participants who developed any disability and from 350 participants selected randomly (46.9%) from those who continued to be non-disabled. FINDINGS: Participants in the highest IL-6 tertile were 1.76 (95% CI, 1.17-2.64) times more likely to develop at least mobility-disability and 1.62 (95% CI, 1.02-2.60) times more likely to develop mobility plus ADL-disability compared with to the lowest IL-6 tertile. The strength of this association was almost unchanged after adjusting for multiple confounders. The increased risk of mobility-disability over the full spectrum of IL-6 concentration was nonlinear, with the risk rising rapidly beyond plasma levels of 2.5 pg/mL. INTERPRETATION: Higher circulating levels of IL-6 predict disability onset in older persons. This may be attributable to a direct effect of IL-6 on muscle atrophy and/or to the pathophysiologic role played by IL-6 in specific diseases.

Activities of Daily Living↗
PubMed1999

Validity of fan-beam dual-energy X-ray absorptiometry for measuring fat-free mass and leg muscle mass. Health, Aging, and Body Composition Study--Dual-Energy X-ray Absorptiometry and Body Composition Working Group.

The aim of the study was to examine the accuracy of fan-beam dual-energy X-ray absorptiometry (DEXA) for measuring total body fat-free mass (FFM) and leg muscle mass (MM) in elderly persons. Participants were 60 men and women aged 70-79 yr and with a body mass index of 17.5-39.8 kg/m(2). FFM and MM at four leg regions were measured by using DEXA (Hologic 4500A, v8.21). A four-compartment body composition model (4C) and multislice computed tomography (CT) of the legs were used as the criterion methods for FFM and MM, respectively. FFM by DEXA was positively associated with FFM by 4C (R(2) = 0.98, SE of estimate = 1.6 kg). FFM by DEXA was higher [53.5 +/- 12.0 (SD) kg] than FFM by 4C (51.6 +/- 11.9 kg; P < 0.001). No association was observed between the difference and the mean of the two methods. MM by DEXA was positively associated with CT at all four leg regions (R(2) = 0.86-0.96). MM by DEXA was higher than by CT in three regions. The results of this study suggest that fan-beam DEXA offers considerable promise for the measurement of total body FFM and leg MM in elderly persons.

Absorptiometry, Photon↗