Biomedical subjects
S Owens
Publications and source records attributed to S Owens.
Prediction of visceral adipose tissue from simple anthropometric measurements in youths with obesity.
OBJECTIVE: Although visceral adipose tissue (VAT) is the component of body composition most highly associated with cardiovascular risk factors, its measurement requires expensive procedures, such as magnetic resonance imaging. This study examined the ability of simple demographic and anthropometric measurements to predict magnetic resonance imaging-derived VAT in 76 apparently healthy, black and white youths with obesity who were 7 years to 16 years of age. RESEARCH METHODS AND PROCEDURES: Stepwise multiple linear regression was used to develop a prediction equation for VAT based on 13 simple anthropometric variables (height, weight, body mass index, triceps skinfold, calf skinfold, sagittal diameter, waist circumference, hip circumference, thigh circumference, waist/hip ratio, waist/thigh ratio, sagittal diameter/thigh ratio, and percent body fat from the sum of calf and triceps skinfolds) and three demographic variables (age, gender and ethnicity). RESULTS: The stepwise multiple regression procedure yielded a final model that included two anthropometric variables (sagittal diameter and waist/hip ratio) and one demographic variable (ethnicity). The prediction equation was: VAT = - 124.06+ 16.67 (ethnicity)+4.15 (sagittal diameter)+100.89 (waist/hip ratio), where ethnicity was coded as 0= black and 1 = white. The model explained 63% of the variance in VAT and was associated with a measurement error of 23.9%. DISCUSSION: Although the model seems to lack sufficient explanatory power for routine use in clinical settings with individual patients, it may have some utility in epidemiological studies given its relatively small (<25%) standard error of estimate.
Effect of physical training and its cessation on percent fat and bone density of children with obesity.
OBJECTIVE: We determined the effect of 4-month periods of physical training (PT) and detraining on percent fat (percent fat) and bone density of children with obesity. RESEARCH METHODS AND PROCEDURES: Subjects were 79 7- to 11-year-old children with obesity; 34 were white, 44 were black, and 1 was Asian, 26 were male and 53 were female. They were randomly assigned to two groups: group 1 engaged in PT for the first 4 months, while group 2 engaged in PT during the second 4 months. Body composition was measured with dual energy absorptiometry, and diet was measured with 4 days of recall for each 4-month period. PT was offered 5 days/week for 40 minutes/session, heart rate monitors were worn, and no dietary information was given; mean attendance was 80%, and mean heart rate per session was 157 bpm. RESULTS: Group by time interactions across the three time-points (from analysis of variance) were significant for percent fat (p = <0.001) and bone density (p = 0.045). Both groups declined in percent fat during the periods of PT, by an average of 1.6% fat units; in the 4 months after cessation of PT, group 1 increased by 1.3% fat. In both groups, bone density increased more during periods of PT (0.025 g/cm2) than during periods of no PT (0.010 g/cm2). No significant PT vs. no-PT differences were found for dietary intake of energy, macronutrients, or calcium. DISCUSSION: This study suggests that regular exercise, without dietary intervention, can enhance the body composition of children with obesity.
Effects of exercise training and its cessation on components of the insulin resistance syndrome in obese children.
OBJECTIVE: To determine the effect of exercise training (ET) on components of the insulin resistance syndrome (IRS) in obese children. DESIGN: Randomized, modified cross-over study, with subjects assigned to one of two conditions: (1) 4 months of ET followed by 4 months of no-ET; or (2) 4 months of no-ET followed by 4 months of ET. Measurements were made at three time points: 0, 4 and 8 months. SUBJECTS: 79 obese, but otherwise healthy children (age: 7-11 y, percent fat (%fat) 27-61%). MEASUREMENTS: Plasma lipid and lipoprotein concentrations, plasma insulin and glucose concentrations; %fat; submaximal heart rate (HR) as an index of fitness. EXERCISE TRAINING: ET was offered 5 d/week 40 min/d. For the 73 children who completed 4 months of ET, the mean attendance was 80% (that is, 4 d/week) and the average HR during ET was 157 bpm. RESULTS: Significant (P < 0.05) group x time interactions were found for plasma triglyceride (TG) and insulin concentrations and %fat. The average change for both groups, from just before ET to just after the 4 month ET was -0.24 mmol.l-1 for TG, -25.4 pmol.l-1 for insulin and -1.6 units for %fat. When Group 1 ceased ET, over the following 4 month period the average change for insulin was +26.6 pmol.l-1 and for %fat +1.3 units. CONCLUSION: Some components (plasma TG, insulin, %fat) of the IRS are improved as a result of 4 months of ET in obese children. However, the benefits of ET are lost when obese children become less active.
Description and process evaluation of a physical training program for obese children.
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Plasma leptin concentrations in obese children: changes during 4-mo periods with and without physical training.
BACKGROUND: Little is known about the effects of physical training on plasma leptin concentrations in children. OBJECTIVE: We sought to determine the effects of 4-mo periods with and without physical training on leptin in obese children and to explore the determinants of leptin at baseline and in response to physical training. DESIGN: Participants were 34 obese 7-11-y-old children randomly assigned to engage in physical training during either the first or second 4 mo of the 8-mo study. RESULTS: Total body composition, visceral adiposity, and insulin were all positively correlated with leptin at baseline (P < or = 0.05); however, only fat mass was retained in the final stepwise regression (P = 0.0001, R2 = 0.57). Leptin decreased during the 4-mo periods of physical training and increased in the 4 mo after cessation of physical training (P < 0.001 for the time by group interaction). Decreases in leptin were greatest in children with higher pretraining leptin concentrations, those whose total mass increased least, and those whose insulin concentrations decreased most (P < or = 0.05); only pretraining leptin concentration (P = 0.009) and change in total mass (P = 0.0002) were retained in the final regression (R2 = 0.53). CONCLUSIONS: In obese children, leptin concentration decreased during 4 mo of physical training and increased during a subsequent 4-mo period without physical training, fat mass was highly correlated with baseline leptin, and greater reductions in leptin during 4 mo of physical training were seen in children with higher pretraining leptin and in those whose total mass increased least.
Correlates of individual differences in body-composition changes resulting from physical training in obese children.
BACKGROUND: No studies have been reported in children that assess correlates of body-composition changes in response to a physical training intervention. OBJECTIVE: The hypothesis studied was that variation in diet and physical activity would explain a significant portion of the interindividual variation in the response of body composition to physical training. DESIGN: The participants were 71 obese children aged 7-11 y (22 boys, 49 girls; 31 whites, 40 blacks). Body composition was measured by dual-energy X-ray absorptiometry, physical activity by a 7-d recall interview, and diet by two, 2-d recalls. The children underwent 4 mo of physical training. RESULTS: The mean attendance was 4 d/wk, the mean (+/-SD) heart rate for the 40-min sessions was 157 +/- 7 beats/min, and the mean energy expenditure was 946 +/- 201 kJ/session. On average, the percentage body fat decreased significantly in the total group, and total mass, fat-free soft tissue, bone mineral content, and bone mineral density increased, but there was a good deal of individual variability. Multiple regression models indicated that in general, more frequent attendance, being a boy, lower energy intake, and more vigorous activity were associated with healthier body-composition changes with physical training. Ethnicity was not retained as a correlate of the change of any component of body composition. CONCLUSIONS: In obese children, age, vigorous activity, diet, and baseline percentage body fat together accounted for 25% of the variance in the change in percentage body fat with physical training.
Effects of physical training and its cessation on the hemostatic system of obese children.
BACKGROUND: Physical training can improve hemostatic function in adults, thereby reducing heart disease risk, but no information is available in children on whether physical training can enhance hemostatic function. OBJECTIVE: The purpose of this investigation was to examine the effects of a physical training program on hemostatic variables in a biethnic group of obese children. DESIGN: Children were randomly assigned to 2 groups. Group 1 participated in physical training for 4 mo and then ceased physical training for 4 mo, whereas group 2 did no physical training for the first 4 mo and then participated in physical training for 4 mo. Plasma hemostatic variables [fibrinogen, plasminogen activator inhibitor 1 (PAI-1), and D-dimer) were measured at months 0, 4, and 8. RESULTS: Analyses of variance revealed no significant group-by-time interactions for the hemostatic variables. When data from both groups were combined there was a significant decrease in D-dimer after 4 mo of physical training (P < 0.05). Factors explaining individual differences in responsiveness to the physical training revealed that individuals with greater percentage fat before physical training showed greater reductions in fibrinogen and D-dimer, and that blacks showed greater reductions in D-dimer than whites (P < 0.05). Stepwise multiple linear regression showed that only higher prephysical training concentrations of fibrinogen, PAI-1, and D-dimer explained significant proportions of the variation in changes in these variables. CONCLUSIONS: In obese children, 4-mo periods of physical training did not lead to significant changes in hemostatic variables. Children with greater adiposity and concentrations of hemostatic factors before physical training showed greater reductions in hemostatic variables after physical training than did children with lesser values.
Effect of physical training on total and visceral fat in obese children.
PURPOSE: Children with high levels of total body fat mass (TFM) and visceral adipose tissue (VAT) have elevated levels of certain risk factors for coronary artery disease and non-insulin-dependent diabetes mellitus. We tested the hypothesis that controlled physical training, without dietary intervention, would have a favorable impact on VAT and percent body fat (%BF) in obese children. METHODS: A volunteer sample of 74 obese children, 7-11 yr of age, accepted random assignment to physical training or control groups. Before and after 4 months of intervention, measurements were obtained for VAT, TFM, %BF, daily physical activity, and cardiovascular fitness. The intervention involved 4 months of controlled physical training 5 d x wk(-1), 40 min per session, at a mean heart rate (HR) of 157 beats x min(-1). The estimated energy expenditure (EE) per training session was 925+/-201 kJ. RESULTS: Compared with the control group, the physical training group declined significantly in %BF (delta = -2.2%) (P < 0.01), TFM (delta = -3.1%) (P < 0.01), and subcutaneous abdominal adipose tissue (delta = - 16.1%) (P < 0.05), and increased significantly in fat-free mass (delta = +6.1%) (P < 0.05) and moderate-to-very hard physical activity (delta = +14.1%) (P < 0.05). The increase in VAT was significantly less in the physical training group (delta = +0.5%) as compared with that in the control group (delta = +8.1%) (P < 0.05). CONCLUSIONS: This study showed that during physical training obese children: 1) were capable of participating in a substantial amount of high intensity physical training over a 4-month period: 2) accumulated significantly less VAT as compared with nonexercising controls; and 3) experienced other beneficial changes in total and regional body composition.
Chronic compartment syndrome affecting the lower limb: MIBI perfusion imaging as an alternative to pressure monitoring: two case reports.
Intracompartmental pressure monitoring remains the primary method of diagnosing chronic compartment syndrome. MIBI perfusion imaging is widely available and offers a radionuclear imaging technique for diagnosing this condition. Although the results are not identical with those from pressure monitoring, MIBI may offer a useful screening test for this condition.
Visceral adipose tissue and cardiovascular risk factors in obese children.
OBJECTIVE: In adults visceral adipose tissue (VAT) has been shown to be more highly correlated with cardiovascular (CV) risk factors than are other measures of adiposity such as subcutaneous abdominal adipose tissue (SAAT), percent body fat (%BF), or total body fat mass (TFM). We examined the relations between these measures of fatness and CV risk factors in obese children. STUDY DESIGN: Subjects were 64 obese (27% to 61% BF) children (24 black girls, 19 white girls, 11 black boys, 10 white boys) aged 7 to 11 years. VAT and SAAT were measured with magnetic resonance imaging. TFM and %BF were determined with dual x-ray absorptiometry. Hierarchical stepwise multiple regression analyses were used to determine the proportions of variance in CV risk factors explained by the demographic and adiposity measures. RESULTS: VAT but not SAAT, %BF, or TFM explained a significant proportion of the variance (r2 range = 0.10 to 0.21) in several lipid/lipoprotein risk factors including triacylglycerols, high-density lipoprotein cholesterol, the ratio of total cholesterol to high-density lipoprotein cholesterol, and low-density lipoprotein particle size. CONCLUSION: Many of the deleterious relations between VAT and lipid/lipoprotein risk factors seen in adults were already present in this sample of obese children.
Relations of body composition to left ventricular geometry and function in children.
OBJECTIVE: To determine whether body composition and fasting insulin levels explained variation in left ventricular (LV) function and geometry. PARTICIPANTS: Sixty-two children, 7 to 13 years of age. RESULTS: For LV mass/height the partial correlation (age controlled) with percentage of fat was r = 0.34 (p = 0.008) and the correlation with (Ln)insulin was r = 0.25 (p = 0.051); multiple regression showed that independent proportions of the variance were explained by gender (boys > girls), ethnicity (black > white subjects), and percentage of fat (p = 0.015). Nonnormalized LV mass was correlated (age controlled) with fat-free mass (r = 0.76; p < 0.001), fat mass (r = 0.58; p < 0.001), and (Ln) insulin (r = 0.27; p = 0.0359); multiple regression showed that fat-free mass and fat mass explained independent proportions of the variance. Percentage of fat was correlated (age controlled) with greater relative wall thickness (r = 0.34; p = 0.008) and lower midwall fractional shortening (-0.37; p = 0.004). CONCLUSION: Body fatness was cross-sectionally associated with levels of LV function and geometry that in adults have been found to lead to morbidity and death. The relationship of fatness to LV mass may be due to the higher insulin concentrations in the fatter children. These cross-sectional results are consistent with the hypothesis that excess fatness may adversely influence cardiovascular health early in life.
Radiotherapy for age-related macular degeneration.
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A randomized, double-blind trial of valaciclovir prophylaxis for cytomegalovirus disease in patients with advanced human immunodeficiency virus infection. AIDS Clinical Trials Group Protocol 204/Glaxo Wellcome 123-014 International CMV Prophylaxis Study Group.
Cytomegalovirus (CMV) disease is a common complication of advanced human immunodeficiency virus (HIV) infection. Administration of oral valaciclovir, a valine ester of acyclovir, achieves sufficient plasma acyclovir levels to inhibit many clinical isolates. Acyclovir has been associated with enhanced survival in AIDS but not with CMV disease prevention. CMV-seropositive patients (1227) with CD4 cell counts <100/mm3 were enrolled in a randomized, double-blind trial. Valaciclovir, 8 g/day, was compared with acyclovir, 3.2 or 0.8 g/day, for CMV prevention; all three arms were compared for survival. The confirmed CMV disease rate was 11.7% among valaciclovir recipients and 17.5% in the pooled acyclovir arms, a 33% reduction in risk. Time to confirmed CMV disease was significantly longer for the valaciclovir group (P = .03). A trend toward earlier mortality for valaciclovir recipients was seen (P = .06). Toxicity and earlier medication discontinuation were more common in this group. Valaciclovir significantly reduces the risk of CMV disease. Further exploration of a better-tolerated dose is warranted.
Fat distribution and hemostatic measures in obese children.
We examined the relation of general and visceral adiposity to plasma hemostatic factors [fibrinogen, D-dimer, and plasminogen activator inhibitor 1 (PAI-1)] in obese boys and girls 7-11 y of age (n = 41). Boys had significantly greater fibrinogen and D-dimer concentrations than girls (P < 0.05). whereas blacks had significantly greater fibrinogen and D-dimer concentrations than whites (P < 0.05). Univariate analyses revealed that fibrinogen was positively associated with percentage body fat (%BF) (r = 0.42, P < 0.01), subcutaneous abdominal adipose tissue (SAAT) (r = 0.40, P < 0.01), total fat mass (r = 0.42, P < 0.01), and body mass index (r = 0.41, P < 0.01). PAI-1 was positively associated with visceral adipose tissue (VAT) (r = 0.49, P < 0.01), SAAT (r = 0.32, P < 0.05), fat-free mass (r = 0.50, P < 0.01), and insulin (r = 0.61, P < 0.001). D-Dimer was positively associated with %BF (r = 0.40, P < 0.01), SAAT (r = 0.37, P < 0.05), total fat mass (r = 0.40, P < 0.01), and body mass index (r = 0.43, P < 0.01). Multiple regression analysis revealed that for fibrinogen, sex and higher %BF explained significant independent portions of the variance. For PAI-1, higher amounts of VAT and fat-free mass were significant predictors. For D-dimer, ethnicity was a significant predictor. These results suggest that general adiposity and VAT may play a role in regulating plasma hemostatic factors in obese children. Even early in childhood, adiposity is associated with unfavorable concentrations of hemostatic factors that are in turn implicated in cardiovascular morbidity and mortality later in life.
Comparison of the safety and efficacy of the fixed combination of dorzolamide/timolol and the concomitant administration of dorzolamide and timolol: a clinical equivalence study. International Clinical Equivalence Study Group.
AIMS: To compare the tolerability and efficacy of a fixed combination solution of dorzolamide/timolol (Cosopt), administered twice daily with the concomitant administration of its components, dorzolamide (Trusopt) twice daily and timolol (Timoptic) twice daily. METHODS: After a 2 week timolol run in, patients with open angle glaucoma or ocular hypertension were randomised (1:1) to receive treatment with either the dorzolamide/timolol combination solution twice daily (combination) or the dorzolamide solution twice daily plus timolol maleate solution twice daily (concomitant) for 3 months. RESULTS: 299 patients were entered and 290 patients completed the study. Compared with the timolol baseline, additional IOP lowering of 16% was observed at trough (hour 0) and 22% at peak (hour 2) at month 3 in both the concomitant and combination groups. The IOP lowering effects of the two treatment groups were clinically and statistically equivalent as demonstrated by the extremely small point differences (concomitant--combination) observed in this study--0.01 mm Hg at trough and 0.08 mm Hg at peak. The safety variables of the concomitant and combination groups were very similar. Both combination and concomitant therapy were well tolerated and few patients discontinued due to adverse effects. CONCLUSIONS: The dorzolamide/timolol combination solution administered twice daily is equivalent in efficacy and has a similar safety profile to the concomitant administration of the components administered twice daily.
Cytomegalovirus retinitis after initiation of highly active antiretroviral therapy.
BACKGROUND: In previous natural history studies and clinical trials, AIDS-related cytomegalovirus (CMV) retinitis has occurred primarily in patients with absolute CD4 counts of 50 cells/microL or less (0.05 x 10(9)/L) at the time of diagnosis. METHODS: We report five patients identified from our clinical practices who were diagnosed with CMV retinitis while their CD4 counts were above 195 cells/microL. We also analysed, based on CD4 counts, 76 AIDS patients with newly diagnosed CMV retinitis whose CD4 lymphocyte enumerations were done in laboratories that maintained certification in a common external quality control programme. FINDINGS: 5-24 weeks before retinitis was diagnosed, all five patients had had absolute CD4 lymphocyte counts of less than 85 cells/microL, and 4-7 weeks before diagnosis, all five patients had started taking highly active antiretroviral treatment (HAART) regimens. Only one (4%) of 27 patients enrolled in the trial between July, 1995, and February, 1996, had an absolute CD4 count of more than 50 cells/microL, and none of 27 had an absolute CD4 count of more than 100/microL on entry to the trial. However, from March, 1996 (when indinavir and ritonavir were approved by the FDA for marketing in the USA), to August, 1996, 14 (29%) of 49 patients had CD4 counts of more than 50/microL and seven (14%) of 49 had a CD4 count of more than 100 cells/microL on entry. INTERPRETATION: These findings suggest that the early immunological effects of HAART may not provide sufficient protection to prevent CMV retinitis in patients who have very low CD4 counts when therapy is started. Clinicians should note that CMV retinitis may now occur in patients who have CD4 counts of more than 100 cells/microL.
Weight-independent cardiovascular fitness and coronary risk factors.
BACKGROUND: It is unclear whether cardiovascular fitness influences risk factors for coronary artery disease and non-insulin-dependent diabetes mellitus independently of level of body fat because fitness is often measured in tasks that involve moving body weight (eg, running) and because body weight and level of body fat are correlated. OBJECTIVE: To measure fitness during a task in which body weight was controlled experimentally (ie, supine cycling). DESIGN: Cross-sectional. PARTICIPANTS: Seventy-four children, 7 to 13 years of age, recruited through school flyers and newspaper advertisements, varying in level of body fat from 7% to 61%. There were 31 boys and 43 girls; 35 were white and 39 were black. MAIN INDEPENDENT VARIABLES: Cardiovascular fitness was expressed as submaximal heart rate while cycling at a power output of 49 W, and level of body fat was measured with dual x-ray absorptiometry. MAIN OUTCOME MEASURES: Blood pressure and levels of triglycerides, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, insulin, glucose, and glycohemoglobin. RESULTS: Controlling for age and sex, level of body fat was significantly (P < .01) related to unfavorable levels of systolic blood pressure (r = 0.32), triglycerides (r = 0.42), high-density lipoprotein cholesterol (r = -0.31), insulin (r = 0.50), and total cholesterol to high-density lipoprotein cholesterol ratio (r = 0.37); submaximal heart rate was not significantly correlated with any of the other variables. CONCLUSIONS: When cardiovascular fitness was measured in a weight-independent task, it was not significantly related to level of body fat or the major coronary artery disease and non-insulin-dependent diabetes mellitus risk factors. In addition, we confirmed previous findings that higher levels of body fat are associated with a very unfavorable risk profile.