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Biomedical subjects

Steven N Blair

Publications and source records attributed to Steven N Blair.

At least 19 recordsLinked to original sources
PubMed2006

Coronary artery calcium score, risk factors, and incident coronary heart disease events.

BACKGROUND: Whether the absence of coronary artery calcium, or conversely the presence of high volumes of coronary artery calcium, may alter assessment of coronary heart disease risk based on traditional risk factors is uncertain. We sought to identify a potential threshold of coronary artery calcium for clinical use and examine the predictive power of coronary artery calcium in individuals categorized using conventional coronary heart disease risk assessment. METHODS: The study included 10,746 men and women (36.3%) with a mean age of 53.8+/-9.9 years who were either physician- or self-referred for electron beam tomography scanning to a preventive medical clinic. Coronary heart disease risk factors were elicited by use of a questionnaire. RESULTS: During a mean follow-up of 3.5 years, 81 primary events (coronary heart disease death or nonfatal myocardial infarction) occurred. Among individuals with a coronary artery calcium score of zero, the primary event rate was very low (0.4 events per 1000 person-years of observation). When participants were stratified by self-reported coronary heart disease risk factors (0-2, or 3-4), a coronary artery calcium score >or=100 was associated with substantially increased risk of coronary heart disease events within each level of stratification. In a subgroup of participants with available clinical data, similar results were found when participants were categorized by Framingham risk scores. CONCLUSIONS: Coronary artery calcium score can identify individuals at increased risk for coronary heart disease events who otherwise would be considered low-risk based on clinical assessment. A coronary artery calcium score of zero is associated with very low risk for coronary heart disease in the short to intermediate term ( approximately 3.5 years) regardless of the number of risk factors present.

Adult↗
PubMed2006

Coronary artery calcium, exercise tolerance, and CHD events in asymptomatic men.

Coronary artery calcium (CAC) scores >/=100 are predictive of CHD events in asymptomatic men. Exercise tolerance of >/=10METs predicts lower event rates in CHD patients; however, its relationship with events in individuals with subclinical atherosclerosis is less known. Participants were 710 asymptomatic men from the Aerobics Center Longitudinal Study whose exercise tolerance (ET) was quantified (<10 or >/=10METs) and whose CAC score was >/=100 as measured by electron beam tomography. During 3.5 years of follow-up 59 CHD events occurred. The age-adjusted hazard ratio (HR) of CHD events was 0.26 (95% CI=0.15-0.45) in men whose ET was >/=10METs compared with men whose ET was <10METs. Adjustment for CHD risk factors and abnormal exercise ECG did not change the association between ET and CHD. The extent of underlying atherosclerosis did not influence the association between ET and CHD; for example, the HR for CHD events in the >/=10MET group among men with CAC scores <400 and >/=400 was 0.16 (95% CI=0.05-0.56) and 0.23 (95% CI=0.11-0.46), respectively. In asymptomatic men with subclinical coronary atherosclerosis, an ET of >/=10METs identifies patients at lower risk for manifest CHD.

Calcium↗
PubMed2006

Cardiorespiratory fitness, macronutrient intake, and the metabolic syndrome: the Aerobics Center Longitudinal Study.

OBJECTIVE: This study examines the cross-sectional associations between cardiorespiratory fitness and the metabolic syndrome with adjustment for macronutrient intake from 3-day dietary records. DESIGN: Cross-sectional study. SUBJECTS/SETTING: Women and men who had a comprehensive medical examination, including a symptom-limited maximal treadmill exercise test, and completed 3-day dietary records at the Cooper Clinic, Dallas, TX. MAIN OUTCOME MEASURES: Metabolic syndrome as defined by the National Cholesterol Education Program Adult Treatment Panel III criteria. STATISTICAL ANALYSES PERFORMED: Analysis of variance was used to examine differences in continuous data. General linear analysis was used to examine linear trends. Mantel-Haenszel chi(2) analyses were used to examine differences in categorical data. Logistic regression was used to estimate odds ratios and 95% confidence intervals. RESULTS: After adjusting for sex and age, cardiorespiratory fitness was inversely associated with the prevalence of metabolic syndrome (P<0.001). Adjustment for macronutrient intake and other potential confounding variables did not alter the association between cardiorespiratory fitness and prevalent metabolic syndrome. CONCLUSIONS: Cardiorespiratory fitness is inversely associated with the prevalence of metabolic syndrome. Patients should be encouraged to increase their physical activity to decrease their risk for metabolic syndrome and coronary heart disease.

Adult↗
PubMed2006

Visceral fat is an independent predictor of all-cause mortality in men.

OBJECTIVE: To examine the independent associations of abdominal fat (visceral and subcutaneous) and liver fat with all-cause mortality. RESEARCH METHODS AND PROCEDURES: Participants included 291 men [97 decedents and 194 controls; mean age, 56.4 +/- 12.0 (SD) years] who received a computed tomography (CT) examination at the preventive medicine clinic in Dallas, TX, between 1995 and 1999, with a mean mortality follow-up of 2.2 +/- 1.3 years. Abdominal fat was determined using contiguous CT images from the L3-L4 to L4-L5 intervertebral space. Liver fat was assessed using the CT-determined liver attenuation value, which is inversely related to liver fat. Logistic regression was used to determine the independent association between the fat depots and all-cause mortality. RESULTS: During the study, there were 97 deaths. Visceral fat [odds ratio (OR) per SD: 1.83; 95% CI: 1.23 to 2.73], abdominal subcutaneous fat (1.44; 1.02 to 2.03), liver fat (0.64; 0.46 to 0.87), and waist circumference (1.41; 1.01 to 1.98) were significant individual predictors of mortality after controlling for age and length of follow-up. In a model including all three fat measures (subcutaneous, visceral, and liver fat), age, and length of follow-up, only visceral fat (1.93; 1.15 to 3.23) was a significant predictor of mortality. DISCUSSION: Visceral fat is a strong, independent predictor of all-cause mortality in men.

Aged↗
PubMed2006

Association of cardiorespiratory fitness, body mass index, and waist circumference to nonalcoholic fatty liver disease.

BACKGROUND & AIMS: There is a need for more work examining the potential of physical activity and/or weight control as a preventive and/or therapeutic option in the treatment of fatty liver diseases. The purpose of this study was to examine the association between cardiorespiratory fitness, body mass index (BMI), and waist circumference with markers of nonalcoholic fatty liver disease (NAFLD). METHODS: Participants consisted of 218 apparently healthy nonsmoking, nonalcoholic men aged 33-73 years. Cardiorespiratory fitness was assessed by a maximal treadmill test. Liver and spleen density were measured using a computed tomography scan. We defined the presence of NAFLD as the following 3 conditions being met: (1) liver to spleen density of 1.0 or less, (2) serum alanine transaminase level greater than 30 U/L, and (3) serum aspartate transaminase/alanine transaminase level less than 1.0. RESULTS: Twenty-four (11%) of the participants met the NAFLD definition. There was an inverse association between fitness categories, and a positive association for BMI categories (and waist circumference categories) with the prevalence of NAFLD (P for trend <.001 for all). Fitness and BMI were independent of each other in their associations with the prevalence of NAFLD. The addition of waist circumference to the regression model attenuated the association with prevalence of NAFLD for both fitness (P value changed from <.0001 to .06) and BMI (P value changed from <.001 to .22). CONCLUSIONS: Fitness (inversely) and BMI (directly) were associated with the prevalence of NAFLD. However, these associations were attenuated when abdominal obesity was included in the statistical model.

Adult↗
PubMed2006

Effects of a physical activity intervention on measures of physical performance: Results of the lifestyle interventions and independence for Elders Pilot (LIFE-P) study.

BACKGROUND: The Short Physical Performance Battery (SPPB), which includes walking, balance, and chair stands tests, independently predicts mobility disability and activities of daily living disability. To date, however, there is no definitive evidence from randomized controlled trials that SPPB scores can be improved. Our objective was to assess the effect of a comprehensive physical activity (PA) intervention on the SPPB and other physical performance measures. METHODS: A total of 424 sedentary persons at risk for disability (ages 70-89 years) were randomized to a moderate-intensity PA intervention or a successful aging (SA) health education intervention and were followed for an average of 1.2 years. RESULTS: The mean baseline SPPB score on a scale of 0-12, with 12 corresponding to highest performance, was 7.5. At 6 and 12 months, the PA versus SA group adjusted SPPB (+/- standard error) scores were 8.7 +/- 0.1 versus 8.0 +/- 0.1, and 8.5 +/- 0.1 versus 7.9 +/- 0.2, respectively (p < .001). The 400-meter walking speed was also significantly improved in the PA group. The PA group had a lower incidence of major mobility disability defined as incapacity to complete a 400-meter walk (hazard ratio = 0.71, 95% confidence interval = 0.44-1.20). CONCLUSIONS: A structured PA intervention improved the SPPB score and other measures of physical performance. An intervention that improves the SPPB performance may also offer benefit on more distal health outcomes, such as mobility disability.

Activities of Daily Living↗
PubMed2006

Physical activity, cardiorespiratory fitness, and adiposity: contributions to disease risk.

PURPOSE OF REVIEW: To discuss assessing physical activity, cardiorespiratory fitness, and adiposity in the context of examining their prospective joint associations with mortality in cohort studies. RECENT FINDINGS: Accurate and comprehensive assessment of free-living physical activity patterns and related energy expenditure is difficult. Cardiorespiratory fitness is a reproducible measure associated with recent physical activity patterns; however, its assessment has been considered impractical in epidemiologic studies. Likewise, objective measures of adiposity and fat distribution often are not feasible in large studies. Thus, physical activity and adiposity exposures typically are quantified using self-reports of physical activity habits and of height and weight to compute body mass index. When considered jointly, adults with higher levels of fitness or reported physical activity tend to have lower mortality risk than their unfit and inactive peers within the same body mass index group. SUMMARY: Accumulating evidence suggests that higher physical activity or fitness attenuates the health risks of obesity. Available data largely are based on crude measures of physical activity and body habitus, which may obscure their association with disease risk. Accurate measures must be included in epidemiologic studies to improve estimation of the independent and joint associations of these exposures with health outcomes.

Adipose Tissue↗
PubMed2006

The importance of waist circumference in the definition of metabolic syndrome: prospective analyses of mortality in men.

OBJECTIVE: The purpose of this study was to compare the predictive ability of the National Cholesterol Education Panel (NCEP), revised NCEP (NCEP-R), and International Diabetes Federation (IDF) metabolic syndrome criteria for mortality risk, and to examine the effects of waist circumference on mortality within the context of these criteria. RESEARCH DESIGN AND METHODS: The sample included 20,789 white, non-Hispanic men 20-83 years of age from the Aerobics Center Longitudinal Study. The main outcome measures were all-cause and cardiovascular disease (CVD) mortality over 11.4 years of follow-up. RESULTS: The proportions of men with the metabolic syndrome were 19.7, 27, and 30% at baseline, respectively, according to NCEP, NCEP-R, and IDF criteria. A total of 632 deaths (213 CVD) occurred. The relative risks (RRs) and 95% CIs of all-cause mortality were 1.36 (1.14-1.62), 1.31 (1.11-1.54), and 1.26 (1.07-1.49) for the NCEP, NCEP-R, and IDF definitions, respectively. The corresponding RRs for CVD mortality were 1.79 (1.35-2.37), 1.67 (1.27-2.19), and 1.67 (1.27-2.20). Additionally, there was a significant trend for a higher risk of CVD mortality across waist circumference categories (<94, 94-102, and >102 cm) among men with at least two additional metabolic syndrome risk factors (P = 0.01). CONCLUSIONS: The prediction of mortality with IDF and NCEP metabolic syndrome criteria was comparable in men. Waist circumference is a valuable component of metabolic syndrome; however, the IDF requirement of an elevated waist circumference warrants caution given that a large proportion of men with normal waist circumference have multiple risk factors and an increased risk of mortality.

Adult↗
PubMed2006

Does measurement site for visceral and abdominal subcutaneous adipose tissue alter associations with the metabolic syndrome?

OBJECTIVE: To determine whether the associations between visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue (ASAT), and the metabolic syndrome are altered depending on measurement site for VAT and ASAT and the definition used to identify the metabolic syndrome. RESEARCH DESIGN AND METHODS: Total VAT and ASAT volume was derived using approximately 37 contiguous computed tomography (CT) images from T10-T11 to L5-S1 in 85 men. CT images obtained at eight intervertebral locations (e.g., L4-L5, L3-L4, etc.) were used to determine the associations between partial volumes (single images) and metabolic syndrome. Metabolic syndrome was defined using the National Cholesterol Education Program (NCEP) and International Diabetes Federation (IDF) criteria. Logistic regression was used to calculate the odds ratio (OR) per SD increase in adipose tissue. RESULTS: For total and all partial volumes, VAT was more strongly associated with metabolic syndrome than ASAT independent of metabolic syndrome criteria. The OR (per SD) for NCEP metabolic syndrome was higher for total VAT volume (OR = 7.26) and for the partial volumes at T12-L1 (7.46) and L1-L2 (8.77) than those at the L4-L5 level (3.94). The OR for metabolic syndrome ( approximately 2.6) was not substantially different among the ASAT measures. A similar pattern of association was observed using the IDF metabolic syndrome criteria. CONCLUSIONS: The measurement site for VAT, but not for ASAT, has a substantial influence on the magnitude of the association with both metabolic syndrome definitions. However, because VAT remained significantly associated with metabolic syndrome regardless of measurement site, the clinical interpretation was unaltered by measurement protocol or metabolic syndrome definition.

Abdominal Fat↗
PubMed2005

Cardiorespiratory fitness is an independent predictor of hypertension incidence among initially normotensive healthy women.

The authors examined the association between cardiorespiratory fitness and incident hypertension in women who were normotensive and free of cardiovascular disease at baseline in the Aerobics Center Longitudinal Study (Dallas, Texas), 1970-1998. A total of 4,884 women performed a maximal treadmill exercise test and completed a follow-up health survey. During an average follow-up of 5 years, 157 incident cases of self-reported, physician-diagnosed hypertension were identified from the health surveys. The cumulative incidence of hypertension was 3.2%. Compared with the rates of low-fit women, crude hypertension rates were 60% and 79% lower among women in the moderate and high fitness categories, respectively (p < 0.001). After adjustment for several potential confounders, the odds ratios for hypertension were 1.0, 0.61 (95% confidence interval (CI): 0.30, 1.21), and 0.35 (95% CI: 0.17, 0.73) in low-, moderately, and highly fit women, respectively (p(trend) < 0.01). Each 1-metabolic equivalent increment in treadmill performance was, on average, associated with a 19% (95% CI: 10, 27; p < 0.001) lower odds of incident hypertension. The pattern and strength of association between fitness and hypertension persisted in analyses stratified on body mass index, age, and the presence of prehypertension at baseline. An active lifestyle should be promoted for the primary prevention of hypertension in women.

Adult↗
PubMed2005

Cardiorespiratory fitness and body mass index as predictors of cardiovascular disease mortality among men with diabetes.

BACKGROUND: Questions remain as to whether higher levels of cardiorespiratory fitness, a measure of regular physical activity, are associated with lower risk of cardiovascular disease (CVD) mortality in overweight and obese individuals with diabetes. Our objective was to quantify the independent and joint relations of cardiorespiratory fitness (hereafter, fitness) and body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters) with CVD mortality in men with diabetes. METHODS: This study was conducted using prospective observational data from the Aerobics Center Longitudinal Study. Study participants comprised 2316 men with no history of stroke or myocardial infarction and who were diagnosed as having diabetes (mean [SD] age, 50 [10] years); had a medical examination, including a maximal exercise test during 1970 to 1997 with mortality surveillance to December 31, 1998; and had a BMI of 18.5 or greater and less than 35.0. The main outcome measure was CVD mortality across levels of fitness with stratification by BMI. RESULTS: We identified 179 CVD deaths during a mean (SD) follow-up of 15.9 (7.9) years and 36,710 man-years of exposure. In a model containing age, examination year, fasting glucose level, systolic blood pressure, parental history of premature CVD, total cholesterol level, cigarette smoking, abnormal resting, and exercise electrocardiograms, a significantly higher adjusted risk of mortality was observed in men with a low fitness level who were normal weight (hazard ratio, 2.7 [95% confidence interval, 1.3-5.7]), overweight (hazard ratio, 2.7 [95% confidence interval, 1.4-5.1]), and class 1 obese (hazard ratio, 2.8 [95% confidence interval, 1.4-5.1]) compared with normal weight men with a high fitness level. CONCLUSION: In this cohort of men with diabetes, low fitness level was associated with increased risk of CVD mortality within normal weight, overweight, and class 1 obese weight categories.

Body Mass Index↗
PubMed2005

Revised Adult Treatment Panel III guidelines and cardiovascular disease mortality in men attending a preventive medical clinic.

BACKGROUND: National Cholesterol Education Program Adult Treatment Panel III guidelines recommend therapeutic lifestyle changes (TLC) and drug therapy to reduce cardiovascular disease (CVD) risk. These guidelines have been revised recently (ATP III-R); however, the risk of CVD mortality within each intervention window and the effects of cardiorespiratory fitness (CRF) and metabolic syndrome on CVD mortality within the framework of the guidelines are unknown. METHODS AND RESULTS: Risk factor and CRF data from 19,125 men (aged 20 to 79 years) who attended a preventive medical clinic between 1979 and 1995 were used. Mortality follow-up was completed until December 31, 1996. Participants were assigned to ATP III-R groups (LDL-C goal, TLC initiation, and drug consideration), and risk of CVD mortality was assessed by Cox proportional hazards regression. There were 179 CVD deaths over an average 10.2 years of follow-up. Compared with the LDL-C goal group, men in the TLC initiation and drug consideration groups had an elevated risk of CVD mortality (TLC initiation: HR=2.65, 95% CI 1.67 to 4.19; drug consideration: HR=6.44, 95% CI 4.49 to 9.25). Compared with LDL-C goal/fit, CVD mortality risk was higher in the LDL-C goal/unfit (4.8, 2.5 to 9.1), TLC initiation/fit (3.0, 1.7 to 5.3), TLC initiation/unfit (7.5, 3.7 to 15.2), drug consideration/fit (7.2, 4.6 to 11.4), and drug consideration/unfit (14.9, 9.1 to 24.4) groups. A similar gradient was observed for metabolic syndrome across intervention windows. CONCLUSIONS: Men eligible for TLC or drug consideration under ATP III-R were at elevated risk of CVD mortality compared with men who met the LDL-C goal. Furthermore, men who were physically fit or who did not have the metabolic syndrome had a lower risk of CVD mortality.

Adult↗
PubMed2005

Coronary artery calcium score and coronary heart disease events in a large cohort of asymptomatic men and women.

Coronary artery calcium (CAC), a measure of subclinical coronary heart disease (CHD), may be useful in identifying asymptomatic persons at risk of CHD events. The current study included 10,746 adults who were 22-96 years of age, were free of known CHD, and had their CAC quantified by electron-beam tomography at baseline as part of a preventive medical examination at the Cooper Clinic (Dallas, Texas) during 1995-2000. During a mean follow-up of 3.5 years, 81 hard events (CHD death, nonfatal myocardial infarction) and 287 total events (hard events plus coronary revascularization) occurred. Age-adjusted rates (per 1,000 person-years) of hard events were computed according to four CAC categories: no detectable CAC and incremental sex-specific thirds of detectable CAC; these rates were, respectively, 0.4, 1.5, 4.8, and 8.7 (trend p<0.0001) for men and 0.7, 2.3, 3.1, and 6.3 (trend p=0.02) for women. CAC levels also were positively associated with rates of total CHD events for women and men (trend p<0.0001 each). The association between CAC and CHD events remained significant after adjustment for CHD risk factors. CAC was associated with CHD events in persons with no baseline CHD risk factors and in younger (aged <40 years) and older (aged >65 years) study participants. These findings show that CAC is associated with an increased risk of CHD events in asymptomatic women and men.

Adult↗