Randal J. Thomas

Accuracy of body mass index in diagnosing obesity in the adult general population.

Background:Body mass index (BMI) is the most widely used measure to diagnose obesity. However, the accuracy of BMI in detecting excess body adiposity in the adult general population is largely unknown.Methods:A cross-sectional design of 13u2009601 subjects (age 20–79.9 years; 49% men) from the Third National Health and Nutrition Examination Survey. Bioelectrical impedance analysis was used to estimate body fat percent (BF%). We assessed the diagnostic performance of BMI using the World Health Organization reference standard for obesity of BF%>25% in men and>35% in women. We tested the correlation between BMI and both BF% and lean mass by sex and age groups adjusted for race.Results:BMI-defined obesity (⩾30u2009kgu2009m−2) was present in 19.1% of men and 24.7% of women, while BF%-defined obesity was present in 43.9% of men and 52.3% of women. A BMI⩾30 had a high specificity (men=95%, 95% confidence interval (CI), 94–96 and women=99%, 95% CI, 98–100), but a poor sensitivity (men=36%, 95% CI, 35–37 and women=49%, 95% CI, 48–50) to detect BF%-defined obesity. The diagnostic performance of BMI diminished as age increased. In men, BMI had a better correlation with lean mass than with BF%, while in women BMI correlated better with BF% than with lean mass. However, in the intermediate range of BMI (25–29.9u2009kgu2009m−2), BMI failed to discriminate between BF% and lean mass in both sexes.Conclusions:The accuracy of BMI in diagnosing obesity is limited, particularly for individuals in the intermediate BMI ranges, in men and in the elderly. A BMI cutoff of⩾30u2009kgu2009m−2 has good specificity but misses more than half of people with excess fat. These results may help to explain the unexpected better survival in overweight/mild obese patients.

Central obesity and survival in subjects with coronary artery disease: A systematic review of the literature and collaborative analysis with individual subject data

OBJECTIVESnThe aim of this study was to examine the association of central (waist circumference [WC] and waist-hip ratio [WHR]) and total obesity (body mass index [BMI]) measures with mortality in coronary artery disease (CAD) patients.nnnBACKGROUNDnThe question of which measure of obesity better predicts survival in patients with CAD is controversial.nnnMETHODSnWe searched OVID/Medline, EMBASE, CENTRAL, and Web of Science from 1980 to 2008 and asked experts in the field for unpublished data meeting inclusion criteria, in which all subjects had: 1) CAD at baseline; 2) measures of WC or WHR; 3) mortality data; and 4) a minimum follow-up of 6 months.nnnRESULTSnFrom 2,188 studies found, 6 met inclusion criteria. We obtained individual subject data from 4, adding unpublished data from a cardiac rehabilitation cohort. A variable called central obesity was created on the basis of tertiles of WHR or WC. Cox-proportional hazards were adjusted for age, sex, and confounders. The final sample consisted of 15,923 subjects. There were 5,696 deaths after a median follow-up of 2.3 (interquartile range 0.5 to 7.4) years. Central obesity was associated with mortality (hazard ratio [HR]: 1.70, 95% confidence interval [CI]: 1.58 to 1.83), whereas BMI was inversely associated with mortality (HR: 0.64, 95% CI: 0.59 to 0.69). Central obesity was also associated with higher mortality in the subset of subjects with normal BMI (HR: 1.70, 95% CI: 1.52 to 1.89) and BMI ≥30 kg/m(2) (HR: 1.93, 95% CI: 1.61 to 2.32).nnnCONCLUSIONSnIn subjects with CAD, including those with normal and high BMI, central obesity but not BMI is directly associated with mortality.

Exercise Training and Cardiac Rehabilitation in Primary and Secondary Prevention of Coronary Heart Disease

Substantial data have established a sedentary lifestyle as a major modifiable risk factor for coronary heart disease (CHD). Increased levels of physical activity, exercise training, and overall cardiorespiratory fitness have provided protection in the primary and secondary prevention of CHD. This review surveys data from observational studies supporting the benefits of physical activity, exercise training, and overall cardiorespiratory fitness in primary prevention. Clearly, cardiac rehabilitation/secondary prevention (CRSP) programs have been greatly underused by patients with CHD. We review the benefits of CRSP programs on CHD risk factors, psychological factors, and overall CHD morbidity and mortality. These data support the routine referral of patients with CHD to CRSP programs. Patients should be vigorously encouraged to attend these programs.

Combined effect of cardiorespiratory fitness and adiposity on mortality in patients with coronary artery disease

BACKGROUNDnHigh cardiorespiratory fitness and body mass index (BMI) are associated with decreased mortality in patients with coronary artery disease. Our objective was to determine the joint impact of fitness and adiposity measures on all-cause mortality in this subgroup.nnnMETHODSnCoronary artery disease patients (n = 855) enrolled in the Mayo Clinic cardiac rehabilitation program from 1993 to 2007 were included. Fitness levels were determined by cardiopulmonary exercise testing. Patients were divided into low and high fitness by sex-specific median values of peak oxygen consumption and total treadmill time. Adiposity was measured through BMI and waist-to-hip ratio (WHR).nnnRESULTSnThere were 159 deaths during 9.7 ± 3.6 years of mean follow-up. After adjusting for potential confounding factors, low fitness, shorter treadmill time, low BMI, and high WHR were significantly associated with increased mortality. Using low WHR-high fitness group as reference, significantly increased mortality was noted in low WHR-low fitness (hazard ratio 4.2, 95% CI, 1.8-9.8), centrally obese-high fitness (2.3, 1.0-5.4), and centrally obese-low fitness (6.1, 2.7-13.6) groups. Overweight-high fitness (2.2, 0.63-7.4), obese-high fitness (3.2, 0.88-11.4), and obese-low fitness (3.3, 0.96-11.4) subjects did not have a significantly different mortality as compared with the reference group of normal weight-high fitness subjects, whereas normal weight-low fitness (9.6, 2.9-31.8) and overweight-low fitness (6.8, 2.1-22.2) groups had significantly increased mortality.nnnCONCLUSIONSnLow fitness and central obesity were independently and cumulatively associated with increased mortality in coronary artery disease patients attending cardiac rehabilitation. The association of BMI with mortality is complex and altered by fitness levels.

A pilot study on the effects of exercise in patients with systemic lupus erythematosus

OBJECTIVEnA pilot study was designed to assess the efficacy and safety of different exercise therapies on patient-reported fatigue and functional status.nnnMETHODSnTen patients with systemic lupus erythematosus (SLE) were randomly placed in either an aerobic exercise group (group 1: n = 5) or a range of motion/muscle strengthening (ROM/MS) exercise group (group 2: n = 5). Outcome measures assessed at baseline and the end of the study were fatigue, functional status, disease activity, cardiovascular fitness, isometric strength, bone mineral density (BMD) of the lumbar spine and femoral neck, and parathyroid hormone and osteocalcin as representative bone biochemical markers for bone resorption and bone formation, respectively.nnnRESULTSnBoth aerobic and ROM/MS types of exercise were safe and did not worsen SLE disease activity. Patients in both exercise groups showed some improvement in fatigue, functional status, cardiovascular fitness, and muscle strength. Both groups showed increased bone turnover, but BMD was unchanged. Eighty percent of the patients met the compliance standard for the study.nnnCONCLUSIONSnThis pilot study shows the feasibility of exercise for SLE patients. The potential value of this approach shows promise in the routine management of these patients.

Positional Change in Blood Pressure and 8-Year Risk of Hypertension: The CARDIA Study

OBJECTIVEnTo assess the relationship between positional blood pressure change and 8-year incidence of hypertension in a biracial cohort of young adults.nnnSUBJECTS AND METHODSnParticipants from the Coronary Artery Risk Development in Young Adults (CARDIA) study with complete data from year 2 (1987-1988), year 5 (1990-1991), year 7 (1992-1993), and year 10 (1995-1996) examinations were included (N = 2781). Participants were classified into 3 groups based on their year 2 systolic blood pressure response to standing: drop, a decrease in systolic blood pressure of more than 5 mm Hg; same, a change of between -5 and +5 mm Hg; and rise, more than 5-mm Hg increase.nnnRESULTSnThe number of participants in each group was as follows: drop, 741; same, 1590; and rise, 450. The 8-year incidence of hypertension was 8.4% in the drop group, 6.8% in the same group, and 12.4% in the rise group (P < .001). Adjusted odds ratios for developing hypertension during the follow-up period in the rise group vs the same group were as follows: in black men, 2.85 (95% confidence interval [CI], 1.43-5.69), in black women, 2.47 (95% CI, 1.19-5.11), in white men, 2.17 (95% CI, 1.00-4.73), and in white women, 4.74 (95% CI, 1.11-20.30).nnnCONCLUSIONSnA greater than 5-mm Hg increase in blood pressure on standing identified a group of young adults at increased risk of developing hypertension within 8 years. These findings support a physiologic link between sympathetic nervous system reactivity and risk of hypertension in young adults.

The Comparative Effectiveness of Heart Disease Prevention and Treatment Strategies

BACKGROUNDnPolicymakers must be able to calculate the comparative effectiveness of interventions to control heart disease if they are to optimize the population impact of programmatic initiatives.nnnMETHODSnA model was created to calculate the number of deaths that would be prevented or postponed if perfect care for heart disease prevention and treatment were achieved--that is, the elimination of risk factors and the prescription of all effective medications before and between acute events, and the delivery of all effective therapies to individuals suffering an acute heart disease event. The impact of perfect care was calculated for a hypothetic population aged 30-84 years with risk-factor levels, event rates, current patterns of behavior, levels of treatment, and mortality rates resembling those of the U.S. The analysis was performed in 2007 and 2008.nnnRESULTSnIn this population, 44% of all deaths were due to heart disease. Perfect care before the first heart disease event would prevent or postpone 33% of all deaths. Perfect care between acute events would prevent or postpone 23% of all deaths. Perfect care during acute events would prevent or postpone 8% of all deaths.nnnCONCLUSIONSnThis direct comparison of heart disease prevention and treatment strategies indicates that nearly 90% of the impact from perfect care for heart disease would accrue from interventions before and between acute events. The impact of risk-factor interventions before or between events is amplified by the fact that these interventions also reduce the risk of death from other chronic diseases.

Recognition, diagnosis and management of obesity after myocardial infarction

OBJECTIVE:We investigated the documentation of obesity as a medical problem, and subsequent management recommendations, in patients after myocardial infarction (MI).DESIGN:We performed a cross-sectional analysis of a randomly selected sample of 627 patients discharged after an MI, from five US teaching hospitals between 1/1/01 and 12/31/02. Information was extracted from clinical notes using standardized definitions.RESULTS:Mean body mass index (BMI) was 31±13 kg/m2, which was documented in only 14% of patients and had to be calculated post hoc in the rest. Waist circumference and waist/hip ratio were not documented at all; 83% of patients were overweight, 55% obese, and 8% morbidly obese. In only 20% of patients with BMI≥30 kg/m2 was the diagnosis of obesity documented either as a current medical problem, as part of past medical history or as a final diagnosis. A dietary counseling was carried out in 61% of patients with BMI≥25 kg/m2 and in 61% of patients with BMI<25 kg/m2, P=0.96. Weight loss was described as part of the goals/plan at discharge in 7% of overweight and 9% of obese patients. There was no change in either the level of recognition of obesity (22 vs 19%, P=0.3) or in the proportion of obese patients for whom weight loss was described as part of the goals/plan at discharge (8 vs 10%, P=0.7) before (n=301) compared to after (n=326) the Call to Action in Obesity by the Surgeon General in December 2001.CONCLUSION:Obesity is underecognized, underdiagnosed and undertreated in persons with acute MI.

Screening for obstructive sleep apnea in early outpatient cardiac rehabilitation: Feasibility and results

BACKGROUNDnObstructive sleep apnea (OSA) has been recognized as a risk factor for cardiovascular disease and mortality. The aim of this study was to determine the feasibility and efficacy of implementing a screening program for OSA in early outpatient cardiac rehabilitation (CR) and to estimate the risk for OSA in this population.nnnMETHODSnFrom 535 consecutive patients enrolled in early outpatient CR we screened 383 (72%) patients and classified them as low- vs. high-risk for OSA using the Berlin questionnaire. Those considered at high-risk for OSA were referred for further evaluation. We assessed the yield and feasibility of the screening program, patient compliance with referral, and the percentage of patients diagnosed with OSA after polysomnography.nnnRESULTSnMean age was 63 ± 12 years, 70% were men, 20% had diabetes, 65% had hypertension, and 58% had experienced a recent myocardial infarction. Two hundred and one patients (52%) had a high risk for OSA based on the questionnaire. Of the 169 who completed the CR program, only 111 (78%) were referred for further evaluation (Fig. 1). Of the 74 patients who completed their OSA work-up, 39 were found to have OSA with an apnea-hypopnea index of ≥ 5 events/h.nnnCONCLUSIONSnImplementation of a simple screening program for OSA in early outpatient CR is feasible with minimal incremental resources. A significant percentage of patients at high-risk decline further evaluation, suggesting that their perceived risk for OSA and its consequences may be low.

Exercise DVD improves exercise expectations in cardiovascular outpatients

OBJECTIVEnTo assess impact of exercise education intervention on exercise frequency and attitudes.nnnMETHODSnCardiovascular outpatients (N=509) were randomized to receive an education DVD or standard care. Outcome measures (baseline and 6 weeks) assessed exercise frequency and cognitive variables.nnnRESULTSnThere was no difference between groups on exercise frequency change from baseline, but DVD group reported greater exercise outcome expectations than control group (P=0.01). There was a greater increase in relapse-prevention behavior in the DVD group, compared to control, for those with low relapse-prevention behavior at baseline (P=0.02).nnnCONCLUSIONnA minimal intervention improves outcome expectations for exercise.