Francisco Lopez-Jimenez

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 13 601 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 (⩾30 kg m−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 (25–29.9 kg m−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⩾30 kg m−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.

Assessing Adiposity: A Scientific Statement From the American Heart Association

The prevalence of obesity in the United States and the world has risen to epidemic/pandemic proportions. This increase has occurred despite great efforts by healthcare providers and consumers alike to improve the health-related behaviors of the population and a tremendous push from the scientific community to better understand the pathophysiology of obesity. This epidemic is all the more concerning given the clear association between excess adiposity and adverse health consequences such as cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM). The risks associated with overweight/obesity are primarily related to the deposition of adipose tissue, which leads to excess adiposity or body fatness. Furthermore, weight loss, specifically loss of body fat, is associated with improvement in obesity-related comorbidities. Before weight loss interventions can be recommended, however, patients must be assessed for their adiposity-related risk. Unfortunately, healthcare providers and systems have not done a good job of assessing for excess adiposity even in its simplest form, such as measuring body mass index (BMI). It is for these reasons that we must emphasize the importance of assessing adiposity in clinical practices. Although it can be argued that the entire population should be targeted as an important public health issue with a goal of prevention of weight gain and obesity, there are currently so many “at risk” individuals that simple strategies to identify and treat those individuals are necessary. We must identify those individuals at highest risk of comorbidities in order to identify those who might benefit the most from aggressive weight management. This scientific statement will first briefly review the epidemiology of obesity and its related comorbidities, supporting the need for improved assessment of adiposity in daily clinical practice. This will be followed by a discussion of some of the challenges and issues associated with assessing adiposity and then by a review …

Diagnostic performance of body mass index to identify obesity as defined by body adiposity: a systematic review and meta-analysis

Objective:We performed a systematic review and meta-analysis of studies that assessed the performance of body mass index (BMI) to detect body adiposity.Design:Data sources were MEDLINE, EMBASE, Cochrane, Database of Systematic Reviews, Cochrane CENTRAL, Web of Science, and SCOPUS. To be included, studies must have assessed the performance of BMI to measure body adiposity, provided standard values of diagnostic performance, and used a body composition technique as the reference standard for body fat percent (BF%) measurement. We obtained pooled summary statistics for sensitivity, specificity, positive and negative likelihood ratios (LRs), and diagnostic odds ratio (DOR). The inconsistency statistic (I2) assessed potential heterogeneity.Results:The search strategy yielded 3341 potentially relevant abstracts, and 25 articles met our predefined inclusion criteria. These studies evaluated 32 different samples totaling 31 968 patients. Commonly used BMI cutoffs to diagnose obesity showed a pooled sensitivity to detect high adiposity of 0.50 (95% confidence interval (CI): 0.43–0.57) and a pooled specificity of 0.90 (CI: 0.86–0.94). Positive LR was 5.88 (CI: 4.24–8.15), I 2=97.8%; the negative LR was 0.43 (CI: 0.37–0.50), I 2=98.5%; and the DOR was 17.91 (CI: 12.56–25.53), I 2=91.7%. Analysis of studies that used BMI cutoffs ⩾30 had a pooled sensitivity of 0.42 (CI: 0.31–0.43) and a pooled specificity of 0.97 (CI: 0.96–0.97). Cutoff values and regional origin of the studies can only partially explain the heterogeneity seen in pooled DOR estimates.Conclusion:Commonly used BMI cutoff values to diagnose obesity have high specificity, but low sensitivity to identify adiposity, as they fail to identify half of the people with excess BF%.

Normal weight obesity: a risk factor for cardiometabolic dysregulation and cardiovascular mortality

AIMS We hypothesized that subjects with a normal body mass index (BMI), but high body fat (BF) content [normal weight obesity (NWO)], have a higher prevalence of cardiometabolic dysregulation and are at higher risk for cardiovascular (CV) mortality. METHODS AND RESULTS We analysed 6171 subjects >20 years of age from the Third National Health and Nutrition Examination Survey (NHANES III) and the NHANES III mortality study, whose BMI was within the normal range (18.5-24.9 kg/m(2)), and who underwent a complete evaluation that included body composition assessment, blood measurements, and assessment of CV risk factors. Survival information was available for >99% of the subjects after a median follow-up of 8.8 years. We divided our sample using sex-specific tertiles of BF%. The highest tertile of BF (>23.1% in men and >33.3% in women) was labelled as NWO. When compared with the low BF group, the prevalence of metabolic syndrome in subjects with NWO was four-fold higher (16.6 vs. 4.8%, P < 0.0001). Subjects with NWO also had higher prevalence of dyslipidaemia, hypertension (men), and CV disease (women). After adjustment, women with NWO showed a significant 2.2-fold increased risk for CV mortality (HR = 2.2; 95% CI, 1.03-4.67) in comparison to the low BF group. CONCLUSION Normal weight obesity, defined as the combination of normal BMI and high BF content, is associated with a high prevalence of cardiometabolic dysregulation, metabolic syndrome, and CV risk factors. In women, NWO is independently associated with increased risk for CV mortality.

Interactions Between Obesity and Obstructive Sleep Apnea: Implications for Treatment

Obstructive sleep apnea (OSA) adversely affects multiple organs and systems, with particular relevance to cardiovascular disease. Several conditions associated with OSA, such as high BP, insulin resistance, systemic inflammation, visceral fat deposition, and dyslipidemia, are also present in other conditions closely related to OSA, such as obesity and reduced sleep duration. Weight loss has been accompanied by improvement in characteristics related not only to obesity but to OSA as well, suggesting that weight loss might be a cornerstone of the treatment of both conditions. This review seeks to explore recent developments in understanding the interactions between body weight and OSA. Weight loss helps reduce OSA severity and attenuates the cardiometabolic abnormalities common to both diseases. Nevertheless, weight loss has been hard to achieve and maintain using conservative strategies. Since bariatric surgery has emerged as an alternative treatment of severe or complicated obesity, impressive results have often been seen with respect to sleep apnea severity and cardiometabolic disturbances. However, OSA is a complex condition, and treatment cannot be limited to any single symptom or feature of the disease. Rather, a multidisciplinary and integrated strategy is required to achieve effective and long-lasting therapeutic success.

Prognostic value of cardiac troponin T after noncardiac surgery: 6-Month follow-up data

OBJECTIVES We sought to evaluate the prognostic significance of cardiac troponin T (TnT) serum levels after noncardiac surgery. BACKGROUND Cardiac TnT has been found to be marker for myocardial injury, but elevations of TnT are common in patients undergoing noncardiac surgery without clinical evidence of severe ischemia. METHODS We studied 772 patients who underwent major noncardiac procedures and did not have major cardiovascular complications during their inpatient course. Total serum creatine kinase (CK) and cardiac TnT were measured according to a protocol that included sampling in the recovery room and during the next 2 days. A 6-month follow-up interview was performed for 722 (94%) of the patients. RESULTS Elevated cardiac TnT and CK-MB results were detected for 92 (12%) and 211 (27%) patients, respectively. During the follow-up period, there were 19 (2.5%) major cardiac complications, including 14 cardiac deaths, 3 nonfatal myocardial infarctions and 2 admissions for unstable angina. Compared with patients with cardiac TnT values < 0.1 ng/ml, patients with elevated TnT had a relative risk for cardiac events of 5.4 (95% confidence interval: 2.2 to 13, p = 0.001), whereas CK-MB was not correlated with postdischarge cardiac events. In multivariate logistic regression analysis adjusting for preoperative clinical and CK-MB data, a cardiac TnT value > 0.1 ng/ml was in independent correlate of cardiac events (adjusted odds ratio 4.6, p < 0.05). This correlation was a function of the relation of elevated TnT levels with postoperative in-hospital congestive heart failure and new sustained arrhythmias, suggesting that elevated postoperative TnT levels detected myocardial ischemia during these clinical events. CONCLUSIONS We conclude that an abnormal TnT level in patients undergoing noncardiac surgery may be a useful marker of ischemic disease and a predictor of 6-month prognosis.

Association Between Lipoprotein-Associated Phospholipase A2 and Cardiovascular Disease: A Systematic Review

OBJECTIVE To estimate the association between plasma lipoprotein-associated phospholipase A2 (Lp-PLA2) levels and cardiovascular disease (CVD). METHODS We searched MEDLINE (January 1, 1985, through September 30, 2006), the Cochrane library (from inception through 2006), conference proceedings, and reference sections of obtained articles and contacted experts for unpublished studies. Eligible studies were cohorts with 1 year or more of follow-up or case-control designs that provided risk estimates for CVD according to blood levels of Lp-PLA2 that were unadjusted or adjusted for conventional CVD risk factors. We used random-effects meta-analysis to estimate the association between Lp-PLA2 and CVD risk and conducted preplanned subgroup analyses to identify risk-subgroup interactions that could explain between-study differences. RESULTS We found 14 eligible studies (N = 20,549 patients) that reported either Lp-PLA2 plasma activity (n = 5) or an immunoassay that measured the plasma concentration (n = 9). The meta-analytic estimate from the unadjusted odds ratio for the association between elevated Lp-PLA2 levels and CVD risk was 1.51 (95% confidence interval, 1.30-1.75) and from the odds ratio adjusted for conventional CVD risk factors was 1.60 (95% confidence interval, 1.36-1.89). Differences in study methods explained differences in results across studies. CONCLUSIONS Lipoprotein-associated phospholipase A2 is significantly associated with CVD. The risk estimate appears to be relatively unaffected by adjustment for conventional CVD risk factors. Measurement of Lp-PLA2 may be useful in CVD risk stratification. In addition, Lp-PLA2 may represent a potential therapeutic target for CVD risk reduction.

Day-Night Variation of Acute Myocardial Infarction in Obstructive Sleep Apnea

OBJECTIVES This study sought to evaluate the day-night variation of acute myocardial infarction (MI) in patients with obstructive sleep apnea (OSA). BACKGROUND Obstructive sleep apnea has a high prevalence and is characterized by acute nocturnal hemodynamic and neurohormonal abnormalities that may increase the risk of MI during the night. METHODS We prospectively studied 92 patients with MI for which the time of onset of chest pain was clearly identified. The presence of OSA was determined by overnight polysomnography. RESULTS For patients with and without OSA, we compared the frequency of MI during different intervals of the day based on the onset time of chest pain. The groups had similar prevalence of comorbidities. Myocardial infarction occurred between 12 am and 6 am in 32% of OSA patients and 7% of non-OSA patients (p = 0.01). The odds of having OSA in those patients whose MI occurred between 12 am and 6 am was 6-fold higher than in the remaining 18 h of the day (95% confidence interval: 1.3 to 27.3, p = 0.01). Of all patients having an MI between 12 am and 6 am, 91% had OSA. CONCLUSIONS The diurnal variation in the onset of MI in OSA patients is strikingly different from the diurnal variation in non-OSA patients. Patients with nocturnal onset of MI have a high likelihood of having OSA. These findings suggest that OSA may be a trigger for MI. Patients having nocturnal onset of MI should be evaluated for OSA, and future research should address the effects of OSA therapy for prevention of nocturnal cardiac events.

Sarcopenia, sarcopenic obesity and mortality in older adults: results from the National Health and Nutrition Examination Survey III

Background:Sarcopenia is defined as the loss of skeletal muscle mass and quality, which accelerates with aging and is associated with functional decline. Rising obesity prevalence has led to a high-risk group with both disorders. We assessed mortality risk associated with sarcopenia and sarcopenic obesity in elders.Methods:A subsample of 4652 subjects ⩾60 years of age was identified from the National Health and Nutrition Examination Survey III (1988–1994), a cross-sectional survey of non-institutionalized adults. National Death Index data were linked to this data set. Sarcopenia was defined using a bioelectrical impedance formula validated using magnetic resonance imaging-measured skeletal mass by Janssen et al. Cutoffs for total skeletal muscle mass adjusted for height2 were sex-specific (men: ⩽5.75 kg/m2; females ⩽10.75 kg/m2). Obesity was based on % body fat (males: ⩾27%, females: ⩾38%). Modeling assessed mortality adjusting for age, sex, ethnicity (model 1), comorbidities (hypertension, diabetes, congestive heart failure, osteoporosis, cancer, coronary artery disease and arthritis), smoking, physical activity, self-reported health (model 2) and mobility limitations (model 3).Results:Mean age was 70.6±0.2 years and 57.2% were female. Median follow-up was 14.3 years (interquartile range: 12.5–16.1). Overall prevalence of sarcopenia was 35.4% in women and 75.5% in men, which increased with age. Prevalence of obesity was 60.8% in women and 54.4% in men. Sarcopenic obesity prevalence was 18.1% in women and 42.9% in men. There were 2782 (61.7%) deaths, of which 39.0% were cardiovascular. Women with sarcopenia and sarcopenic obesity had a higher mortality risk than those without sarcopenia or obesity after adjustment (model 2, hazard ratio (HR): 1.35 (1.05–1.74) and 1.29 (1.03–1.60)). After adjusting for mobility limitations (model 3), sarcopenia alone (HR: 1.32 ((1.04–1.69) but not sarcopenia with obesity (HR: 1.25 (0.99–1.58)) was associated with mortality. For men, the risk of death with sarcopenia and sarcopenic obesity was nonsignificant in both model-2 (HR: 0.98 (0.77–1.25), and HR: 0.99 (0.79–1.23)) and model 3 (HR: 0.98 (0.77–1.24) and HR: 0.98 (0.79–1.22)).Conclusions:Older women with sarcopenia have an increased all-cause mortality risk independent of obesity.

Independent Association Between Obstructive Sleep Apnea and Subclinical Coronary Artery Disease

BACKGROUND Obstructive sleep apnea (OSA) is associated with coronary risk factors, but it is unknown if OSA is associated with development of coronary disease. We evaluated the association between OSA and the presence of subclinical coronary disease assessed by coronary artery calcification (CAC). METHODS Consecutive patients with no history of coronary disease who underwent electron-beam CT within 3 years of polysomnography between March 1991 and December 2003 were included. OSA was defined by an apnea-hypopnea index (AHI) > or = 5 events per hour, and patients were grouped by quartiles of AHI severity. Logistic regression modeled the association between OSA severity and presence of CAC. RESULTS There were 202 patients (70% male; median age, 50 years; mean body mass index, 32 kg/m(2); 8% diabetic; 9% current smokers; 60% hypercholesterolemic; and 47% hypertensive). OSA was present in 76%. CAC was present in 67% of OSA patients and 31% of non-OSA patients (p < 0.001). Median CAC scores (Agatston units) were 9 in OSA patients and 0 in non-OSA patients (p < 0.001). Median CAC score was higher as OSA severity increased (p for trend by AHI quartile < 0.001). With multivariate adjustment, the odds ratio for CAC increased with OSA severity. Using the first AHI quartile as reference, the adjusted odds ratios for the second, third, and fourth quartiles were 2.1 (p = 0.12), 2.4 (p = 0.06), and 3.3 (p = 0.03), respectively. CONCLUSIONS In patients without clinical coronary disease, the presence and severity of OSA is independently associated with the presence and extent of CAC. OSA identifies patients at risk for coronary disease and may represent a highly prevalent modifiable risk factor.