Association Between Body Mass Index, Obesity, and Clinical Outcomes Following Coronary Artery Bypass Grafting in Brazil: An Analysis of One Year of Follow-up of BYPASS Registry Patients

OBJECTIVE

To investigate the association between body mass index (BMI), obesity, clinical outcomes, and mortality following coronary artery bypass grafting (CABG) in Brazil using a large sample with one year of follow-up from the Brazilian Registry of Cardiovascular Surgeries in Adults (or BYPASS) Registry database.

METHODS

A multicenter cohort-study enrolled 2,589 patients submitted to isolated CABG and divided them into normal weight (BMI 20.0-24.9 kg/m2), overweight (BMI 25.0-29.9 kg/m2), and obesity (BMI > 30.0 kg/m2) groups. Inpatient postoperative outcomes included the most frequently described complications and events. Collected post-discharge outcomes included rehospitalization and mortality rates within 30 days, six months, and one year of follow-up.

RESULTS

Sternal wound infections (SWI) rate was higher in obese compared to normal-weight patients (relative risk [RR]=5.89, 95% confidence interval [CI]=2.37-17.82; P=0.001). Rehospitalization rates in six months after discharge were higher in obesity and overweight groups than in normal weight group (χ=6.03, P=0.049); obese patients presented a 2.2-fold increase in the risk for rehospitalization within six months compared to normal-weight patients (RR=2.16, 95% CI=1.17-4.09; P=0.045). Postoperative complications and mortality rates did not differ among groups during time periods.

CONCLUSION

Obesity increased the risk for SWI, leading to higher rehospitalization rates and need for surgical interventions within six months following CABG. Age, female sex, and diabetes were associated with a higher risk of mortality. The obesity paradox remains controversial since BMI may not be sufficient to assess postoperative risk in light of more complex and dynamic evaluations of body composition and physical fitness.

The impact of obesity on ventilator-associated pneumonia, a US nationwide study

BACKGROUND

Ventilator-associated pneumonia (VAP) is one of the leading causes of mortality in patients with critical care illness. Since obesity is highly prevalent, we wanted to study its impact on the outcomes of patients who develop VAP.

METHODS

Using the National Inpatient Sample (NIS) database from 2017 to 2020, we conducted a retrospective study of adult patients with a principal diagnosis of VAP with a secondary diagnosis with or without obesity according to 10th revision of the International Statistical Classification of Diseases (ICD-10) codes. Several demographics, including age, race, and gender, were analyzed. The primary endpoint was mortality, while the secondary endpoints included tracheostomy, length of stay in days, and patient charge in dollars. Multivariate logistic regression model analysis was used to adjust for confounders, with a p-value less than 0.05 considered statistically significant.

RESULTS

The study included 3832 patients with VAP, 395 of whom had obesity. The mean age in both groups was around 58 years, and 68% of the group with obesity were females compared to 40% in females in the group without obesity. Statistically significant comorbidities in the obesity group included a Charlson Comorbidity Index score of three and above, diabetes mellitus, hypertension, chronic kidney disease, and sleep apnea. Rates and odds of mortality were not significantly higher in the collective obesity group 39 (10%) vs. 336 (8.5%), p-value 0.62, adjusted odds ratio 1.2, p-value 0.61). The rates and odds of tracheostomy were higher in the obesity group but not statistically significant. Obese patients were also found to have a longer hospitalization. Upon subanalysis of the data, no evidence of racial disparities was found in the care of VAP for both the obese and control groups.

CONCLUSIONS

Obesity was not found to be an independent risk factor for worse outcomes in patients who develop VAP in the intensive care unit.

Body Mass Index and Clinical and Health Status Outcomes in Chronic Coronary Disease and Advanced Kidney Disease in the ISCHEMIA-CKD Trial

OBJECTIVE

This study aimed to assess whether an obesity paradox (lower event rates with higher body mass index [BMI]) exists in participants with advanced chronic kidney disease (CKD) and chronic coronary disease in the International Study of Comparative Health Effectiveness of Medical and Invasive Approaches (ISCHEMIA)-CKD, and whether BMI modified the effect of initial treatment strategy.

METHODS

Baseline BMI was analyzed as both a continuous and categorical variable (< 25, ≥ 25 to < 30, ≥ 30 kg/m2). Associations between BMI and the primary outcome of all-cause death or myocardial infarction (D/MI), and all-cause death, cardiovascular death, and MI individually were estimated. Associations with health status were also evaluated using the Seattle Angina Questionnaire-7, the Rose Dyspnea Scale, and the EuroQol-5D Visual Analog Scale.

RESULTS

Body mass index ≥ 30 kg/m2 vs < 25 kg/m2 demonstrated increased risk for MI (hazard ratio [HR] [95% confidence interval] = 1.81 [1.12-2.92]) and for D/MI (HR 1.45 [1.06-1.96]) with a HR for MI of 1.22 (1.05-1.40) per 5 kg/m2 increase in BMI in unadjusted analysis. In multivariate analyses, a BMI ≥ 30 kg/m2 was marginally associated with D/MI (HR 1.43 [1.00-2.04]) and greater dyspnea throughout follow-up (P < .05 at all time points). Heterogeneity of treatment effect between baseline BMI was not evident for any outcome.

CONCLUSIONS

In the ISCHEMIA-CKD trial, an obesity paradox was not detected. Higher BMI was associated with worse dyspnea, and a trend toward increased D/MI and MI risk. Larger studies to validate these findings are warranted.

Abdominal obesity and hydration status as protective factors against mortality in older adults: A prospective study

OBJECTIVES

The aim of this study was to assess the association between different anthropometric and body composition techniques for defining obesity status and to investigate their clinical implications in older hospitalized patients, both during their hospitalization and after discharge.

METHODS

This prospective study included patients ≥60 y of age. They were followed for 18 mo to assess mortality and hospital length of stay. Anthropometric measurements and body composition were evaluated, including body mass index (BMI), waist circumference, waist-to-height ratio, body fat percentage, total body water percentage, and muscle mass. These measurements are associated with prognosis and survival.

RESULTS

A higher BMI, excessive body fat, higher total body water percentage, and abdominal obesity were associated with a lower risk for death (P < 0.05). Higher hydration levels were identified as an independent protective factor against mortality. Obesity, defined by body fat percentage, was associated with a shorter hospital stay (P < 0.05).

CONCLUSION

The present study adds to the growing body of evidence supporting the existence of the obesity paradox in hospitalized older patients. Additionally, our novel finding reveals that higher levels of total body water percentage are associated with decreased odds of mortality. The study emphasizes the importance of considering other anthropometric measurements and body composition in addition to BMI, considering its limitations. These findings have important implications for health care providers when recommending changes in nutritional status for the older adult population.

Longitudinal Assessment of Body Composition and Its Association With Survival Among Participants of the ACTIVE/ADIPOSE Study

OBJECTIVES

The importance of muscle wasting as a predictor of mortality in the hemodialysis population is not clear. Lack of association of muscle mass with survival in some studies could be related to reliance on single measures or to incorporation of excess extracellular water (ECW) into estimates of muscle mass. We examined changes in body composition over a 2-year period and the association of body composition with survival.

DESIGN AND METHODS

We analyzed data from 325 adults receiving hemodialysis in the Bay Area. We estimated ECW, intracellular water (ICW), and fat mass by whole-body bioimpedance spectroscopy (BIS) at 0, 12, and 24 months from enrollment. We used linear mixed modeling to examine changes in body mass index and BIS-derived estimates of body composition and Cox modeling with BIS-derived estimates as time-varying independent variables to examine associations between body composition and survival in multivariable analyses.

RESULTS

Body mass index declined over time. Considering individual components of body composition, ICW declined (-0.09 kg/m² per year, 95% confidence interval -0.14 to -0.04), but fat mass and ECW did not change significantly. There were 120 deaths over a median of 5.2 years. The relationship between ICW and mortality was not linear such that the association was steeper at low values of ICW, whereas higher ICW was associated with better survival that was relatively stable above 9 kg/m2. Higher ECW was associated with higher mortality, and fat mass was not associated with survival. These associations were independent of markers of inflammation and nutritional status.

CONCLUSIONS

ICW declined over 2 years in this cohort, whereas fat mass and ECW remained relatively stable. Higher ICW was associated with better survival, but higher fat mass was not. Higher ECW was associated with worse survival. These results suggest that muscle mass may predict survival among patients on hemodialysis.

Influence of BMI on Short and Long-Term Outcomes in Patients With STEMI and LV Dysfunction

BACKGROUND

Recent studies suggest an obesity paradox in individuals with myocardial infarction with better outcomes in obese relative to normal weight patients. We assessed the influence of body mass index (BMI) on early and long-term outcomes in patients with ST elevation myocardial infarction (STEMI) and left ventricular (LV) dysfunction.

METHODS

Outcomes were assessed according to BMI status in 478 consecutive patients with STEMI and LV dysfunction (ejection fraction [EF]<40%) admitted to Westmead Hospital between 1 January 2004 and 16 April 2014. Normal weight, overweight and obesity were defined as BMI < 25, 25-29.9, and ≥30 kg/m2, respectively.

RESULTS

Obese patients were significantly younger (p = 0.01) and were more likely to have hypertension and diabetes (p = 0.04 and 0.001 respectively). In hospital outcomes and 30-day major adverse cardiac events (MACE) were similar in all three groups. There was no difference in recurrent myocardial infarction (MI) and target vessel revascularisation (TVR) during long-term follow-up (mean follow-up 809 days). Overall mortality following hospital discharge was significantly lower in overweight and obese patients. Adjusted hazard ratio for all-cause mortality in normal weight patients compared to overweight patients was 2.4 (95% C.I 1.1-5.3, p= -0.03). The adjusted hazard ratio for all-cause mortality in normal weight patients in comparison to obese patients was 2.7 (95% C.I, 1 -7.4, p = 0.05). Left ventricular ejection fraction (LVEF) and age were other predictors of all-cause mortality.

CONCLUSIONS

Normal weight, overweight and obese patients with STEMI and LV dysfunction had similar in hospital outcomes and 30-day outcomes. Long-term all-cause mortality was, however, higher in normal weight patients suggesting the presence of an obesity paradox in this cohort.

Obesity paradox, obesity orthodox, and the metabolic syndrome: An approach to unity

Obesity and the accompanying metabolic syndrome are strongly associated with heightened morbidity and mortality in older adults. In our review of more than 20 epidemiologic studies of major infectious diseases, including leaders such as tuberculosis, community-acquired pneumonia, and sepsis, obesity was associated with better outcomes. A cause-and-effect relationship between over-nutrition and survival with infection is suggested by results of two preliminary studies of infections in mice, where high fat feeding for 8-10 weeks provided much better outcomes. The better outcomes of infections with obesity are reminiscent of many recent studies of "sterile" non-infectious medical and surgical conditions where outcomes for obese patients are better than for their thinner counterparts --- and given the tag "obesity paradox". Turning to the history of medicine and biological evolution, we hypothesize that the metabolic syndrome has very ancient origins and is part of a lifelong metabolic program. While part of that program (the metabolic syndrome) promotes morbidity and mortality with aging, it helps infants and children as well as adults in their fight against infections and recovery from injuries, key roles in the hundreds of centuries before the public health advances of the 20th century. We conclude with speculation on how understanding the biological elements that protect obese patients with infections or injuries might be applied advantageously to thin patients with the same medical challenges.

Fitness Level is Associated with Sex-Specific Regional Fat Differences in Normal Weight Young Adults

OBJECTIVES

To characterize regional body composition and insulin sensitivity differences between young adults who were normal weight with either high or low fitness determined by VO₂ peak. We hypothesized that higher fitness levels would be associated with reduced visceral fat (VAT) and improved insulin sensitivity.

DESIGN

A cross-sectional comparison of normal weight males and females with high or low fitness matched on age and sex.

METHODS

A total of 38 (20M/18F) individuals were recruited for this study. Thirty-two young adults (18M/14F) were matched on age (mean 22.5 ± 3 yrs.) and BMI (22.4 ± 2.4 kg/m²) and sex and classified by high or low fitness based on VO₂ peak difference (≥ 8ml/kg/min). Total and regional body composition, including VAT, was measured by Dual Energy X-Ray Absorptiometry (DXA). Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp. An analysis of variance compared regional body composition and insulin sensitivity between high and low fitness young adults with a normal BMI.

RESULTS

Higher fitness was associated with significantly lower percent body fat, lower android fat mass and higher insulin sensitivity in males (-7.2%, P<0.001; -0.5kg, P=0.048; 5.6mg/kg (FFM)/min, p=0.002). In females, higher fitness was associated with significantly lower percent body fat, lower leg fat but no difference in insulin sensitivity (-6.7%, P=0.001; -2.7kg, P<0.001; 2.5 mg/kg(FFM)/min, P=0.40). No differences in VAT were observed between high and low fitness groups. Interestingly in females, there was no difference in total lean mass, trunk lean mass or leg lean mass (P=0.59, P=0.17, P=0.99).

CONCLUSION

Higher fitness does not influence VAT in normal weight individuals. Sex influenced regional fat and insulin sensitivity differences between high fitness and low fitness groups.