Association of Body Mass Index and Outcome in Acutely Ill Patients With Chronic Kidney Disease Requiring Intensive Care Therapy

Sex-Specific Obesity Paradox in Critically Ill Patients With Severe Acute Kidney Injury: A Retrospective Analysis

OBJECTIVES

Although obesity is typically correlated with adverse outcomes in various diseases, certain acute critical illnesses exhibit a phenomenon known as the obesity paradox. This study evaluated sex-specific differences in the prognostic implications of the body mass index (BMI) of patients with severe acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT).

DESIGN

A multicenter retrospective cohort study.

SETTING

Data from eight tertiary hospitals in Korea.

PATIENTS

A total of 3805 critically ill patients receiving CRRT. Patients were categorized into four BMI groups: underweight, normal weight, overweight, and obese.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

There were 2308 male and 1497 female patients. The 90-day mortality risk significantly differed among BMI groups in the overall patient population and the male subpopulation but not the female subpopulation. Following adjustment for confounding variables, the 90-day mortality risk was higher in the underweight group than in the obese group (hazard ratio [HR], 1.20; 95% CI, 1.05-1.36; p = 0.006). Among male patients, the 90-day mortality risk was higher in both the underweight and normal weight groups than in the obese group (underweight: HR, 1.30; 95% CI, 1.10-1.53; p = 0.002 and normal weight: HR, 1.18; 95% CI, 1.04-1.35; p = 0.010); however, no such association was observed among female patients. Subgroup analysis demonstrated the obesity paradox in male patients of old age, with septic AKI, or with low albumin levels.

CONCLUSIONS

There were sex differences in the association between BMI and mortality in critically ill patients with severe AKI. Although the precise distribution of fat mass and muscle mass was not identified, obese male patients had a more favorable prognosis, which was not evident among female patients. These findings highlight the importance of considering sex-specific factors in understanding the complex relationship between obesity and mortality in critically ill patients with AKI.

Obesity is associated with improved early survival but increased late mortality in surgical patients with Sepsis: A propensity matched analysis

BACKGROUND

While obesity is a risk factor for postoperative complications, its impact following sepsis is unclear. The primary objective of this study was to evaluate the association between obesity and mortality following admission to the surgical intensive care unit (SICU) with sepsis.

METHODS

We conducted a single center retrospective review of SICU patients grouped into obese (n = 766, body mass index ≥30 kg/m 2 ) and nonobese (n = 574; body mass index, 18-29.9 kg/m 2 ) cohorts. Applying 1:1 propensity matching for age, sex, comorbidities, sequential organ failure assessment, and transfer status, demographic data, comorbidities, and sepsis presentation were compared between groups. Primary outcomes included in-hospital and 90-day mortality, ICU length of stay, need for mechanical ventilation (IMV) and renal replacement therapy (RRT). p < 0.05 was considered significant.

RESULTS

Obesity associates with higher median ICU length of stay (8.2 vs. 5.6, p < 0.001), need for IMV (76% vs. 67%, p = 0.001), ventilator days (5 vs. 4, p < 0.004), and RRT (23% vs. 12%, p < 0.001). In-hospital (29% vs. 18%, p < 0.0001) and 90-day mortality (34% vs. 24%, p = 0.0006) was higher for obese compared with nonobese groups. Obesity independently predicted need for IMV (odds ratio [OR], 1.6; 95% confidence interval [CI], 1.2-2.1), RRT (OR, 2.2; 95% CI, 1.5-3.1), in-hospital (OR, 2.1; 95% CI, 1.5-2.8), and 90-day mortality (HR, 1.4; 95% CI, 1.1-1.8), after adjusting for sequential organ failure assessment, age, sex, and comorbidities. Comparative survival analyses demonstrate a paradoxical early survival benefit for obese patients followed by a rapid decline after 7 days (logrank p = 0.0009).

CONCLUSION

Obesity is an independent risk factor for 90-day mortality for surgical patients with sepsis, but its impact appeared later in hospitalization. Understanding differences in systemic responses between these cohorts may be important for optimizing critical care management.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level III.

Non-linear association between body weight and functional outcome after acute ischemic stroke

This study aimed to determine whether body weight is associated with functional outcome after acute ischemic stroke. We measured the body mass index (BMI) and assessed clinical outcomes in patients with acute ischemic stroke. The BMI was categorized into underweight (< 18.5 kg/m²), normal weight (18.5-22.9 kg/m²), overweight (23.0-24.9 kg/m²), and obesity (≥ 25.0 kg/m²). The association between BMI and a poor functional outcome (modified Rankin Scale [mRS] score: 3-6) was evaluated. We included 11,749 patients with acute ischemic stroke (70.3 ± 12.2 years, 36.1% women). The risk of a 3-month poor functional outcome was higher for underweight, lower for overweight, and did not change for obesity in reference to a normal weight even after adjusting for covariates by logistic regression analysis. Restricted cubic splines and SHapley Additive exPlanation values in eXtreme Gradient Boosting model also showed non-linear relationships. Associations between BMI and a poor functional outcome were maintained even after excluding death (mRS score: 3-5) or including mild disability (mRS score: 2-6) as the outcome. The associations were strong in older patients, non-diabetic patients, and patients with mild stroke. Body weight has a non-linear relationship with the risk of a poor functional outcome after acute ischemic stroke.

Obesity and Overweight Are Independently Associated with Greater Survival in Critically Ill Diabetic Patients: A Retrospective Cohort Study

BACKGROUND

The relationship between obesity and the outcomes of critically ill diabetic patients is not completely clear. We aimed to assess the effects of obesity and overweight on the outcomes among diabetic patients in the intensive care unit (ICU).

METHODS

Critically ill diabetic patients in the ICU were classified into three groups according to their body mass index. The primary outcomes were 30-day and 90-day mortality. ICU and hospital length of stay (LOS) and incidence and duration of mechanical ventilation were also assessed. Cox regression models were developed to evaluate the relationship between obesity and overweight and mortality.

RESULTS

A total of 6108 eligible patients were included. The 30-day and 90-day mortality in the normal weight group were approximately 1.8 times and 1.5 times higher than in the obesity group and overweight group, respectively (P < 0.001, respectively). Meanwhile, the ICU (median (IQ): 2.9 (1.7, 5.3) vs. 2.7 (1.6, 4.8) vs. 2.8 (1.8, 5.0)) and hospital (median (IQ): 8.3 (5.4, 14.0) vs. 7.9 (5.1, 13.0) vs. 8.3 (5.3, 13.6)) LOS in the obesity group and overweight group were not longer than in the normal weight group. Compared with normal weight patients, obese patients had significantly higher incidence of mechanical ventilation (58.8% vs. 64.7%, P < 0.001) but no longer ventilation duration (median (IQ): 19.3 (7.0, 73.1) vs. 19.0 (6.0, 93.7), P = 1). Multivariate Cox regression showed that obese and overweight patients had lower 30-day (HR (95% CI): 0.62 (0.51, 0.75); 0.76 (0.62, 0.92), respectively) and 90-day (HR (95% CI): 0.60 (0.51, 0.70); 0.79 (0.67, 0.93), respectively) mortality risks than normal weight patients.

CONCLUSIONS

Obesity and overweight were independently associated with greater survival in critically ill diabetic patients, without increasing the ICU and hospital LOS. Large multicenter prospective studies are needed to confirm our findings and the underlying mechanisms warrant further investigation.

Is There an Obesity Paradox in Critical Illness? Epidemiologic and Metabolic Considerations

PURPOSE OF REVIEW

Obesity represents a global epidemic with serious implications in public health due to its increasing prevalence and its known association with a high morbidity and mortality burden. However, a growing number of data support a survival benefit of obesity in critical illness. This review summarizes current evidence regarding the obesity paradox in critical illness, discusses methodological issues and metabolic implications, and presents potential pathophysiologic mechanisms.

RECENT FINDINGS

Data from meta-analyses and recent studies corroborate the obesity-related survival benefit in critically ill patients as well as in selected populations such as patients with sepsis and acute respiratory distress syndrome, but not trauma. However, this finding warrants a cautious interpretation due to certain methodological limitations of these studies, such as the retrospective design, possible selection bias, the use of BMI as an obesity index, and inadequate adjustment for confounding variables. Main pathophysiologic mechanisms related to obesity that could explain this phenomenon include higher energy reserves, inflammatory preconditioning, anti-inflammatory immune profile, endotoxin neutralization, adrenal steroid synthesis, renin-angiotensin system activation, cardioprotective metabolic effects, and prevention of muscle wasting. The survival benefit of obesity in critical illness is supported from large meta-analyses and recent studies. Due to important methodological limitations, more prospective studies are needed to further elucidate this finding, while future research should focus on the pathophysiologic role of adipose tissue in critical illness.