SAN DIEGO – Underweight people don’t get much attention amid the obesity epidemic. But a new analysis of worldwide data finds that underweight pediatric ICU patients worldwide face a higher risk of death within 28 days than all their counterparts, even the overweight and obese.
Dr. Rajit Basu
While the report suggests that underweight patients weren’t sicker than the other children and young adults, they also faced a higher risk of fluid accumulation and all-stage acute kidney injury, compared with overweight children, study lead author Rajit K. Basu, MD, MS, of Emory University and Children’s Healthcare of Atlanta, said in an interview. His team’s findings were released at Kidney Week 2018, sponsored by the American Society of Nephrology.
“Obesity gets the lion’s share of the spotlight, but there is a large and likely growing population of children who, for reasons left to be fully parsed out, are underweight,” Dr. Basu said. “These patients have increased attributable risks for poor outcome.”
The new report is a follow-up analysis of a 2017 prospective study by the same team that tracked acute kidney injury and mortality in 4,683 pediatric ICU patients at 32 clinics in Asia, Australia, Europe, and North America. The patients, aged from 3 months to 25 years, were recruited over 3 months in 2014 (N Engl J Med 2017;376:11-20).
The researchers launched the study to better understand the risk facing underweight pediatric patients. “There is a paucity of data linking mortality to weight classification in children,” Dr. Basu said. “There are only a few reports, and there is a suggestion that the ‘obesity paradox’ – protection from morbidity and mortality because of excessive weight – exists.”
For the new analysis, researchers tracked 3,719 patients: 29% were underweight, 44% had normal weight, 11% were overweight, and 16% were obese.
The 28-day mortality rate was 4% overall and highest in the underweight patients at 6%, compared with normal (3%), overweight (2%), and obese patients (2%) (P less than .0001). Underweight patients had a higher adjusted risk of mortality, compared with normal-weight patients (adjusted odds ratio, 1.8; 95% confidence interval, 1.2-2.8).
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Underweight patients also had “a higher risk of fluid accumulation and a higher incidence of all-stage acute kidney injury, compared to overweight children,” Dr. Basu said.
The study authors also examined mortality rates in the 14% of patients (n = 542) who had sepsis. Again, underweight patients had the highest risk of 28-day mortality (15%), compared with normal weight (7%), overweight (4%), and obese patients (5%) (P = 0.003).
Who are the underweight children? “Analysis of the comorbidities reveals that nearly one-third of these children had some neuromuscular and/or pulmonary comorbidities, implying that these children were most likely static cerebral palsy children or had neuromuscular developmental disorder,” Dr. Basu said. “The demographic data also interestingly pointed out that the underweight population was predominantly Eastern Asian in origin.”
But there wasn’t a sign of increased illness in the underweight patients. “We can say that these kids were no sicker compared to the overweight kids as assessed by objective severity-of-illness scoring tools used in the critically ill population,” he said.
Is there a link between fluid overload and higher mortality numbers in underweight children? “There is a preponderance of data now, particularly in children, associating excessive fluid accumulation and poor outcome,” Dr. Basu said, who pointed to a 2018 systematic review and analysis that linked fluid overload to a higher risk of in-hospital mortality (OR, 4.34; 95% CI, 3.01-6.26) (JAMA Pediatr. 2018;172[3]:257-68).
Fluid accumulation disrupts organs “via hydrostatic pressure overregulation, causing an imbalance in local mediators of hormonal homeostasis and through vascular congestion,” he said. However, best practices regarding fluid are not yet clear.
“Fluid accumulation does occur frequently,” he said, “and it is likely a very important and relevant part of practice for bedside providers to be mindful on a multiple-times-a-day basis of what is happening with net fluid balance and how that relates to end-organ function, particularly the lungs and the kidneys.”
The National Institutes of Health provided partial funding for the study. One of the authors received fellowship funding from Gambro/Baxter Healthcare.