Critically Ill Children More Likely to Die When Underweight, but Not When Obese

By Linda Carroll

July 07, 2020

(Reuters Health) - Being underweight may raise mortality risk among children who are critically ill, but being overweight appears to have no impact, a new study suggests.

In an analysis of data from nearly 4,000 critically ill patients, researchers found that among children and young adults who were underweight, 28-day mortality risk was nearly twice that of normal-weight patients, according to the results published in Pediatrics.

The researchers initially expected that being overweight or obese could raise the risk of death, but it had no statistically significant impact on mortality, they report.

It's not clear why underweight children and young adults are at higher risk.

"We don't know if there is underlying malnutrition or if it's just a matter of low muscle mass or low fat mass or if multiple factors increased the risk," said Dr. Jennifer Kaplan, an associate professor in the division of critical care medicine at the Cincinnati Children's Hospital and Medical Center, in Ohio. "Certainly when someone is critically ill the body needs a lot more energy to support essential organs. Not having enough fat tissue may lead to depleted energy stores and that could be one factor that is important."

To take a closer look at the impact of weight on mortality risk in critically ill patients, Dr. Kaplan and her colleagues analyzed data from the Assessment of Worldwide Acute Kidney Injury, Renal Angina and Epidemiology (AWARE) study, which for three consecutive months recruited all patients aged 3 months to 25 years with a pediatric intensive care unit stay of at least 48 hours in 32 PICUs from Asia, Australia, Europe and North America.

The AWARE database includes information about patient epidemiology, admission diagnoses, comorbidities, and short term outcomes.

Patients in the database were grouped into four categories, by weight - underweight, normal weight, overweight and obese - on the basis of BMI, which was adjusted for age and gender. Out of the 3,719 patients, 1,059 (29%) were classified as underweight, 1,649 (44%) as normal weight, 423 (11%) as overweight and 588 (16%) as obese.

The new study's primary outcome was 28-day mortality. Secondary outcomes included length of ICU stay, presence and duration of mechanical ventilator support, use of vasoactive agents and occurrence of acute kidney injury.

Kaplan and her colleagues looked at both the group of 3,719 patients as a whole and a subset of 542 who had a primary diagnosis of sepsis. The 28-day mortality rate was 3.8% for the entire cohort and 9.1% for the sepsis sub-cohort. In both groups, the mortality rates varied significantly by weight status.

Overall, the 28-day mortality rate was 5.8% among those who were underweight, 3.1% among those who were normal weight, 2.2% among those who were overweight and 1.8% among those who were obese. In the sub-cohort, 28-day mortality was 15.4% among those who were underweight, 6.6% who were normal weight, 3.6% among those who were overweight and 4.7% among those who were obese.

Adjusted 28-day mortality risk was 1.8-fold higher in the underweight group compared with the normal weight group in the overall cohort, and 2.9-fold higher in the sepsis cohort.

Underweight patients also had longer ICU stays, increased need for mechanical ventilation support, and a higher frequency of fluid overload.

The new study may alert doctors to how risky it is for critically ill children and young adults to be underweight, Kaplan said. "One of the things I learned from this study is that we should be paying more attention to these patients," she added. "They are at much higher risk than I initially thought. We should be looking at weight status as a risk factor for bad outcomes."

Dr. Diana Lee was surprised by the new findings.

"Previous studies have shown that both ends of the spectrum are at risk of worse outcomes," said Dr. Lee, a pediatric hospitalist and assistant professor of pediatrics at the Icahn School of Medicine at Mount Sinai and the Mount Sinai Kravis Children's Hospital in New York City. "This study found that children who were overweight or obese were not at increased risk."

Being underweight can be a sign of chronic illness or malnutrition, Dr. Lee said, adding that it would be helpful to have more details on the health of the thinner children and young adults.

Nevertheless, Dr. Lee said, "the study adds a certain level of awareness. If I had an underweight child who was critically ill in the hospital, I might be more alert to whether they were getting fluid overload, for example."

SOURCE: Pediatrics, online July 3, 2020.