Lower body mass index is associated with hospital mortality in critically ill Japanese patients

A recent observational study conducted in European intensive care units (ICU) showed that body mass index (BMI) is associated with mortality. We hypothesized that a lower BMI amongst critically ill Japanese patients was associated with increased hospital mortality, similar to findings noted among critically ill European patients. Therefore, we retrospectively investigated the relationship between BMI and patient outcomes in an ICU.

We included consecutive patients who were admitted to our ICU between January 2012 and December 2013. Patients were divided into 3 groups based on their BMI at ICU admission. The underweight ("lower") group (group L) included patients with a BMI below 18.5 kg/m(2), the normal weight group (group N) included patients with a BMI between 18.5 and 24.9 kg/m(2), and the overweight/ obese ("higher") group (group H) included patients with a BMI above 25.0 kg/m(2). Patient data were retrospectively obtained from electronic patient records.

A total of 1,616 patients were admitted to our ICU. Of these patients, 346 patients were ineligible, and therefore, 1,270 were included in the analysis. There were 169 patients in group L, 779 patients in group N and 322 patients in group H. Overall, the mortality rate was 8.1% and the median hospital stay was 21 days. The mortality rate in group L was significantly higher than that in both group N and group H (13.6% vs 7.8% vs 5.9%, p=0.01).

Our retrospective study suggests that lower body mass index may be associated with increased hospital mortality in critically ill Japanese patients.