Characteristics of Hospitalised Patients at the Lowest and Highest Ends of the Body Mass Index Spectrum

Background: Recent findings established that underweight (UW) and extremely obese (EO) people were over-represented in the inpatient cohort of one Australian tertiary hospital. This study aimed to describe the characteristics of these patients and identify if differences existed between this subset and the remaining cohort. Method: Single-centre retrospective case-note review of patients previously identified as being UW or EO during a 2015 prospective point prevalence study, and comparison with those who had “closer-to-normal-weight” body mass index (BMI). Results: Forty eight patient notes were reviewed (33 UW; 15 EO). The majority of UW patients were admitted under General Medicine with cancer-related illness, whereas EO patients were admitted across specialties, most commonly with a cardiovascular condition. The most frequent past medical history for both groups was a cardiovascular disorder. Compared to patients in all other BMI categories, there was no higher risk of prolonged hospital length of stay in either patient group (p = 0.94). Underweight patients had significantly higher age-adjusted Charlson co-morbidity index scores compared to the EO group (p = 0.01), and although not statistically significant, there was higher frequency of mortality (in-hospital, 28-day and 1-year post-discharge) in those UW (p = 0.54; p = 1; p = 1 respectively). Both groups demonstrated higher rates of hospital re-admission within 28 days of discharge than those reported for this hospital as a whole. Conclusion: Data presented adds to the limited evidence relating to health outcomes for patients at either end of the BMI spectrum. Decreasing hospital re-admission frequency in these groups might result in considerable cost savings in the future.