Investigating the associations between a dual diagnosis of malnutrition and obesity and length of stay, readmissions, and 12-month mortality in patients aged >65yrs admitted to hospital - a retrospective observational single-centre study

Objective: Despite the protective effect of obesity on mortality in older patients, the dual diagnosis of obesity and malnutrition may worsen outcomes. This study aimed to investigate whether obese patients aged 65 years and over with a diagnosis of malnutrition have different outcomes to obese, non-malnourished peers.

Methods: This retrospective study of inpatients included 9 years of data from annual Malnutrition Audits (2011- 2019). Obesity was defined as Body Mass Index (BMI) >30kg/m²; malnutrition was defined by Subjective Global Assessment (SGA) category B or C. Logistic regression analyses were used to consider the association between a concurrent diagnosis of malnutrition and obesity and outcomes including: 12-month mortality, prolonged length of stay (defined as >50^th centile, very prolonged as >75^th centile) and hospital readmission within 12 months.

Results: 326 obese patients aged 65yrs and over were included. Median patient age was 76.1yrs, with 51.8% female. 37 patients (11%) were malnourished and obese, with a median BMI of 32.9kg/m². Malnutrition increased the odds of prolonged length of stay (OR:3.30, 95% CI 1.58 - 6.91, p = 0.002) and very prolonged length of stay (OR: 4.17, 95% CI 1.89 - 9.21, p = <0.001), as well as increased 12-month mortality (OR: 2.89, 95% CI 1.40 - 5.96, p = 0.004). Malnutrition was not associated with increased hospital presentations within 12 months (p = 0.531).

Conclusion: Older patients with a dual diagnosis of obesity and malnutrition have worse outcomes than their obese but non-malnourished peers. The presence of obesity should not preclude the assessment of nutritional status in older patients.