Introduction: Obesity has emerged as a significant independent predictor of severity in pandemic influenza A (H1N1)pdm09. The aim of this study was to investigate the association between body mass index (BMI) and the risk of hospitalization due to influenza. Methods: Hospitalized patients (n = 755) with laboratory-confirmed influenza were individually matched by age, admission/visit date, and province with an outpatient (n = 783) with laboratory-confirmed influenza and an outpatient control (n = 950). We compared the BMI using conditional logistic regression adjusted for potential confounding factors (aOR). The population attributable fraction (PAF) was calculated. Results: A higher BMI was associated with an increased risk of hospitalization compared to both outpatient cases (aOR = 1.11; 95% CI: 1.07-1.16) and outpatient controls (aOR = 1.04; 95% CI: 1.01-1.07). Compared with normal weight, obesity type I, obesity type II and obesity type III was associated with a greater likelihood of hospitalization compared with outpatient cases (aOR = 1.85, 95% CI: 1.05-3.26; aOR = 5.24, 95% CI: 1.94-14.15 and aOR = 44.38, 95% CI: 4.47-440.5). Compared with normal weight, obesity type II and obesity type III was associated with a greater likelihood of hospitalization compared with outpatient controls (aOR = 4.37, 95% CI: 1.79-10.69 and aOR = 4.95, 95% CI: 1.45-16.87). In persons without influenza vaccination, all categories of BMI ≥ 30 kg/m2 were associated with a greater likelihood of hospitalization compared with normal weight in both outpatient cases and outpatient controls. The PAF of hospitalization by influenza due to BMI ranged from 21.9% to 8.5%; in the case of unvaccinated against influenza between 20.5% to 16.9%. Conclusion: A high BMI is associated with an increased risk of hospitalization due to influenza. High percentage of hospital admissions are attributable to their BMI, especially in non vaccinated.
- Body mass index
- Case control study
- Hospitalization risk
- Population attributable fraction
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine