Recent evidence suggests that obesity increases the risk of severe outcomes following respiratory infection. It is less clear whether obesity is associated with the risk of being infected with influenza or other respiratory pathogens. Therefore, we examined the association between obesity and outpatient visits for acute respiratory infections (ARIs).
We conducted a retrospective cohort study for a period of over 13 years on 104,665 individuals in Ontario, Canada who responded to population health surveys and agreed to linkage with health administrative data. Individuals aged 18-64 years who responded to a survey within 5 years prior to the start of an influenza season were included. Poisson regression, with adjustment for relevant confounders, was used to measure the association between self-reported body mass index (BMI) and outpatient visits for ARI. We conducted numerous sensitivity analyses to assess the robustness of our findings.
We observed higher rates of outpatient visits for ARI during influenza season periods compared with normal weight individuals for those who were overweight (BMI 25-29.9; rate ratio (RR) 1.10; 95% confidence interval (95% CI) 1.07-1.13), obese class I (BMI 30-34.9; RR 1.17; 95% CI 1.13-1.22) and obese class II or III (BMI =35; RR 1.19; 95% CI 1.12-1.25). Associations of a similar magnitude were observed during non-influenza season periods. Obesity was a greater risk factor for ARIs managed in emergency departments than physician offices.
Obese individuals are at an increased risk of outpatient visits for ARI during both influenza and non-influenza season periods, suggesting that the effect of obesity on the risk of respiratory infections is not limited to influenza. Interventions designed to reduce the prevalence of obesity may have the added benefit reducing the population burden of respiratory infections.