Obesity and risk of infections: Results from men and women in the Swedish National March Cohort

Background: Previous studies have shown an association between body mass index (BMI) and infections, but the literature on type-specific community acquired infections is still limited. Methods: We included 39 163 Swedish adults who completed a questionnaire in September 1997 and were followed through record-linkages until December 2016. Information on BMI was self-reported and infections were identified from the Swedish National Patient Register using International Classification of Diseases (ICD), Tenth Revision (ICD-10) codes. We fitted multivariable Cox proportional hazards models for time-to-first-event analysis, and we used extensions of the standard Cox model when repeated events were included. Results: During a 19-year follow-up 32% of the subjects had at least one infection requiring health care contact, leading to a total of 27 675 events. We found an increased incidence of any infection in obese women [hazard ratio (HR) = 1.22; 95% confidence interval (CI) = 1.12; 1.33] and obese men (HR = 1.25; 95% CI = 1.09; 1.43) compared with normal weight subjects. For specific infections, higher incidences were observed for skin infections in both genders (HR = 1.76; 95% CI = 1.47; 2.12 for obese females and HR = 1.74; 95% CI = 1.33; 2.28 for obese males) and gastrointestinal tract infections (HR = 1.44; 95% CI = 1.19; 1.75), urinary tract infections (HR = 1.30; 95% CI = 1.08; 1.55) and sepsis (HR = 2.09; 95% CI = 1.46; 2.99) in obese females. When accounting for repeated events, estimates similar to the aforementioned ones were found. Conclusions: Obesity was associated with an increased risk of infections in both genders. Results from multiple-failure survival analysis were consistent with those from classic Cox models.