Association of Obesity and Body Composition and Hospitalization Risk with Infection in the CRIC Study

Key Points Obesity is prevalent in people with CKD and may be a risk factor for developing serious infections. Among people with CKD, both obesity and underweight were significantly associated with the risk of infection. There was a strong association of obesity with skin infection, relative to other infection subtypes, which warrants further investigations. Background People with CKD are at high risk of infection, potentially as a result of impaired immune function. Obesity is prevalent in people with CKD and may be a risk factor for developing serious infections. Methods In 5499 participants of the Chronic Renal Insufficiency Cohort Study, we examined the association of measures of obesity and body composition with time to first hospitalization with infection, defined by hospital discharge records with a diagnostic code for major infections. Body mass index was categorized as underweight (<18.5 kg/m 2 ), normal weight (18.5–24.9), overweight (25.0–29.9), and class 1 (30.0–34.9); class 2 (35.0–39.9); and class 3 (≥40.0) obesity. Measures of body cell mass ( i.e ., phase angle) and tissue hydration status ( i.e ., vector length), assessed with bioelectrical impedance, were grouped into quartiles. We used multivariable Cox models to estimate adjusted hazard ratios (aHRs) of all-cause infection, as well as by infection subtypes. Results During follow-up (median, 4.7 years), 2913 participants had hospitalization with infection. Compared with normal weight, class 3 obesity and underweight were both associated with a higher risk of all-cause infection (aHR, 1.35; 95% confidence interval [CI], 1.16 to 1.57 and 1.76; 95% CI, 1.06 to 2.93, respectively). Compared with the highest quartile, the lowest quartiles of phase angle and vector length were significantly associated with a higher risk of all-cause infection (aHR, 1.39; 95% CI, 1.22 to 1.57 and 1.17; 95% CI, 1.02 to 1.33, respectively). When the analysis was separately performed by infection subtypes, the association of obesity was particularly strong for skin and soft tissue infection (aHR, 1.98; 95% CI, 1.54 to 2.54), but not for others ( e.g ., aHR for lower respiratory tract infection, 0.96; 95% CI, 0.77 to 1.19), whereas underweight and shallow phase angle were broadly associated with the risk of infection across subtypes. Conclusions Among people with CKD, both obesity and underweight were significantly associated with the risk of infection. The association of obesity with skin infection, relative to other infection subtypes, warrants further investigations.