Risk factors for surgical site infections in older people

OBJECTIVES: To identify risk factors for surgical site infection (SSI) in older people and to test a priori hypotheses regarding particular variables and SSI risk. DESIGN: Case-control study. SETTING: Duke University Medical Center and seven community hospitals in North Carolina and Virginia. PARTICIPANTS: Elderly patients ( >= 65) who underwent surgery between 1991 and 2002 at the study hospitals. Cases were elderly patients with SSI; controls were elderly operative patients without SSI. Infection control practitioners prospectively identified patients. MEASUREMENTS: Data were collected retrospectively. Case patients who developed SSI were compared with control patients who did not develop SSI. RESULTS: Five hundred sixty- nine SSI cases were identified, and 589 uninfected controls were selected. In multivariate analysis, independent predictors of SSI included obesity (odds ratio (OR) = 1.77, 95% confidence interval (CI) = 1.34 - 2.32), chronic obstructive pulmonary disease (COPD) (OR = 1.66, 95% CI = 1.17 - 2.34), and a wound class classified as contaminated or dirty (OR = 1.65, 95% CI=1.01 - 2.72). Having private insurance was associated with lower risk (OR=0.29, 95% CI = 0.12 - 0.68). CONCLUSION: This study identified several independent predictors of SSI in older people, including comorbid conditions (COPD and obesity), perioperative variables (wound class), and socioeconomic factors (private insurance, which was associated with lower risk). The results from this study can be used to design and implement interventions for SSI prevention in high- risk older people.