Increasing Age Has Limited Impact on Risk of Infection in an Elderly Population.

BACKGROUND

Numerous studies have found increased risk of infection (CDI) with increasing age. We hypothesized that increased CDI risk in an elderly population is due to poorer overall health status with older age.

METHODS

A total of 174 903 persons aged 66 years and older coded for CDI in 2011 were identified using Medicare claims data. The comparison population consisted of 1 453 867 uninfected persons. Potential risk factors for CDI were identified in the prior 12 months and organized into categories, including infections, acute noninfectious conditions, chronic comorbidities, frailty indicators, and health care utilization. Multivariable logistic regression models with CDI as the dependent variable were used to determine the categories with the biggest impact on model performance.

RESULTS

Increasing age was associated with progressively increasing risk of CDI in univariate analysis, with 5-fold increased risk of CDI in 94-95-year-old persons compared with those aged 66-67 years. Independent risk factors for CDI with the highest effect sizes included septicemia (odds ratio [OR], 4.1), emergency hospitalization(s) (OR, 3.9), short-term skilled nursing facility stay(s) (OR, 2.7), diverticulitis (OR, 2.2), and pneumonia (OR, 2.1). Exclusion of age from the full model had no impact on model performance. Exclusion of acute noninfectious conditions followed by frailty indicators resulted in lower c-statistics and poor model fit. Further exclusion of health care utilization variables resulted in a large drop in the c-statistic.

CONCLUSIONS

Age did not improve CDI risk prediction after controlling for a wide variety of infections, other acute conditions, frailty indicators, and prior health care utilization.