Prior national epidemiological investigations demonstrated considerable increases in CDI incidence over the last decade [
3,
15,
16]; however, this is the first study to document the national burden of CDI longitudinally among different age groups. This report identified a disproportionate rise in CDI incidence among elderly adults, with an estimated 61% rate of increase from 2001 to 2010. Notably, elderly adults also suffered significantly higher all-cause, in-hospital mortality and increased hospital LOS compared to adult and pediatric patients.
Several factors could contribute to the disparate CDI incidence increase and health outcomes among the elderly compared to other age groups. Advanced patient age has been previously linked to an increase risk for CDI development. This is likely attributed to innate and iatrogenic changes such as: immunosenescence [
17], higher prevalence of comorbid illness [
18], changes in the gut flora [
17], more healthcare exposures (e.g
., hospitalizations and long-term care facility residence), and exposure to antibiotics [
19] and other medications (e.g
., proton pump inhibitors [PPIs]) [
20]. In recent years, there has been an increase in the use of certain antibiotics, particularly among the elderly. Lee et al. [
21] demonstrated an increase in overall antibiotic use in older adult patients by 30% and use of broad spectrum antibiotics in elderly adults by 68% from 2000 to 2010. Furthermore, two meta-analyses suggest that PPI use is associated with increased risk for CDI [
22,
23]. Often, patients take PPIs inappropriately [
24,
25]. Choudhry et al. [
25] found that in a predominately elderly population (median age 76 years), more than half (53.4%) were prescribed a PPI without an appropriate indication. Furthermore, 7.9% were prescribed a PPI for unknown reasons. In addition, there has been a dramatic increase in the use of PPIs among outpatients in the U.S. A 2013 study by Rotman et al. [
24] found that the use of PPIs more than doubled among outpatients in the U.S. between 2002 and 2009.
The poorer health outcomes among elderly patients with CDI could be due to several factors. First, the European and North American CDI guidelines report age over 65 years as a marker of severity [
26,
27]. Severity of infection has been previously linked with increased patient mortality, as well as longer hospital LOS [
28]. Additionally, a prior study demonstrated an increased risk of severe infection and death due to the more pathogenic
C. difficile strain, BI/NAP1/027 strain in elderly adults compared to younger populations [
29].
Our study findings are important for several reasons. First, in 2001, elderly adults represented approximately 13% of the U.S. population. During our study period, there was an addition of approximately five million elderly adults to the U.S. population [
30]. By the year 2030, it is expected that elderly adults will grow to 19% of the total U.S. population. As the population ages, a greater proportion of Americans become high-risk for developing CDI. The incidence and health outcome trends elucidated in our study may help increase awareness of CDI, identify and protect high risk patients, and possibly reduce the occurrence of CDI in the hospital setting.