Hospitalization for Clostridium Difficile in the US Elderly: Co-morbidity and Seasonal Drivers

In the US, over 300,000 cases of Clostridium difficile associated diarrhea occur annually in hospitals or long-term care facilities and incidence has risen over the past two decades. Though C. difficle is considered to be a hospital acquired disease, we have demonstrated a clear seasonal pattern which may indicate a strong environmental influence. C. difficle seasonality can also be driven by co-morbid conditions or infections with well defined seasonal patterns. All 1,054,125 hospitalization records for the US elderly with C. difficile were abstracted from the Centers for Medicare and Medicaid Services (CMS) database for a 14-year period (1991-2004). The most common co-morbid conditions, identified using the Elixhauser categorization scheme, were fluid and electrolyte disorders (429,152 cases, 40.7%) and hypertension (349,522 cases, 33.2%). Seasonality was assessed for the subset of cases with electrolyte disorders and hypertension, both of the co-morbid peaks were closely aligned to the peak for C. difficle. Several C. difficle cases also reported gastrointestinal symptoms (ICD 787,558.9) (62,687 cases, 5.95%) and ill-defined intestinal infections (ICD 008.5,008.8,009) (2358 cases, 0.2%). We tested whether these gastrointestinal conditions may drive seasonality of C. difficle. All hospitalization records for gastrointestinal symptoms and ill-defined intestinal infections were extracted from the complete hospitalization dataset and seasonality was assessed. The peak for both gastrointestinal symptoms and ill-defined intestinal infections precedes the peak in C. difficile (31st and 30th, respectively vs. 34th calendar week). These results suggest that the seasonal pattern seen in C. difficile may be driven by hospitalization for other intestinal infections.