Common community acquired infections and subsequent risk of chronic lymphocytic leukaemia

Emerging evidence supports a role for immune-related factors in the causation of chronic lymphocytic leukaemia (CLL). Using the population-based U.S. Surveillance Epidemiology and End Results-Medicare database, 10 171 elderly CLL patients and 122 531 frequency-matched controls were identified in order to evaluate several community acquired infections associated with subsequent CLL risk. Odds ratios (ORs) were adjusted for gender, age, race, calendar year and number of physician claims. CLL risk was increased following Medicare claims for sinusitis (OR = 1·11; 95% CI = 1·05–1·17), pharyngitis (OR = 1·15; 1·08–1·22), bronchitis (OR = 1·14; 1·08–1·19), pneumonia (OR = 1·17; 1·11–1·24), influenza (OR = 1·10; 1·01–1·19), cellulitis (OR = 1·08; 1·02–1·14) and herpes zoster (OR = 1·26; 1·15–1·37). Associations with pneumonia and cellulitis remained significant when the 5-year period before diagnosis/control selection was excluded. CLL risk increased with increasing severity/frequency of pneumonia (P = 0·005), cellulitis (P < 0·001) and herpes zoster (P < 0·001). Our findings suggest that common infections may play a role in CLL aetiology. Alternatively, the associations might reflect an underlying immune disturbance present several years prior to CLL diagnosis.