title: Respiratory tract infections and subsequent risk of chronic lymphocytic leukemia.
abstract: Recent evidence suggests that chronic lymphocytic leukemia (CLL) might occur following a response to an infectious agent. We conducted a population-based study including 4249 CLL patients diagnosed in Denmark from 1977 to 1997 and 15 690 frequency-matched controls to quantify risk of CLL following various airway infections. Through data linkage we gathered information on hospital inpatient/outpatient discharges that listed infections present at least 1 year prior to CLL. Using logistic regression, we calculated odds ratios (ORs) and 95% confidence intervals (CIs). Personal history of pneumonia was associated with significantly increased CLL risk (OR = 1.4; 1.2-1.8); risk was restricted to 1 to 4.99 years prior to CLL diagnosis (OR = 1.6; 1.2-2.0). Individuals with 3 or more prior pneumonia events had a significant 2.5-fold (1.1-5.6) elevated CLL risk, and risk increased with the number of pneumonia episodes (P(trend) < .001). None of 9 other respiratory-tract infections was significantly associated with CLL risk. Pneumonia might be a potential CLL trigger or it could represent premalignant immune disruption preceding CLL.
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20892-7236, USA. landgreo@mail.nih.gov
authors.forename: Ola
authors.initials: O
authors.lastname: Landgren
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Rapkin
authors.forename: Neil E
authors.initials: NE
authors.lastname: Caporaso
authors.forename: Lene
authors.initials: L
authors.lastname: Mellemkjaer
authors.forename: Gloria
authors.initials: G
authors.lastname: Gridley
authors.forename: Lynn R
authors.initials: LR
authors.lastname: Goldin
authors.forename: Eric A
authors.initials: EA
authors.lastname: Engels
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000145:classification / Q000453:epidemiology / Q000209:etiology* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D012141:Respiratory Tract Infections / Q000150:complications* / Q000453:epidemiology / Q000276:immunology / Q000473:pathology*; D012307:Risk Factors