Previous medical history and medications as risk factors for hairy cell leukaemia.

To investigate the possible role of previous medical history and previous medications as risk factors for hairy cell leukaemia (HCL) we performed a population based case-control study on 121 male HCL patients and 484 controls. The data were collected through a self-administered mailed questionnaire. Elevated odds ratios (OR) were found for a history of appendicitis [OR 1.9; 95% confidence interval (CI) 0.9-4.2] and pneumonia (OR 2.9; CI 0.9-9.6). We found a reduced risk for HCL associated with a history of myocardial infarction (OR 0.3; CI 0.4-2.5), hypertension (OR 0.6; CI 0.3-1.2) and thromboembolic disease (OR 0.6; CI 0.1-2.7). Reduced OR was also associated to a history of diabetes mellitus (OR 0.6; CI 0.1-2.9) and a diagnosis of hyperlipidemia (OR 0.8; CI 0.2-3.6). HCL is an indolent disease with a clinical course of many years and it can not be excluded that the disease leads to metabolic changes, resulting in a changed risk for these diagnoses. When the role of previous medications were investigated, increased OR was found for NSAID (OR 3.4; CI 1.1-10.2). Decreased OR was found for the anti-coagulative agent warfarin (OR 0.4; CI 0.1-1.5). A history of a previous malignancy preceeding the diagnosis of HCL as reported to the Swedish Cancer Registry yielded an increased OR of 3.2 (CI 1.2-8.5). All results must be interpreted with caution, as there is a possibility of misclassification. Medications is difficults to remember, particularly several years after consumption. As many comparisons were made, there is always a possibility of correlations occuring by chance.