Gout not induced by diuretics in a case-control study in general practice

OBJECTIVE: To determine the relation between diuretics and the development of gout, taking into account the possible confounding by hypertension and cardiovascular diseases. DESIGN: Case-control study. METHOD: With the aid of the data on morbidity and medication from the electronic medical files ofa dispensing general practitioner, all patients with a first gout registration during the period from October 1994 to September 2002 were identified as cases; in the same practice, for each patient, 3 controls of the same age and sex who were known not to have gout were selected at random. Conditional logistic regression analyses were carried out to estimate the odds ratio (OR) for gout in patients who had used diuretics for at least 3 months and in patients suffering from hypertension, heart failure, or myocardial infarction. The statistical interaction between variables was investigated after stratification for diuretic use. RESULTS: Via the medical files, 70 gout patients (59 men), with a mean age of 55.1 years (SD: 13.5) were identified, plus 210 matched controls. When assessed without correction, the use ofdiuretics seemed to be associated with a definite risk of gout: OR: 2.8 (95% CI: 1.2-6.6). But after adjustment for the cardiovascular variables hypertension, heart failure and myocardial infarction, the risk of gout associated with diuretic use disappeared: OR: 0.6 (95% CI: 0.2-2.0). An independent risk of gout was demonstrated for hypertension (OR: 3.9; 95% CI: 1.6-10.0), and to a lesser degree for myocardial infarction (OR: 1.5; 95% CI: 0-5-4.1). The risk of gout associated with heart failure was also calculated (OR: 40.1; 95% CI: 3.8-437.2), but diuretic independency could not be proven as all patients with heart failure were on diuretics and there was no heart failure among those not using diuretics. CONCLUSION: In this case-control study, the use of diuretics did not increase the risk of gout. The cardiovascular indications for prescribing diuretics were significant confounders.