RELATION OF PULMONARY LYMPHANGIOLEIOMYOMATOSIS TO USE OF THE ORAL-CONTRACEPTIVE PILL AND FERTILITY IN THE UK - A NATIONAL CASE-CONTROL STUDY

Background - Pulmonary lymphangioleiomyomatosis is a rare progressive disease of unknown aetiology affecting premenopausal women. Since the oral contraceptive pill has been implicated in its pathogenesis, a case control study was carried out to determine whether women with the disease were more likely to have taken the oral contraceptive pill, and whether the disease was associated with other conditions related to sex hormones including pregnancy, parity, and fibroids. Methods - All chest physicians in the UK were asked for details of all live patients with pulmonary lymphangioleiomyomatosis; the patient's family doctor was then asked for four age and sex matched control subjects from their patient register. Details of lifetime use of the oral contraceptive pill, pregnancy, parity, history of fibroids, and smoking were obtained from cases and controls. Relative odds of exposure to potential risk factors were estimated by conditional logistic regression. Results - Medical details were obtained from all 23 cases of lymphangioleiomyomatosis identified; questionnaires were completed by 21 cases (one by proxy) and by 46 matched controls of mean (SD) age 43 (10) and 44 (11) years, respectively. The patients had a mean age of 34 (9) years at onset of symptoms and a median (range) time of 2 (0-29) years from onset of symptoms to diagnosis. Compared with control subjects, cases did not differ in the use of the oral contraceptive pill (odds ratio (OR) 0.39, 95% CI 0.09 to 1.68), diagnosis of fibroids (OR 3.12; 95% CI 0.52 to 18.7), age of menarche, menstrual history, or lifetime smoking. They were, however, less likely to have been pregnant (OR 0.14, 95% CI 0.03 to 0.71) or to have had children (OR 0.13, 95% CI 0.03 to 0.67). More pregnancies had ended in spontaneous abortion (28% v 8%) but the proportion of women undergoing spontaneous abortion was similar in cases and controls (OR 2.13, 95% CI 0.47 to 9.3). Conclusions - This study does not support the hypothesis that use of the oral contraceptive pill is causally associated with the development of pulmonary lymphangioleiomyomatosis. Sex hormones may be involved, however, since patients were less likely to have been pregnant or to have had children, and tended to have had more spontaneous abortions and an increased incidence of fibroids.