Benign breast disease and consumption of beverages containing methylxanthines.

The relationship between methylxanthine (Mx) consumption and benign breast disease was evaluated in a case-control study of 288 women with histologically confirmed benign breast lumps (203 dysplastic lesions and 85 benign tumors) and 2 groups of control women--285 patients in the hospital for acute conditions apparently unrelated to the consumption of Mx-containing beverages and 291 outpatients. The relative risk estimates of dysplastic breast lesions (fibrocystic disease), with allowance for all identified potential distorting factors, for women who drank 1-2 or 3 or more cups of coffee per day were 4.1 and 6.4, respectively, when the hospital controls were the comparison group and 2.0 and 3.7, respectively, when the outpatient controls were the comparison group. The relationship was even stronger when the total consumption of Mx-containing beverages (coffee plus tea) was considered and increased with increasing duration of use. The association was not explained by any of the major risk factors for fibrocystic breast diseases or by differences in general characteristics or other lifestyle habits between cases and controls. Mx consumption was not related to the risk of benign breast tumors (fibroadenomas). These findings support the hypothesis that Mx consumption is related to the risk of dysplastic lesions of the breast.