Contraceptive methods: selective factors in a study of dysplasia of the cervix

Double standards, scientific methods, and epidemiologic research

Because suspected noxious agents can seldom be tested experimentally in people, epidemiologic investigation of the causes of disease depends on observational procedures, of which the most prominent types are cohort and case-control studies. In these studies the compared agents cannot be assigned experimentally, but many other basic experimental principles that could be employed are often overlooked, including verification of quality and accuracy in raw data, avoidance of major biases in comparison, vigilance in checking for methodologic errors, and maintenance of a careful distinction between research data that generate hypotheses and the new data needed to test these hypotheses. The problems that result when these principles are overlooked can be alleviated if etiologic research is performed and evaluated with the same standards used in other branches of science.

Oral contraceptive use: association with frequency of hospitalization and chronic disease risk indicators

A questionnaire was mailed to 97,364 married women, aged 26--50, resident in Greater Boston in 1970, requesting information on lifetime oral contraceptive (OC) use, reproductive history, education, and hospitalization experience in 1969; 65,843 women responded. In 1973 a second questionnaire was mailed to 37,292 of these women, including all OC users and an equal number of non-users matched on age, parity, education, and town of residence. This questionnaire related to use of OCs, other female hormones, and the menopause. OC use was most strongly related to age, with a sixfold increase in use from the oldest women (of whom 10 per cent had used OCs at some time) to the youngest. Use was directly related to education and mobility and inversely related to parity. Reasons for beginning and ceasing use differed for women of different ages and educational attainment. Thus, use of OCs varies with social and reproductive characteristics that are risk indicators for many diseases. OC use was associated with increased risk of hospitalization for thromboembolic disease (risk ratio = 1.5, 95 per cent confidence limits 1.2, 3.2) and for mental illness, hyperthyroidism, hypertension, and cancer of the cervix. OC users were hospitalized for many non-life threatening conditions 20 to 40 per cent more frequently than were non-users.

Oral contraceptives and cervical carcinoma

In a case-control study, 689 consecutive patients with cervical carcinoma were studied for their use of oral contraceptives. The control patients were matched for age, ethnic origin, age at first pregnancy, age at first coitus, and socioeconomic status. There was no significant difference between case and control subjects in the duration or oral contraceptive use, the type of estrogen used, or the years in which oral contraceptives were used. The mean duration of oral contraceptive use was 30.9 months by the case subjects and 30.2 months by the control subjects.

Contraceptive choice and prevalence of cervical dysplasia and carcinoma in situ

Whether use of oral contraceptives is associated with subsequent development of cervical neoplasia is an important public health question. Before evaluating this issue, we must determine if choosing oral contraceptives identifies a woman who is intrinsically at high risk of developing cervical neoplasia. We have examined the demographic and reproductive characteristics as well as cervical premalignant changes manifest by 15- to 44-year-old black women who enrolled in a public family-planning clinic. When compared to IUD acceptors, oral contraceptive acceptors did not have a disproportionately large number of women with traits which predicted for high risk of developing cervical neoplasia. Oral contraceptive acceptors, compared to IUD acceptors, did not have a higher prevalence rate of carcinoma in situ. Oral contraceptive acceptors with no Pap smears prior to initial choice of contraceptive method did have a 1.4-fold higher prevalence rate of cervical dysplasia than IUD acceptors. These results suggest that the deicision to use oral contraceptives, per se, does not identify a group of women at higher risk to develop cervical carcinoma in situ. Such a decision may, however, identify a group with a small increased propensity for developing cervical dysplasia.