Agreement between women's histories of oral contraceptive use and physician records

The ability of women to recall their oral contraceptive histories

Self-reported contraceptive histories were obtained at interview from 99 women and compared with prospectively collected data from the Oxford-Family Planning Association cohort study. The effect of different memory aids was evaluated and an assessment was made of the completeness and accuracy of contraceptive histories recorded in general practice notes. Accuracy of recall of total duration of use was sufficiently good to establish the presence or otherwise of a duration-response relationship and could be improved by the use of a contraceptive calendar. Recall of specific brands used was less accurate. In studies where accurate information on use of particular preparations is required, the use of a photo album is recommended, supplemented by data obtained from general practice records to improve the accuracy of dates. General practice records on their own are not sufficiently complete to be used as a sole source of exposure data in studies in which it is important to obtain a complete oral contraceptive history.

Observational studies of cause-effect relationships: an analysis of methodologic problems as illustrated by the conflicting data for the role of oral contraceptives in the etiology of rheumatoid arthritis

We review the structure of the two most common observational study designs, cohort and case-control studies, and outline guidelines to help clinicians evaluate the validity of studies that employ these designs. To demonstrate the use of these guidelines we apply them to the important issue of whether oral contraceptive usage may reduce the risk of developing rheumatoid arthritis. A recent case-control study has contradicted provocative evidence from two previous studies suggesting the existence of such a protective effect. Our analysis leads to the conclusion that the case-control study suggesting no association of oral contraceptives with the subsequent development of rheumatoid arthritis provides the best estimate of the effect of oral contraceptives currently available, and furthermore, the analysis permits recommendations to be made for the design of future investigations on this topic.

Oral contraceptives and cardiovascular disease: a critique of the epidemiologic studies

Observational study designs used to investigate the relationship of oral contraceptive use to the occurrence of venous thromboembolism, stroke, myocardial infarction, and cardiovascular death include case-control, cohort, and mortality statistics studies. This analysis catalogs the findings of each of these epidemiologic studies, its statistical significance, and its performance with regard to scientific methodologic standards. An association between current oral contraceptive use and incidence of venous thromboembolism without predisposition has been consistently observed in case-control and cohort studies. Associations are less consistent for various types of stroke and for myocardial infarction. Only the Royal College of General Practitioners study found a significantly elevated risk of cardiovascular death with oral contraceptive use. The majority of mortality statistics studies offer little support for a relationship between oral contraceptive use and cardiovascular events. Major systematic problems in the epidemiologic studies include potential for bias in the detection of cardiovascular events and differences in the prognostic susceptibility of compared groups. Bias in the ascertainment of drug exposure is an unresolved issue for most of the case-control studies. Because of possible biases arising from methodologic deficiencies in these epidemiologic studies, questions as to the validity of the observed associations between oral contraceptive use and cardiovascular events should remain.