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

Some Further Consideration on the Role of Oral Contraceptives in Breast Carcinogenesis

Available evidence concerning oral contraceptives and their potential interaction with reproductive history on breast cancer risk Is reviewed. The relative risks in 15 out of 15 studies were above unity among younger women (i.e., below age 35 and perhaps up to 45) for long-term oral contraceptive use, although apparent heterogeneities emerged in the risk estimates. The overall evidence is reassuring in subsequent age groups, whereas the modifying effects or interactions between oral contraceptives, reproductive factors and breast cancer risk are still largely undefined. Thus we suggest that, besides chance and bias, the apparent discrepancies between various studies should be considered within the framework of the complex time- and age-effects of hormone-related risk factors on breast carcinogenesis.

Lifetime exposure to estrogens and Parkinson's disease in California teachers

INTRODUCTION

Parkinson's disease (PD) is consistently observed to occur less frequently in women than men, prompting investigation into whether estrogen protects against neurodegeneration of dopaminergic neurons.

METHODS

We used baseline data in the California Teachers Study, a prospective cohort of women, to investigate whether reproductive factors indicating higher long-term estrogen levels are associated with PD using a nested case-control approach. We identified 228 PD cases and 3349 unaffected controls frequency matched by age and race.

RESULTS

Women who reported using combined estrogen/progesterone therapy or progesterone only formulations had a 57% increase in PD risk (OR = 1.57, 95% CI = 1.06, 2.34) compared to never having used HT. Compared to women with menopause at 50-52 years, menopause at younger (<35-46 years: OR = 0.59, 95% CI = 0.37, 0.94) and older ages (≥53 years: OR = 0.54, 95% CI = 0.36, 0.83) had lower PD risk. A derived composite estrogen summary score for women's exposure to both endogenous and exogenous estrogens throughout life indicated that women with presumed higher cumulative lifetime levels of estrogen (a score of 3-5) had a significantly reduced PD risk [(OR = 0.57, 95% CI = 0.35, 0.91) relative to those with lower lifetime estrogen exposure or a composite estrogen summary score of 0-1].

CONCLUSIONS

These results provide some support for the hypothesis that lifelong high estrogen is protective in PD, suggesting that the level and persistence of exposure over the long term may be important in PD risk reduction.

Occlusive vascular diseases in oral contraceptive users. Epidemiology, pathology and mechanisms

Despite being an unprecedented departure from normal physiology, the combined oral contraceptive is not only highly effective, but it also has a remarkably good safety record. Concerns over safety persist, though, particularly with regard to venous thromboembolism (VTE), stroke and myocardial infarction (MI). Epidemiological studies consistently show an increase in risk of VTE, but the results are more contentious with regard to arterial diseases. Despite 40 years of research, the mechanisms behind these adverse effects are not understood. In this review, we integrate information from published studies of the epidemiology and pathology of the occlusive vascular diseases and their risk factors to identify likely explanations for pathogenesis in oral contraceptive users. Oral contraceptives induce both prothrombotic and fibrinolytic changes in haemostatic factors and an imbalance in haemostasis is likely to be important in oral contraceptive-induced VTE. The complexity of the changes involved and the difficulty of ascribing clinical significance has meant that uncertainty persists. A seriously under-researched area concerns vascular changes in oral contraceptive users. Histologically, endothelial and intimal proliferation have been identified in women exposed to high plasma estrogen concentrations and these lesions are associated with thrombotic occlusion. Other structural changes may result in increased vascular permeability, loss of vascular tone and venous stasis. With regard to arterial disease risk, epidemiological information relating to dose effects and joint effects with other risk factors, and studies of pathology and changes in risk factors, suggests that oral contraceptive use per se does not cause arterial disease. It can, nevertheless, synergise very powerfully with subclinical endothelial damage to promote arterial occlusion. Accordingly, the prothrombotic effects of the oral contraceptive estrogen intervene in a cycle of endothelial damage and repair which would otherwise remain clinically silent or would ultimately progress - in, for example, the presence of cigarette smoking or hypertension - to atherosclerosis. Future work in this area should focus on modification of the effects of established risk factors by oral contraceptive use rather than modification of the supposed risk of oral contraceptive use by established risk factors. Attempts to understand vascular occlusion in oral contraceptive users in terms of the general features of VTE or with reference to atherosclerosis may be limiting, and future work needs to acknowledge that such occlusions may have unique features. Unequivocal identification of the mechanisms involved would contribute considerably to the alleviation of fears over vascular disease and to the development of even safer formulations.

Hormone replacement therapy and risk for breast cancer

Because breast cancer will develop in one of every nine American women, even a small increase in risk associated with a widespread exposure is of substantial public health concern. Although most studies have not found ever use of estrogens to be a risk factor for breast cancer, it is not yet resolved whether current or long-term users experience some increase in risk. Given the fact that the indications for menopausal estrogen use have changed substantially over time, from short-term use for the relief of menopausal symptoms to long-term use for lifetime reduction of conditions such as cardiovascular disease and osteoporosis, it is imperative that the effects of long-term estrogen replacement on the risk for breast cancer be resolved. These studies are not without associated methodologic difficulties, with the ultimate interpretation of the association possibly dependent on the results of controlled clinical trials. Although such investigations are currently underway, the results will not be available for many years. To address more immediate concerns, continued emphasis should be placed on well-designed case-control and cohort studies. For the results to be reliable, attention must be directed to the effects of selection, recall and surveillance biases, confounding factors, detailed exposure relationships, subgroup variations, and disease associations. In addition, given the increasing trend for estrogens to be prescribed in combination with progestogens, the effects on breast tissue of this combined therapy merit immediate attention.

Employment status and high blood pressure in women: variations by time and by sociodemographic characteristics

PURPOSE

The association between employment status and high blood pressure in women was examined at two time periods to determine if associations between employment status and high blood pressure varied by time period or by age, race, education, marital status, or parental status.

METHODS

Women participants from the National Health Examination Survey (1960) and the Second National Health and Nutrition Survey (1976-1980) between the ages of 25 and 64 and currently employed or keeping house were included. Logistic regression analysis was used to examine the cross-sectional association between employment status and high blood pressure in each survey, taking into account potential effect modifiers and covariates.

RESULTS

In 1960 employment was associated with a slight, but not statistically significant, elevation in odds of high blood pressure. In 1976-1980, it was associated with a modest but significant reduction in odds of high blood pressure. Variations in associations occurred by marital status (protective associations were limited to unmarried women) and race (associations were of stronger magnitude among African-American women).

CONCLUSIONS

The employment status-high blood pressure relationship shifted across surveys. Changes in the composition of the employed and nonemployed groups account for at least part of the varying relationships.

Oral contraceptives and breast cancer: a cooperative Italian study

The relationship between oral contraceptives (OC) and breast-cancer risk was analysed using data from a case-control study conducted between June 1991 and February 1994 in 6 Italian centres on 1,991 patients below age 65 with histologically confirmed incident breast cancer and 1,899 controls admitted to hospital for a wide range of acute, non-neoplastic, non-hormone-related diseases. "Ever OC use" was reported by 18% of cases versus 14% of controls, corresponding to a multivariate odds ratio (OR) of 1.1 (95%) confidence interval, Cl 0.9 to 1.4). The ORs were 1.3 for use lasting < 1 year, 1.1 for 1 to 4 years, 0.9 for 5 to 8 years, and 1.2 for over 8 years. With reference to age at first use, there was some indication that the OR was elevated in women who had started use before age 30, but not in those starting at a later age. With reference to time since last OC use, the OR was above unity for women who had stopped for less than 10 years (1.6 for 1 to 4 years; 1.7 for 5 to 9 years), but the OR declined to unity for women who had stopped OC use for 10 years or longer. The OR for women who had stopped OC use for less than 10 years was consistently elevated across strata of selected covariates, and was directly related to the duration of use (OR 1.3 for < 5 years, 1.7, for > or = 5 years). In contrast, the OR was 0.6, for use lasting > or = 5 years in women who had stopped for 10 years or more. The elevated OR for women who had recently stopped OC use, together with the absence of association (or the suggestion of some protection) for those who had stopped for 10 years or more is consistent with the pattern of breast-cancer risk observed after a full-term pregnancy, and provides important reassurance on a public health level on the long-term impact of OCs on breast carcinogenesis.

Oral contraceptives and non-contraceptive oestrogens in the risk of gallstone disease requiring surgery

STUDY OBJECTIVE

The aim was to investigate the relationship between oral contraceptives, non-contraceptive oestrogens, and the risk of gallstone disease requiring surgery.

DESIGN

This was a hospital based case-control study carried out between 1987 and 1990. Main outcome measures were frequency of consumption of oral contraceptives and non-contraceptive oestrogens, and the corresponding multivariate relative risk estimates and 95% confidence intervals (CI) in relation to various measures of use of the preparations.

SETTING

A network including major teaching and general hospitals in the greater Milan area, northern Italy.

SUBJECTS

Subjects were 235 women with gallstones requiring surgery and 538 controls admitted for acute diseases, other than digestive or hormonal diseases or those potentially influencing the use of female hormone preparations.

MAIN RESULTS

For oral contraceptives, the relative risk for ever use was 0.8 with 95% CI 0.4 to 1.5. With reference to duration of use, the multivariate relative risk was 1.0 for less than two and 0.5 for two or more years of use. The relative risk was 1.7 (95% CI 0.6 to 4.7) in women who had last used the pill less than five years before diagnosis, but declined to 0.4 (95% CI 0.2 to 1.0) in those who had stopped more than five years before. With reference to oestrogen replacement treatment, the relative risk for ever use was 1.9 (95% CI 1.0 to 3.1). The relative risk, however, was not related to duration of use, since it was 1.8 for less than two and 1.5 for two or more years of use. Relative risk was higher for women who had last used non-contraceptive oestrogens 10 or more years before diagnosis (2.4) than for shorter periods since last use (1.3).

CONCLUSIONS

On a clinical and public health scale, oral contraceptives and non-contraceptive oestrogens are unlikely to have an important influence in the aetiology of gallbladder disease.

Oral contraceptive use and risk of cutaneous malignant melanoma in a case-control study of French women

We report the results of a case-control study designed to analyze the relationship between oral contraceptive use (OC) and the risk of cutaneous malignant melonama (MM) in 240 White women under the age of 45. Five French centers participated in the study between February 1982 and January 1987 for periods of eight to 54 months, depending on the center. Cases were 91 consecutive newly diagnosed patients with histologically verified MM. Each case was matched with one or two controls on year of birth, date of interview, and treatment center. Controls were 149 patients with either malignant or nonmalignant disease who came to the center for diagnosis and treatment. Odds ratios (OR) were estimated by multivariate analyses taking into account age at menarche, sunlight exposure, and skin characteristics. No significant relation was found between the risk of MM and the total duration of OC use, age at start of use, and elapsed time since the first OC use. However, when the analysis was restricted to women aged 30-40 years, i.e., those who were able to use OC for 10 years or more, or who had started OC use 15 years or more before the diagnosis, the risk of MM increased significantly with the duration of OC use (P = 0.03). A total of more than 4,000 hours of sunlight exposure, and menarche before the age of 14 also were found to increase significantly the risk of MM (OR = 5.4, 95 percent confidence interval [CI] = 1.6-18.3; and OR = 3.6, CI = 1.0-12.5, respectively).

Oral contraceptives and skin neoplasia

A possible association between oral contraception and the development of cutaneous melanoma has been raised largely because of the hyperpigmentation of pregnancy and the effect pregnancy may have on the outcome of established disease. Present evidence suggests there is no causal link between oral contraceptive (OC) use and melanoma (or with benign melanocytic nevi), nor has a specific subgroup of women or subtype of melanoma been consistently implicated as being at increased risk of this disease due to use of OCs.

Oral contraceptives and cervical neoplasia

Although initial studies examining the relationship of oral contraceptives to risk of cervical neoplasia were reassuring, more recent studies provide some evidence of a positive relationship, particularly for long-term usage. Results, however, are difficult to interpret, because of a variety of methodologic complexities, including potential sources of confounding and bias. Sexual behavior and Pap smear screening have been identified as important confounders, but in several well-controlled studies residual excess risks of nearly 2-fold persist for users of 5 or more years. A possible promotional effect of oral contraceptives is suggested by higher risks associated with recent usage. There also is some suggestion of a stronger effect for adenocarcinomas than for squamous cell tumors. A relationship is biologically possible, given findings of hormone receptors in cervical tissue and the fact that oral contraceptives have been found to induce cervical hyperplasia. In addition, oral contraceptives may induce proliferation of the human papillomaviruses, the leading suspect agent for cervical cancer. Although a number of lines of evidence support a relationship of oral contraceptives to cervical cancer risk, firm conclusions await the results of additional studies that specifically address some of the methodologic shortcomings of previous investigations. In particular, additional follow-up studies are needed to define the effect of oral contraceptives on the natural history of cervical lesions.

Breast cancer and combined oral contraceptives: an Italian case-control study

The risk of breast cancer in relation to use of oral contraceptives was evaluated using data from a hospital-based case-control study from Northern Italy on 1517 cases below age 60 and 1351 controls admitted for acute diseases unrelated to any of the known or potential risk factors for breast cancer. The multivariate relative risk for ever vs. never users was 1.3 (95% confidence interval = 1.0-1.7). However, the risk was not related to duration of use: indeed the highest risk was observed among short-term users (less than 2 years), and the point estimate was 0.9 among users for 5 years or more. The elevated risk among short-term users, if not due to residual confounding or selection mechanisms, is probably explainable in terms of recall bias (i.e. more careful report of short or very short use by cases). No definite pattern was observed in relation to latency or recency of use, and the point estimates were 0.8 for women who had ever used the pill before age 25 and 0.8 for those who had ever used the pill before first full-term pregnancy. Thus, the study presents further reassuring information on the oral contraceptive/breast cancer debate. Its major limitation lies in the low prevalence of oral contraceptive users in Italy, with a consequently reduced statistical power, although, with the number of cases involved, it was possible to exclude a relative risk of 1.4 for long-term use or for ever use before first birth.

Use of oral contraceptives and risk of invasive cervical cancer in previously screened women

Within the context of a larger hospital-based case-control study carried out to assess the efficacy of cervical cancer screening, the possible association between oral contraceptives and risk of invasive cervical cancer has been studied as well. Because in the GDR cytological screening is an integral part of the gynaecological basic care, only a few women reported oral contraceptive use but had no Pap-smears in that study. Thus, the analysis was confined to those 129 cases and 275 controls who had at least one screening Pap-smear in their history and were below the age 55. The significantly increased relative risks for users decreased after adjustment for factors of sexual behaviour and interval since last Pap-smear but remained statistically significant or at borderline significance for some categories of usage. This concerns, in particular, long-term use (7+ years) and early onset of use (less than or equal to 24 years) with relative risks of 1.8 and 3.0, respectively.

Menopausal oestrogens and breast cancer risk: an expanded case-control study

A study among 1960 post-menopausal breast cancer cases and 2258 controls identified through a nation-wide screening program enabled evaluation of effects of oestrogen use on breast cancer risk. Ever use was not associated with increased risk (RR = 1.0), but a significant trend was observed with increasing years of use, with users of 20 or more years being at a 50% excess risk. Elevations associated with long-term use were apparent across all menopause subgroups (natural, ovaries retained, ovaries removed). Hormones exerted particularly adverse effects in those initiating use subsequent to a diagnosis of benign breast disease, particularly long-term users (RR = 3.0, 95% CI 1.6-5.5). There was also some indication that effects predominated among the lower stage tumours, an observation similar to that observed for endometrial cancer. These findings support a role for oestrogens in the aetiology of breast cancer, although risk appears to be enhanced only after extended periods of use, and not to the extent observed for other hormonally-sensitive tumours.

Long-term use of oral contraceptives and cervical neoplasia: an association confounded by other risk factors?

One-hundred-and-forty women with cervical intraepithelial neoplasia (CIN) found during pregnancy were compared to 280 pregnant age-matched controls. Information was obtained on obstetrical and gynecological history, sexual behaviour, contraceptive use and smoking of the female and of the male partner. Oral contraceptive use for 60 months or more was significantly associated with CIN. This significance vanished when the effect of confounding factors was controlled for in a log-linear analysis. According to these results, long-term oral contraceptive use does not seem to be a causal factor of CIN, but these women constitute a high risk group due to sexual history and smoking habits and should thus be referred for a regular cytological screening.

Hospitalizations among black women using contraceptives

We analyzed hospitalizations among 26,507 young black women who attended a large metropolitan family planning clinic between 1968 and 1976. Age-adjusted hospitalization rates were compared for women using oral contraceptives, intrauterine contraceptive devices, and depot medroxyprogesterone acetate. Overall, intrauterine contraceptive device and depot medroxyprogesterone acetate users were hospitalized at about the same rate, while women using oral contraceptives were hospitalized 30% less often. The oral contraceptive users were not hospitalized at a higher rate for circulatory disease. Compared to women using intrauterine contraceptive devices, users of oral contraceptives and depot medroxyprogesterone acetate were less likely to be hospitalized for benign breast disease (rate ratios = 0.5 and 0.2, respectively, with 95% confidence limits of 0.3 to 0.7 and 0.1 to 0.5) and for pelvic inflammatory disease. Women were four times as likely to be using depot medroxyprogesterone acetate when they were hospitalized with carcinoma in situ of the cervix, but depot medroxyprogesterone acetate users with at least 3 years of use were less likely to be hospitalized for carcinoma in situ than comparable groups of oral contraceptive and intrauterine contraceptive device users.

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.

Invasive cervical cancer and combined oral contraceptives. WHO collaborative study of neoplasia and steroid contraceptives

A multicentre, hospital based case-control study is being conducted under the auspices of the World Health Organisation to determine whether steroid contraceptives alter the risk of gynaecological, breast, and hepatic neoplasms. Preliminary results, largely from developing countries, on the relation between combined oral contraceptives and invasive cervical carcinoma showed a relative risk of 1.19 (95% confidence interval 0.99-1.44) in women who had ever used oral contraceptives. The risk increased with duration of use, giving a relative risk of 1.53 after five years. This finding supports a causal interpretation, but it could also be due to incomplete control for confounding sexual variables and other sources of bias.

Characteristics of respondents and non-respondents to a mailed questionnaire

In establishing a cohort of U.S. nurses, an assessment of response bias was made comparing respondents and non-respondents with regard to age, education, state of residence, employment status, field of employment, and major specialty. Overall, the 122,328 respondents (69.7 per cent) and 43,222 non-respondents were quite similar. Together with the reasonable response rate in a homogeneous population, this suggests that estimation of exposure-disease associations is unlikely to be affected by major bias due to non-response.

Interpretation of data by the clinician

The cardinal challenges to every practicing physician are to interpret clinical data correctly and to place them in proper perspective. Clinical investigations frequently lack the rigidly controlled conditions and the careful experimental designs usually found in preclinical animal studies, and this deficiency is partially attributable to the inherent complexities of clinical medicine. Consequently, a great deal of controversy results from conflicting interpretations, extrapolations and overextension of limited data that are often equivocal. More careful appraisal of data and increased awareness of the well-known pitfalls found in retrospective and prospective studies, in which biostatistical design and clinical relevance are often incompatible, are emphasized, and personal biases and the flagrant sensationalism expounded by the media are condemned. The clinician is cautioned to sift through the data, consider the benefit/risk ratio for each patient and then to subordinate the role of critical scientist and assume the role of physician, exercising good judgment in light of the existing evidence and the immediate problems at hand.

Oral contraceptives and breast disease in premenopausal Northern Albertan women

The results of a prospective study on oral contraceptive use and breast disease in northern Alberta are presented. The study groups comprised all women aged 30 to 49 examined in diagnostic breast clinics at the Cross Cancer Institute between 1971 and 1974. Three hundred and one patients had breast cancer, 692 had a subsequent biopsy for a benign breast condition, and 548 had no subsequent biopsy. A tendency for an increased relative risk (RR) of breast cancer in women taking oral contraceptives for periods of 1 to 5 years was evident, with relative risk decreased or unaffected in users of less than 12 months (RR = 0.6) or more than 5 years (RR = 1.0). A slightly increased risk was apparent in patients using oral contraceptives within a year prior to attendance at the clinic (recent users); this increase was emphasized when recent users with a prior biopsy for benign breast disease were analyzed alone (RR = 5.0). In women with a prior breast biopsy, use of oral contraceptives for more than 5 years increased risk of breast cancer nine-fold. Former users who had taken oral contraceptives for less than a year showed a significant reduction in breast cancer risk (RR = 0.3). The risk of benign breast disease was also reduced in former users (RR = 0.6) as well as in long-term users (RR = 0.5).

Oral contraceptives and birth defects

We reviewed the birth certificates and hospital records of 7723 infants those mothers had reported using oral contraceptives. The overall frequency of malformation was 4.3 per cent for infants whose mothers terminated use of oral contraceptives shortly before conception, as compared with 3.3 per cent for infants whose mothers did not take oral conceptives diring the three years before conception. The 90 per cent confidence limits for the prevalence ratio were 1.0 and 1.7. No difference was apparent for major malformations. For specific malformations the most notable difference was for undescented testis, but this excess, like the overall excess, could be explained by sampling variability. Despite the slightly greater rate of minor malformations in the short-interval group, a reasonable interpretation of these data would be that oral contraceptives present no major teratogenic hazard.