The differential risk of oral contraceptives: the impact of full exposure history

A test for the correct specification of marginal structural models

Marginal structural models (MSMs) allow estimating the causal effect of a time-varying exposure on an outcome in the presence of time-dependent confounding. The parameters of MSMs can be estimated utilizing an inverse probability of treatment weight estimator under certain assumptions. One of these assumptions is that the proposed causal model relating the outcome to exposure history is correctly specified. However, in practice, the true model is unknown. We propose a test that employs the observed data to attempt validating the assumption that the model is correctly specified. The performance of the proposed test is investigated with a simulation study. We illustrate our approach by estimating the effect of repeated exposure to psychosocial stressors at work on ambulatory blood pressure in a large cohort of white-collar workers in Québec City, Canada. Code examples in SAS and R are provided to facilitate the implementation of the test.

The association between new generation oral contraceptive pill and the development of inflammatory bowel diseases

Background/Aims

To examine the association between use of oral contraceptive pills (OCPs) and the risk of developing inflammatory bowel diseases (IBD), in a modern cohort.

Methods

A prospective nested case-control study across sites in the Asia-Pacific region was conducted; involving female IBD cases and asymptomatic controls. Subjects completed a questionnaire addressing questions related to OCP use. Primary outcome was the risk of development of IBD of those exposed to OCP versus non-exposure. Secondary outcomes were development of Crohn's disease (CD) versus ulcerative colitis (UC), and whether age of first use of OCP use may be associated with risk of IBD.

Results

Three hundred and forty-eight female IBD cases (41% CD, median age: 43 years) and 590 female age-matched controls were recruited. No significant association was found between OCP use and the risk of IBD (odds ratio [OR], 1.65; 95% confidence interval, 0.77-3.13; P=0.22), CD (OR, 1.55) or UC (OR, 1.01). The lack of association persisted when results were adjusted for age and smoking. IBD cases commenced OCP use at a younger age than controls (18 years vs. 20 years, P=0.049).

Conclusions

In this large cohort of subjects from the Asia-Pacific region, we found a modest but not significantly increased risk of developing IBD amongst OCP users.

Drospirenone-Containing Oral Contraceptive Pills and the Risk of Venous Thromboembolism: An Assessment of Risk in First-Time Users and Restarters

INTRODUCTION

The effects of drospirenone-containing combined oral contraceptives (COCs) on the risk of venous thromboembolism (VTE) remain controversial due to the challenge in distinguishing between first-time users and restarters, and their different underlying VTE risks, in healthcare databases.

OBJECTIVES

The aim of this study was to describe the challenge of studying the risk of VTE among first-time users of drospirenone-containing COCs in a healthcare database and assess the risk among first-time users and restarters.

METHODS

We used data from the Clinical Practice Research Datalink to construct two cohorts. The first-time user cohort included all women aged 16-45 years who received a first ever prescription of drospirenone- or levonorgestrel-containing COCs between May 2002 and March 2015. The restarter cohort included those who were restarting a COC after a period of non-use of ≥6 months. Cox proportional hazards models adjusted for high dimensional propensity scores were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

The final cohorts included 55,139 first-time users (3582 drospirenone and 51,557 levonorgestrel) and 162,959 restarters (23,191 drospirenone and 139,768 levonorgestrel). The adjusted HR of VTE associated with drospirenone versus levonorgestrel was 3.19 (95% CI 1.12-9.08) for first-time users and 1.96 (95% CI 1.12-3.41) for restarters.

CONCLUSIONS

We found an elevated risk of VTE associated with drospirenone-containing COCs in comparison with levonorgestrel-containing COCs in both cohorts. While left truncation of healthcare databases is a concern for the identification of first-time users, the use of a more explicit cohort of restarters suggests a doubling of VTE risk with drospirenone-containing COCs.

Combined hormonal contraception and the risk of venous thromboembolism: a guideline

While venous thromboembolism (VTE) is rare in young women of reproductive age, combined oral contraceptives increase the risk of VTE. In the patient in whom combined hormonal contraception is appropriate, it is reasonable to use any currently available preparation.

Family history of venous thromboembolism is a risk factor for venous thromboembolism in combined oral contraceptive users: a nationwide case-control study

BACKGROUND

The aim was to assess the risk of venous thromboembolism (VTE) associated with use of combined oral contraceptives (COCs) in women with a family history of VTE.

METHODS

The study is a Swedish nationwide case-control study based on the Multigeneration register, the Swedish Hospital Discharge Register, the Outpatient Care Register, and the Swedish Prescribed Drug Register. Cases (n = 2,311) were non-pregnant Swedish women aged 15-49 with first VTE diagnoses between January 2006 and December 2010. Five controls without VTE were matched to each case on age and education level. Conditional logistic regression examined the associations with VTE with determination of odds ratio (OR) for first VTE diagnosis. Effect modification was assessed by interaction testing.

RESULTS

Both among controls (14.6 % vs. 4.5 %; p < 0.0001) and cases (27.2 % vs. 8.8 %; p < 0.0001) COC use was more common in women without a family history of VTE compared with women with a family history of VTE. In a multivariate conditional logistic regression model the OR for VTE was 2.53 (95 % CI 2.23-2.87) for COC users and 2.38 (2.09-2.71) for individuals with a family history of VTE. The OR for VTE for COC users with a family history of VTE was 6.02 (5.02-7.22). There was no significant interaction between family history of VTE and COC use (OR 0.92, 0.57-1.46).

CONCLUSIONS

Family history of VTE is a risk factor for VTE in women using COCs. The low prevalence of COC use among women with a family history of VTE suggests that family history of VTE is considered when COCs are prescribed in Sweden. The present study may therefore even underestimate the importance of family history of VTE. The lack of interaction indicates that the risk of COC use in women with family history of VTE is determined by the product of the ORs for family history and COC use.

Hormonal contraception, thrombosis and age

INTRODUCTION

This paper reviews the risk of thrombosis with use of different types of hormonal contraception in women of different ages.

AREAS COVERED

Combined hormonal contraceptives with desogestrel, gestodene, drospirenone or cyproterone acetate (high-risk products) confer a sixfold increased risk of venous thromboembolism as compared with nonusers, and about twice the risk as compared with users of products with norethisterone, levonorgestrel or norgestimate (low-risk products). Transdermal patches and vaginal ring belong to high-risk products. The risk of thrombotic stroke and myocardial infarction is increased 50 - 100% with use of combined products, with little difference in risk between different progestins. Progestin-only products do not confer any increased risk of venous or arterial thrombosis, except for progestin depot, which may double the risk of venous thrombosis.

EXPERT OPINION

First choice in women below 35 years should be a combined low-risk pill, that is, with a second-generation progestin, with the lowest compliable dose of estrogen. Young women with risk factors of thrombosis such as age above 35 years, genetic predispositions, adiposity, polycystic ovary syndrome, diabetes, smoking, hypertension or migraine with aura should not use high-risk products, but should primarily consider progestin-only products, and be careful to use low-risk combined products.

Use of combined oral contraceptives and risk of venous thromboembolism: nested case-control studies using the QResearch and CPRD databases

OBJECTIVE

To investigate the association between use of combined oral contraceptives and risk of venous thromboembolism, taking the type of progestogen into account.

DESIGN

Two nested case-control studies.

SETTING

General practices in the United Kingdom contributing to the Clinical Practice Research Datalink (CPRD; 618 practices) and QResearch primary care database (722 practices).

PARTICIPANTS

Women aged 15-49 years with a first diagnosis of venous thromboembolism in 2001-13, each matched with up to five controls by age, practice, and calendar year.

MAIN OUTCOME MEASURES

Odds ratios for incident venous thromboembolism and use of combined oral contraceptives in the previous year, adjusted for smoking status, alcohol consumption, ethnic group, body mass index, comorbidities, and other contraceptive drugs. Results were combined across the two datasets.

RESULTS

5062 cases of venous thromboembolism from CPRD and 5500 from QResearch were analysed. Current exposure to any combined oral contraceptive was associated with an increased risk of venous thromboembolism (adjusted odds ratio 2.97, 95% confidence interval 2.78 to 3.17) compared with no exposure in the previous year. Corresponding risks associated with current exposure to desogestrel (4.28, 3.66 to 5.01), gestodene (3.64, 3.00 to 4.43), drospirenone (4.12, 3.43 to 4.96), and cyproterone (4.27, 3.57 to 5.11) were significantly higher than those for second generation contraceptives levonorgestrel (2.38, 2.18 to 2.59) and norethisterone (2.56, 2.15 to 3.06), and for norgestimate (2.53, 2.17 to 2.96). The number of extra cases of venous thromboembolism per year per 10,000 treated women was lowest for levonorgestrel (6, 95% confidence interval 5 to 7) and norgestimate (6, 5 to 8), and highest for desogestrel (14, 11 to 17) and cyproterone (14, 11 to 17).

CONCLUSIONS

In these population based, case-control studies using two large primary care databases, risks of venous thromboembolism associated with combined oral contraceptives were, with the exception of norgestimate, higher for newer drug preparations than for second generation drugs.

Trends and patterns of hormonal contraceptive prescribing for adolescents in primary care in the U.K

BACKGROUND

Hormonal contraceptives are the most common method used worldwide by teenagers to prevent unwanted pregnancies. To date there are limited data about such use by teenagers in the UK. This study investigated trends and patterns of hormonal contraceptive prescribing to adolescents aged 12-18 years in UK primary care between 2002 and 2011.

METHODS

A retrospective cohort study using the IMS Disease Analyzer database was conducted. All females aged 12-18 years with ≥1 prescription for a contraceptive drug between 1 January 2002 and 31 December 2011 were included. Annual prevalence of contraceptive drug prescribing was calculated, and indications for prescribing, and types of contraceptive drug prescribed, were examined.

RESULTS

In 2002, 13.7% (6135/44 532) of female adolescents received prescriptions for hormonal contraceptives, compared to 19.0% (6597/34 676) in 2011. The majority of female adolescents [2002: 76.2% (4676/6135); 2011: 65.7% (4334/6597)] received a contraceptive drug for 'contraceptive management'. The combined oral contraceptive (COC), 'progestogen+estrogen', was the most commonly prescribed. Although use of progestogen-only contraceptives was lower than COCs, the number of patients who received desogestrel pills and etonogestrel implants increased during the study period; levonorgestrel pill use declined. Only one injectable progestogen, long-acting depot medroxyprogesterone acetate, was prescribed.

CONCLUSIONS

Use of hormonal contraceptives among adolescents increased between 2002 and 2011, and COC usage was dominant. The increasing use of hormonal contraceptives in adolescents, especially in younger adolescents, warrants further investigation, including research into the long-term safety of these medicines in this age group.

Combined oral contraceptives: venous thrombosis

BACKGROUND

Combined oral contraceptive (COC) use has been associated with venous thrombosis (VT) (i.e., deep venous thrombosis and pulmonary embolism). The VT risk has been evaluated for many estrogen doses and progestagen types contained in COC but no comprehensive comparison involving commonly used COC is available.

OBJECTIVES

To provide a comprehensive overview of the risk of venous thrombosis in women using different combined oral contraceptives.

SEARCH METHODS

Electronic databases (Pubmed, Embase, Web of Science, Cochrane, CINAHL, Academic Search Premier and ScienceDirect) were searched in 22 April 2013 for eligible studies, without language restrictions.

SELECTION CRITERIA

We selected studies including healthy women taking COC with VT as outcome.

DATA COLLECTION AND ANALYSIS

The primary outcome of interest was a fatal or non-fatal first event of venous thrombosis with the main focus on deep venous thrombosis or pulmonary embolism. Publications with at least 10 events in total were eligible. The network meta-analysis was performed using an extension of frequentist random effects models for mixed multiple treatment comparisons. Unadjusted relative risks with 95% confidence intervals were reported.Two independent reviewers extracted data from selected studies.

MAIN RESULTS

3110 publications were retrieved through a search strategy; 25 publications reporting on 26 studies were included. Incidence of venous thrombosis in non-users from two included cohorts was 0.19 and 0.37 per 1 000 person years, in line with previously reported incidences of 0,16 per 1 000 person years. Use of combined oral contraceptives increased the risk of venous thrombosis compared with non-use (relative risk 3.5, 95% confidence interval 2.9 to 4.3). The relative risk of venous thrombosis for combined oral contraceptives with 30-35 μg ethinylestradiol and gestodene, desogestrel, cyproterone acetate, or drospirenone were similar and about 50-80% higher than for combined oral contraceptives with levonorgestrel. A dose related effect of ethinylestradiol was observed for gestodene, desogestrel, and levonorgestrel, with higher doses being associated with higher thrombosis risk.

AUTHORS' CONCLUSIONS

All combined oral contraceptives investigated in this analysis were associated with an increased risk of venous thrombosis. The effect size depended both on the progestogen used and the dose of ethinylestradiol. Risk of venous thrombosis for combined oral contraceptives with 30-35 μg ethinylestradiol and gestodene, desogestrel, cyproterone acetate and drospirenone were similar, and about 50-80% higher than with levonorgestrel. The combined oral contraceptive with the lowest possible dose of ethinylestradiol and good compliance should be prescribed-that is, 30 μg ethinylestradiol with levonorgestrel.

Hormonal contraceptives and venous thromboembolism: an epidemiological update

Since the early 1960s, it has been well documented that combined hormonal contraceptives increase the risk of cardiovascular disease. Newer generation of oral formulations, as well as non-oral contraceptives (transdermal and vaginal), have been recently studied for thrombotic risk. This review provides a summary of the association between hormonal contraceptives and venous thromboembolism with emphasis on new formulations of hormonal contraceptives as well as route of administration. A systematic search of Medline database was done for all relevant articles which included women having used third generation pills, and the development of new progestins. Eligible articles published in English and reporting the risk of venous thromboembolism (VTE) (pulmonary embolism or deep venous thrombosis) among users of hormonal contraceptives were reviewed. A quantitative assessment was made from included studies. Current use of drospirenone or cyproterone oral combined contraceptives increased the risk of VTE compared with second generation pills (pooled OR: 1.7; 95% confidence interval [95% CI]: 1.4-2.2 and OR: 1.8; 95% CI: 1.4-2.3, respectively). In the context of contraceptive use, non-oral route of ethinyl-estradiol administration seems to be more thrombogenic than oral route. In contrast, low doses of both oral progestin contraceptives and intrauterine levonorgestrel could be safe with respect to VTE risk. In conclusion, newer generation formulations of hormonal contraceptives, as well as the non-oral hormonal contraceptive, seem to be more thrombogenic than second generation hormonal contraceptives.

A pathway to improved prospective observational post-authorization safety studies

Randomized controlled trials (RCTs) are the gold standard for assessing the efficacy of drugs but not necessarily so for drug safety where inadequate power to detect either multiple or rare adverse events is a major handicap. Furthermore, the conditions under which drugs are approved for market use are often different from the settings in actual use. Indeed, with their control mechanisms, trials are by design largely inadequate for the identification of potential safety signals, especially of the rare type, hence the value of postmarketing surveillance and risk management plan-based activities. Today, clinical trials constitute only a part of the research that goes into assessing the safety of drugs. Observational studies, where the investigators merely collect data on treatments received by patients and their health status in routine clinical practice are increasing in uptake because they reflect the real-life utility of drugs, despite the absence of random treatment assignment. Although such studies generally provide less compelling evidence than RCTs, they can be far more useful to drug safety assessment activities than generally acknowledged. An increasing number of post-authorization safety studies (PASS) within the European Medicines Agency's jurisdiction are of the observational type - considered perhaps as more appropriate vehicles for exploring and documenting how products perform in the real world. A similar trend is emerging in the US following the FDA Amendments Act of 2007; since early 2010, an increasing number of post-approval commitments mandated by the FDA include observational studies. However, despite this pattern, not much is known about ongoing efforts to address many of the recognized inadequacies associated with existing methodologies and practices currently adopted in observational PASS. This current opinion presents an overview of some of the main challenges we face in prospective observational PASS, mainly from practical experience, and proposes certain steps for improvement.

Venous thrombosis and oral contraceptives: current status

The use of oral contraceptives is associated with an increased risk of venous thrombosis. It is now generally accepted that women who use oral contraceptives that contain so-called third-generation progestins (desogestrel or gestodene) are exposed to a twofold higher risk of venous thrombosis than women who use oral contraceptives that contain the second-generation progestin levonorgestrel. Coagulation studies demonstrated that oral contraceptives increase the plasma level of prothrombin, decrease the level of protein S and induce acquired activated protein C resistance. The changes in hemostatic parameters can explain why women who use oral contraceptives are exposed to an increased risk of venous thrombosis and why the risk is further increased in third-generation oral contraceptive users.

Hormonal contraception and venous thromboembolism

BACKGROUND

New studies about the influence of hormonal contraception on the risk of venous thromboembolism (VTE) have been published.

AIM

To evaluate new epidemiological data and to propose clinical consequences.

DESIGN

A literature survey.

METHODS

Studies assessing the risk of specific types of hormonal contraception were evaluated, compared and set into a clinical perspective.

RESULTS

The majority of newer studies have demonstrated a threefold increased risk of VTE in current users of medium- and low-dose combined oral contraceptives (COCs) with norethisterone, levonorgestrel (LNG) or norgestimate compared with non-users. The same studies have demonstrated a sixfold increased risk of VTE in users of combined pills with desogestrel, gestodene, drospirenone or cyproteroneacetate, and in users of the contraceptive vaginal ring, compared with non-users. The rate ratio of VTE between users of COCs with newer progestogens compared with users of COCs with LNG was 1.5-2.8 in seven studies and 1.0 in two studies. Progestogen-only contraception did not confer an increased risk of VTE in any study. The incidence rate of VTE in non-pregnant women aged 15-49 years using non-hormonal contraception is three per 10 000 years.

CONCLUSIONS

For women starting on hormonal contraception, we recommend medium- or low-dose combined pills with norethisterone, LNG or norgestimate as first-choice preparations. For the many women who are users of COCs with newer progestogens, although the absolute risk of VTE is low, a change to combined pills with norethisterone, LNG or norgestimate may halve their risk of VTE. Finally, we recommend COCs with 20 μg estrogen combined with the older progestogens to be launched in the Scandinavian countries. Women at an increased risk of VTE should consider progestogen-only contraception or non-hormonal contraception.

Oral contraceptives and venous thromboembolism: a systematic review and meta-analysis

BACKGROUND

An association between oral contraceptive (OC) use and venous thromboembolism (VTE) has long been recognized. However, no summary estimates of the increase in VTE risk associated with OC use have been available since 1995, and no meta-analyses have evaluated the VTE risk of new preparations containing drospirenone.

OBJECTIVE

The aim of the study was to carry out a meta-analysis to summarize existing evidence on the association between venous VTE and OC use, and to investigate how such an association may vary according to the type of OC, OC user characteristics, study characteristics and biases.

METHODS

Relevant cohort or case-control studies were searched in MEDLINE and other electronic databases up to May 2010, with no language restriction. Data were combined using a generic inverse-variance approach. Meta-regression in addition to stratification was used to explore potential predictors of the summary estimate of risk.

RESULTS

Sixteen cohort and 39 case-control studies were included in at least one comparison. Overall, the odds ratio (OR) of OC users versus non-users was 3.41 (95% CI 2.98, 3.92). This estimate was based upon nine cohort studies evaluating approximately 12 000 000 person-years, and 23 case-control studies including approximately 45 000 women. VTE risk for OC users was significantly lower in studies evaluating 'all VTE cases' than in those evaluating 'idiopathic VTE only' (OR 3.09 and 4.94, respectively). Among the carriers of genetic mutations G20210A and Factor V Leiden (FVL), OC users showed a significantly increased VTE risk compared with non-users (OR 1.63; 95% CI 1.01, 2.65, and OR 1.80; 95% CI 1.20, 2.71, respectively). When the newest OCs containing drospirenone were compared with non-drospirenone-containing OCs (except those containing levonorgestrel only), VTE risk did not significantly increase (OR 1.13; 95% CI 0.94, 1.35).

CONCLUSIONS

This meta-analysis confirms that OC use significantly increases VTE risk. The strength of this association, however, varies according to the generation of OC, type of outcome and presence of a genetic mutation, with ORs ranging from 3 to 5.

Occurrence, fate and removal of synthetic oral contraceptives (SOCs) in the natural environment: a review

Synthetic oral contraceptives (SOCs) are a group of compounds with progestagenic and/or androgenic activities, with some also possessing estrogenic activities. Recent research has documented that some of these emerging contaminants have adverse effects on aquatic organisms at very low concentrations. To facilitate the evaluation of their latent risks, published works on their occurrence and fate in the environment are reviewed. Androgenic/progestagenic relative potencies or relative binding affinity of these SOCs as well as their physicochemical properties and toxicity are summarized. Appropriate analytical methods are outlined for various environmental sample types, including methods of sample preparation and limit of detection/quantification (LOD/LOQ). Finally results on their occurrence and fate in wastewater treatment plants (WWTPs) and other environments are critically examined.

Risk of venous thromboembolism from use of oral contraceptives containing different progestogens and oestrogen doses: Danish cohort study, 2001-9

OBJECTIVE

To assess the risk of venous thromboembolism from use of combined oral contraceptives according to progestogen type and oestrogen dose.

DESIGN

National historical registry based cohort study.

SETTING

Four registries in Denmark.

PARTICIPANTS

Non-pregnant Danish women aged 15-49 with no history of thrombotic disease and followed from January 2001 to December 2009.

MAIN OUTCOME MEASURES

Relative and absolute risks of first time venous thromboembolism.

RESULTS

Within 8,010,290 women years of observation, 4307 first ever venous thromboembolic events were recorded and 4246 included, among which 2847 (67%) events were confirmed as certain. Compared with non-users of hormonal contraception, the relative risk of confirmed venous thromboembolism in users of oral contraceptives containing 30-40 µg ethinylestradiol with levonorgestrel was 2.9 (95% confidence interval 2.2 to 3.8), with desogestrel was 6.6 (5.6 to 7.8), with gestodene was 6.2 (5.6 to 7.0), and with drospirenone was 6.4 (5.4 to 7.5). With users of oral contraceptives with levonorgestrel as reference and after adjusting for length of use, the rate ratio of confirmed venous thromboembolism for users of oral contraceptives with desogestrel was 2.2 (1.7 to 3.0), with gestodene was 2.1 (1.6 to 2.8), and with drospirenone was 2.1 (1.6 to 2.8). The risk of confirmed venous thromboembolism was not increased with use of progestogen only pills or hormone releasing intrauterine devices. If oral contraceptives with desogestrel, gestodene, or drospirenone are anticipated to increase the risk of venous thromboembolism sixfold and those with levonorgestrel threefold, and the absolute risk of venous thromboembolism in current users of the former group is on average 10 per 10,000 women years, then 2000 women would need to shift from using oral contraceptives with desogestrel, gestodene, or drospirenone to those with levonorgestrel to prevent one event of venous thromboembolism in one year.

CONCLUSION

After adjustment for length of use, users of oral contraceptives with desogestrel, gestodene, or drospirenone were at least at twice the risk of venous thromboembolism compared with users of oral contraceptives with levonorgestrel.

SOGC clinical practice guideline. No. 252, December 2010. Oral contraceptives and the risk of venous thromboembolism: an update

OBJECTIVE

To provide current and emerging evidence on oral contraceptives and the risk of venous thromboembolism.

EVIDENCE

Articles published in English from 2005 were retrieved through searches of PubMed and Medline, using the following terms: venous thromboembolism, VTE, contraception, oral contraceptives, hormonal contraception. Results were restricted to systematic reviews, randomized control trials/controlled clinical trials, and observational studies. Searches were updated on a regular basis and incorporated in the guideline to May 2010. Grey (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The quality of evidence was rated using the criteria described by the Canadian Task Force on Preventive Health Care (Table). SUMMARY STATEMENTS: 1. Modern oral contraceptives offer highly effective contraception and a range of non-contraceptive benefits. (I) 2. Venous thromboembolism, although rare, remains one of the serious adverse consequences of hormonal contraception. Best evidence indicates that venous thromboembolism rates in non-users of reproductive age approximate 4-5/10 000 women per year; rates in oral contraceptive users are in the range of 9-10/10 000 women per year. For comparison, venous thromboembolism rates in pregnancy approach 29/10 000 overall and may reach 300-400/10 000 in the immediate postpartum period. (II-1) 3. Research demonstrates that oral contraceptives with ≤ 35 µg of ethinyl estradiol carry a lower risk of venous thromboembolism than oral contraceptives with 50 µg. (II-2) Although preliminary data suggest a possible further reduction in venous thromboembolism with oral contraceptives with < 35 µg ethinyl estradiol, robust data to support this conclusion are presently lacking. 4. Recent contradictory evidence and the ensuing media coverage of the venous thromboembolism risk attributed to the progestin component of certain newer oral contraceptive products have led to fear and confusion about the safety of oral contraceptives in general and drospirenone-containing oral contraceptives in particular. "Pill scares" of this nature have occurred in the past, with panic stopping of the pill, increased rates of unplanned pregnancy, and no subsequent decrease in venous thromboembolism rates. (II-3) 5. Two high quality research studies that addressed the venous thromboembolism risk associated with various oral contraceptives found comparable venous thromboembolism rates with drospirenone-containing oral contraceptives and other approved products. (II-1) 6. Two reports suggesting an increased risk of venous thromboembolism with drospirenone-containing oral contraceptives have significant methodological flaws that render their conclusions suspect. It seems likely that residual confounding could have distorted both the results and the conclusions of these reports. (II-3).

Tailoring combination oral contraceptives to the individual woman

BACKGROUND

Over the last 50 years, there has been intense interest in the type of progestin used in combined oral contraceptives (COC) in an attempt to exploit novel properties and minimize adverse events. At the same time, the dose of synthetic estrogen, ethinylestradiol, in COC pills has been reduced to minimize risks for ischemic stroke, myocardial infarction, and venous thromboembolism. New formulations, including extended-cycle or continuous-use COCs or those that use a natural estrogen, estradiol, may offer improvements over their predecessors.

METHODS

A Medline search was performed to encompass studies published since 1990 that pertain to the pharmacology of estrogens and progestins used in COCs, risks and adverse events associated with COCs, and extended or continuous-use COCs.

RESULTS

New progestins structurally related to progesterone and spironolactone may exhibit more selective binding to the progesterone receptor and lack androgenic adverse effects associated with progestins structurally related to testosterone. Recently, COCs containing natural (17β-estradiol) or conjugated estrogen (estradiol valerate) rather than ethinylestradiol have been developed in order to move to a more natural estrogen. Although many of the new progestins incorporated into COCs have not demonstrated the negative effects on lipid metabolism and other adverse events associated with the traditional progestins, the goal of attaining good cycle control has yet to be achieved. Extended-cycle and continuous-use regimens are now available that reduce the frequency of menses, but breakthrough bleeding remains a problem.

CONCLUSIONS

Appropriate counseling to raise awareness of the specific characteristics of the different COC options available may optimize adherence and patient acceptability.

Estrogen-free oral hormonal contraception: benefits of the progestin-only pill

Although combined oral contraceptives (COCs) are commonly used and highly effective in preventing pregnancy, they may not be suitable for some women. COC use is associated with increased rates of cardiovascular events and is not recommended in nonbreastfeeding women in the immediate postpartum period or in breastfeeding women during the initial 6 months of breastfeeding. Moreover, estrogen-related adverse effects, such as headache, are common. Estrogen-free progestin-only pills (POPs) are a valuable option in women who prefer to take an oral hormonal contraceptive, but are ineligible for, or choose not to use, COCs. Although some POPs have been associated with lower contraceptive effectiveness than COCs, the POP containing desogestrel has shown similar contraceptive effectiveness to COCs. The most commonly reported complaints in women using all POPs are bleeding problems. Counseling women interested in using POPs about the variable bleeding patterns associated with this method may improve compliance and acceptance.

Risk of venous thromboembolism and the use of dienogest- and drospirenone-containing oral contraceptives: results from a German case-control study

OBJECTIVE

The primary objective of the study was to clarify whether the use of the oral contraceptive 2 mg dienogest/30 microg ethinylestradiol (DNG/EE) is associated with a higher risk of venous thromboembolism (VTE) than the use of other combined oral low-dose contraceptives (i.e. containing < or =30 microg EE), particularly oral contraceptives containing levonorgestrel (LNG). The secondary objective was to investigate the VTE risk associated with drospirenone/ethinylestradiol (DRSP/EE) in comparison to low-dose LNG/EE.

METHODS

This German community-based, case-control study recruited VTE cases from the primary care sector. Eligible cases were women aged 15-49 years with a VTE between January 2002 and February 2008. Four controls (women without a confirmed or potential VTE before the index date) were matched by age and region to each case. Medical information relevant for the assessment of VTE was abstracted from patient charts. Data on personal characteristics of the patients were collected via self-administered questionnaires. At the end of the study a blinded adjudication of the reported VTE was conducted. Conditional logistic regression techniques were used, adjusting for nine potential confounders, including personal history of VTE, family history of VTE, body mass index, duration of current combined oral contraceptive (COC) use and smoking.

RESULTS

A total of 680 VTE cases and 2720 corresponding controls were analysed. The mean age of cases and controls was - as a result of matching - almost identical (36.1 years). A total of 35, 25, and 60 of the cases had used DNG-, DRSP- and LNG-containing low-dose COCs, respectively, at the time of the VTE diagnosis. The crude odds ratio (OR) for VTE associated with current COC use in comparison to women who had never used a COC before the index date was 1.9 (95% CI 1.5-2.5), the adjusted OR was 2.3 (95% CI 1.7-3.0). The point estimate of the crude OR of DNG/EE vs any other low-dose COCs was 0.9 (95% CI 0.6-1.3), the adjusted OR was 0.9 (95% CI 0.6-1.4). The crude ORs for DNG/EE and DRSP/EE vs low-dose LNG/EE were 1.1 (95% CI 0.7-1.8) and 1.0 (95% CI 0.6-1.6), respectively; the adjusted ORs were 1.1 (95% CI 0.7-1.9) and 1.0 (95% CI 0.6-1.8).

CONCLUSIONS

The study confirms that COC use is associated with an increased risk of VTE. The VTE ORs (adjusted and crude) that compared DNG/EE and DRSP/EE with other low-dose COCs (including LNG/EE) were close to unity and do not indicate a higher risk for users of DNG/EE or DRSP/EE.

Use of oral contraceptives containing gestodene and risk of venous thromboembolism: outlook 10 years after the third-generation "pill scare"

BACKGROUND

This study investigated whether gestodene-containing oral contraceptives (OCs) carry a higher risk of venous thromboembolism (VTE) than OCs containing progestins other than desogestrel and gestodene. The study was conducted based on the hypothesis that the biases and confounding factors that were present initially after the introduction of new so-called "third-generation" OCs (i.e., those containing desogestrel and gestodene) in the 1990s, which likely contributed to the alleged increased risk of VTE, may have vanished after 10 years.

STUDY DESIGN

This was a matched case-control study using data identified for women (aged 15-49 years) with suspected or diagnosed VTE (deep vein thrombosis or pulmonary embolism) that occurred between January 2002 and February 2006 in Austria. All VTE cases were validated by an attending/relevant physician(s), a detailed review of medical records and patient-completed questionnaires. Data were analyzed using an unconditional logistic regression model with adjustment for relevant confounders.

RESULTS

Overall, 451 VTE cases and 1,920 controls without VTE were identified. The adjusted odds ratios for confirmed VTE with OC use versus nonuse were: 3.39 (95% CI 2.36-4.87) for OCs containing gestodene and 3.14 (2.1-4.47) for OCs containing progestins other than desogestrel and gestodene. Adjusted odds ratios for a head-to-head comparison of OCs containing gestodene versus OCs containing progestins other than desogestrel and gestodene were: 0.99 (0.68-1.45) for all cases; 1.01 (0.69-1.47) for confirmed cases and 1.11 (0.73-1.69) for confirmed and idiopathic VTE cases, respectively.

CONCLUSION

The risk of VTE is not elevated in users of gestodene-containing OCs relative to users of OCs containing progestins other than desogestrel and gestodene. Our study supports the view that (i) the majority of previous results may be explained by differences in the user populations of so-called "third-generation" OCs (containing desogestrel and gestodene) and "second-generation" OCs (containing progestins other than desogestrel and gestodene) that were present shortly after market introduction of gestodene-containing OCs and that (ii) these differences seem to have disappeared over time.

International Active Surveillance Study of Women Taking Oral Contraceptives (INAS-OC Study)

Background

A 24-day regimen of contraceptive doses of drospirenone and ethinylestradiol (DRSP/EE 24d) was recently launched. This regimen has properties which may be beneficial for certain user populations (e.g., women suffering from premenstrual dysphoric disorder or acne). However, it is unknown whether this extended regimen has an impact on the cardiovascular risk associated with the use of oral contraceptives (OCs). The INternational Active Surveillance study of women taking Oral Contraceptives (INAS-OC) is designed to investigate the short- and long-term safety of the new regimen in a population which is representative for the typical user of oral contraceptives.

Methods/Design

A large, prospective, controlled, non-interventional, long-term cohort study with active surveillance of the study participants has been chosen to ensure reliable and valid results. More than 2,000 gynecologists in the US and 5 European countries (Austria, Germany, Italy, Poland, and Sweden) will recruit more than 80,000 OC users. The two to five year follow-up of these women will result in at least 220,000 documented women-years.

The main clinical outcomes of interest for the follow-up are deep venous thrombosis, pulmonary embolism, acute myocardial infarction and cerebrovascular accidents. Secondary objectives are general safety, effectiveness and drug utilization pattern of DRSP/EE 24d, return to fertility after stop of OC use, as well as the baseline risk for users of individual OC formulations.

Because of the non-interference character of this study, potential participants (first-time users or switchers) are informed about the study only after the decision regarding prescription of a new OC. There are no specific medical inclusion or exclusion criteria. Study participation is voluntary and a written informed consent is required. After the baseline questionnaire, follow-up questionnaires will be mailed to the participants every 6 months for up to 5 years after baseline. Self-reported serious adverse events will be validated by contacting the relevant physician and by reviewing relevant source documents. At the end of the study an independent blinded adjudication of relevant clinical outcomes will be conducted.

Meanwhile, this study has received ethical approval from the Western Institutional Review Board (USA) and the Medical Association in Berlin (Germany).

Discussion

The feasibility of the study is considered to be very high because of its similar design to the EURAS-OC study. All relevant methodological and logistical features of the study were successfully tested in the EURAS study.

The chosen design minimizes the impact of referral and misclassification bias, healthy user effect and loss to follow-up. Overall, it is expected that the study design is robust enough to interpret hazard ratios of 1.5 or higher.

Hormonal contraception and risk of venous thromboembolism: national follow-up study

OBJECTIVE

To assess the risk of venous thrombosis in current users of different types of hormonal contraception, focusing on regimen, oestrogen dose, type of progestogen, and route of administration.

DESIGN

National cohort study.

SETTING

Denmark, 1995-2005.

PARTICIPANTS

Danish women aged 15-49 with no history of cardiovascular or malignant disease.

MAIN OUTCOME MEASURES

Adjusted rate ratios for all first time deep venous thrombosis, portal thrombosis, thrombosis of caval vein, thrombosis of renal vein, unspecified deep vein thrombosis, and pulmonary embolism during the study period.

RESULTS

10.4 million woman years were recorded, 3.3 million woman years in receipt of oral contraceptives. In total, 4213 venous thrombotic events were observed, 2045 in current users of oral contraceptives. The overall absolute risk of venous thrombosis per 10 000 woman years in non-users of oral contraceptives was 3.01 and in current users was 6.29. Compared with non-users of combined oral contraceptives the rate ratio of venous thrombembolism in current users decreased with duration of use (<1 year 4.17, 95% confidence interval 3.73 to 4.66, 1-4 years 2.98, 2.73 to 3.26, and >4 years 2.76, 2.53 to 3.02; P<0.001) and with decreasing dose of oestrogen. Compared with oral contraceptives containing levonorgestrel and with the same dose of oestrogen and length of use, the rate ratio for oral contraceptives with norethisterone was 0.98 (0.71 to 1.37), with norgestimate 1.19 (0.96 to 1.47), with desogestrel 1.82 (1.49 to 2.22), with gestodene 1.86 (1.59 to 2.18), with drospirenone 1.64 (1.27 to 2.10), and with cyproterone 1.88 (1.47 to 2.42). Compared with non-users of oral contraceptives, the rate ratio for venous thromboembolism in users of progestogen only oral contraceptives with levonorgestrel or norethisterone was 0.59 (0.33 to 1.03) or with 75 mug desogestrel was 1.12 (0.36 to 3.49), and for hormone releasing intrauterine devices was 0.90 (0.64 to 1.26).

CONCLUSION

The risk of venous thrombosis in current users of combined oral contraceptives decreases with duration of use and decreasing oestrogen dose. For the same dose of oestrogen and the same length of use, oral contraceptives with desogestrel, gestodene, or drospirenone were associated with a significantly higher risk of venous thrombosis than oral contraceptives with levonorgestrel. Progestogen only pills and hormone releasing intrauterine devices were not associated with any increased risk of venous thrombosis.

The safety of a drospirenone-containing oral contraceptive: final results from the European Active Surveillance study on Oral Contraceptives based on 142,475 women-years of observation

OBJECTIVES

The study was conducted to compare risks of adverse cardiovascular and other events associated with the use of drospirenone (DRSP)-containing oral contraceptives (OCs) and other OCs.

METHODS AND MATERIALS

The European Active Surveillance study (EURAS) was a multinational, prospective, noninterventional cohort study of new users of DRSP, levonorgestrel (LNG) and other progestin-containing OCs. Semiannual follow-up was based on mailed questionnaires, with additional follow-up procedures when needed.

RESULTS

Overall, 58,674 women were followed for 142,475 women-years of observation. Loss to follow-up was 2.4%. Serious adverse and fatal events were rare, and rate ratios were close to unity (1.0). Cox regression analysis of cardiovascular outcomes yielded hazard ratios for DRSP-containing vs. LNG-containing and other OCs of 1.0 and 0.8 (upper 95% confidence limits, 1.8 and 1.3) for venous, and 0.3 and 0.3 (upper 95% confidence limits, 1.2 and 1.5) for arterial thromboembolism, respectively.

CONCLUSIONS

Risks of adverse cardiovascular and other serious events in users of a DRSP-containing OC are similar to those associated with the use of other OCs.

The problems with some epidemiological studies

Epidemiological studies provide a valuable tool for the investigation of the causes of disease. However, such studies alone are rarely able to prove cause. No study is perfect and the evaluation of results must take account of the design and execution of the study together with the analytic methods used. Before imputing cause it is important to consider the findings against the criteria set out by Bradford Hill. Some of the problems with studies are discussed including the specification of the data collected, accuracy of information, end point definition, study size and the way results are presented. The issues are illustrated by reference to published papers. It is concluded that unless studies are evaluated and interpreted with care they may result in more harm than good.

Modeling cumulative dose and exposure duration provided insights regarding the associations between benzodiazepines and injuries

BACKGROUND AND OBJECTIVES

Accurate assessment of medication impact requires modeling cumulative effects of exposure duration and dose; however, postmarketing studies usually represent medication exposure by baseline or current use only. We propose new methods for modeling various aspects of medication use history and employment of them to assess the adverse effects of selected benzodiazepines.

STUDY DESIGN AND SETTING

Time-dependent measures of cumulative dose or duration of use, with weighting of past exposures by recency, were proposed. These measures were then included in alternative versions of the multivariable Cox model to analyze the risk of fall related injuries among the elderly new users of three benzodiazepines (nitrazepam, temazepam, and flurazepam) in Quebec. Akaike's information criterion (AIC) was used to select the most predictive model for a given benzodiazepine.

RESULTS

The best-fitting model included a combination of cumulative duration and current dose for temazepam, and cumulative dose for flurazepam and nitrazepam, with different weighting functions. The window of clinically relevant exposure was shorter for flurazepam than for the two other products.

CONCLUSION

Careful modeling of the medication exposure history may enhance our understanding of the mechanisms underlying their adverse effects.

Hormonal contraception in women with diabetes mellitus: special considerations

Contraception is an important issue for women with diabetes mellitus as unplanned pregnancy can present major maternal and perinatal complications. The rising incidence of diabetes worldwide means increasing thought needs to be given to contraceptive options for these women. This article reviews current evidence and recommends best practice for prescribing hormonal contraceptives in women with diabetes. Women with diabetes have the same choice of contraceptives as the general population, but the potential metabolic effects of hormonal methods need to be considered in relation to an individual's diabetic profile and their need for effective contraception. Currently, there appear to be wide variations in the way that professionals evaluate the risk-benefit equation, and significant differences in prescribing practice have been identified. The World Health Organization (WHO) has established medical eligibility criteria to assist in assessing such risks. Cardiovascular disease is a major concern, and for women with diabetes who have macrovascular or microvascular complications, nonhormonal methods are recommended. Studies of young women with diabetes and no vascular changes who are taking low-dose combined oral contraceptives (COCs) have been reassuring, although larger long-term studies are needed. There is little evidence that any changes in glycemic control caused by COCs are of clinical relevance. While low-dose COCs appear to cause minimal change in the lipid profile and may even be beneficial in this respect, there are some concerns in relation to progestogen only pills and injectable contraceptives in certain women. There is little evidence of best practice for the follow-up of women with diabetes prescribed hormonal contraception. It is generally agreed that blood pressure, weight, and body mass index measurements should be ascertained, and blood glucose levels and baseline lipid profiles assessed as relevant. Research on hormonal contraception has been carried out in healthy populations; more studies are needed in women with diabetes and women who have increased risks of cardiovascular disease.

Potential impact of oral contraceptive choice on myocardial infarction mortality and deep vein thrombosis

OBJECTIVES

To summarise the epidemiological evidence on the relationship between second- (OC2) and third-generation (OC3) oral contraceptives (OC) and the mortality associated with deep vein thrombosis (DVT) and myocardial infarction (MI), and to extrapolate and balance the evidence for these risks to the population of French OC users.

METHODS

All studies published on the risk of MI during OC2 and OC3 use were analysed. For DVT the Committee for Proprietary Medicinal Products public assessment report published in 2001 and more recent studies published on this topic were used. The estimates of odds ratios (OR) for risk of death from DVT or MI were extracted from the published manuscripts. ORs were used to calculate the aetiological fraction of risk for death from DVT and MI in the population; the relative impact of OC3 compared to OC2 use was expressed as an excess risk of death overall and by age group for French women.

RESULTS

Compared with OC2, the use of OC3 would prevent a maximum of 24 deaths from MI per year and induce a maximum of 16 deaths. Conversely, OC3 would induce 282-940 excess cases of DVT per year, resulting in 28-94 pulmonary embolisms and 3-19 deaths in the 4.7 million French OC users.

CONCLUSION

Balancing the evidence, it is difficult to conclude that the overall cardiovascular risk is significantly lower for either of the two OC schemes.

Safety of a New Oral Contraceptive Containing Drospirenone

New chemical entities must undergo rigorous, and preferably independent, safety and efficacy assessments before entry into the market. This is also true for oral contraceptives (OCs) given their extensive usage by healthy women and the safety concerns highlighted by the so-called 'third generation pill scare' in Europe a decade ago. This scare heightened patient and physician awareness of the increased risk of thromboembolic complications (mainly venous thromboembolism [VTE]) associated with OC use. Yasmin (ethinylestradiol 30 microg/drospirenone 3 mg [EE/DRSP]) is a novel OC that was demonstrated in clinical phase I-III studies to be highly effective in preventing pregnancy and to have a good safety profile. Nonetheless, clinical trials are not usually sufficiently powered to detect rare adverse events such as VTE to enable comparison with other OCs, which could allay fears and concerns about their inherent risks. Therefore, an extensive assessment of the VTE risk associated with EE/DRSP has been undertaken by reviewing data from the clinical development programme, postmarketing surveillance and spontaneous worldwide reporting, as well as information from other sources. Spontaneous worldwide reporting has revealed a VTE reporting rate of 5.1/100 000 women-years with EE/DRSP use. In contrast, 3-year interim results from a large, controlled, prospective postmarketing surveillance study suggest a VTE rate of 61/100 000 women-years for EE/DRSP, which is similar to the rates of 60/100 000 and 73/100 000 women-years for levonorgestrel-containing OCs and other OCs, respectively. When placed in context with potential biases and confounding factors that would inflate the perceived risk of VTEs with a novel OC, the VTE rate with EE/DRSP does not highlight any safety concerns. Furthermore, the risk of VTE with EE/DRSP or other OCs is far less than that associated with pregnancy and delivery (up to 800/100 000 women-years) or than other risks of daily living. Available data indicate that EE/DRSP is not associated with any increased risk of other serious adverse events such as hyperkalaemia, cardiac arrhythmia or birth defects. Nonetheless, caution should be exerted in prescribing EE/DRSP to women with conditions that predispose to hyperkalaemia.Overall, the safety data with EE/DRSP and other OCs indicate that these products have no negative impact on the risk of VTE (and other adverse events) in women who receive OCs for contraception.

Thrombophilias and gynaecology

In gynaecology, women are exposed to sex steroids when using oral contraceptives, hormone replacement therapy or when undergoing in vitro fertilization treatment and ovulation induction. Oral contraceptives and the use of hormone replacement therapy increase the risk of venous thrombosis. The risk is highest in the first year of use and higher among women with clotting defects. Women taking third-generation oral contraceptives have an almost twofold increased risk of venous thrombosis compared with those taking second-generation oral contraceptives. Inherited clotting defects, which are themselves risk factors of venous thrombosis, (e.g. factor V Leiden mutation, deficiency of protein C, protein S or antithrombin, high plasma levels of factor VIII, and prothrombin mutation) appear synergistically increase the risk of venous thrombosis caused by oral contraceptives. Recent studies also point to an interaction between hormone replacement therapy and coagulation defects in causing venous thrombosis. Emerging studies show that in vitro fertilization treatment and ovulation induction are also risk factors for venous thrombosis; the role of coagulation defects in this association is not yet clear.

Menorrhagia: an update

Menorrhagia is defined as a 'complaint of heavy cyclical menstrual bleeding occurring over several consecutive cycles'. Objectively it is a total menstrual blood loss equal to or greater than 80 ml per menstruation. It is estimated that approximately 30% of women complain of menorrhagia. Excessive bleeding is the main presenting complaint in women referred to gynecologists and it accounts for two-thirds of all hysterectomies, and most of endoscopic endometrial destructive surgery. Thus, menorrhagia is an important healthcare problem. Its etiology, investigation, medical and surgical management are described. In approximately 50% of cases of menorrhagia no pathology is found at hysterectomy. Abnormal levels of prostaglandins or the fibrinolytic system in the endometrium have been implicated. Effective medical treatments suitable for long-term use include intrauterine progestogens, antifibrinolytic agents (tranexamic acid) and nonsteroidal anti-inflammatory agents (mefenamic acid). Over the past decade there has been increasing use of endometrial destructive techniques as an alternative to hysterectomy. Their further refinement and the advent of fibroid embolization has increased the options available to women.

The effects of seven monophasic oral contraceptive regimens on hemostatic variables: conclusions from a large randomized multicenter study

We investigated the effects of ethinylestradiol dose (50, 30 and 20 microg) and progestogen type [desogestrel (DSG), gestodene (GSD), levonorgestrel (LNG) and norgestimate (NGM)] in oral contraceptives on 24 hemostatic variables. In a multicenter, randomized, comparative study, 707 healthy, nonsmoking, nulliparous women were treated for six cycles with one of the seven monophasic oral contraceptives tested. Significantly greater increases in prothrombin fragment 1+2 and factor VII (activity and antigen), were found in the DSG, NGM and GSD groups compared to the LNG group. Similarly, significantly lower levels of protein S (free and total) and increased APC-sr (endogenous thrombin potential based) were found in the same groups compared with the LNG group. In addition, the estradiol dose (50 vs. 30 microg) significantly influenced these parameters. All changes were within the normal range and have not been associated with an increased risk of venous thromboembolic event (VTE). However, raised levels of these variables are associated with prothrombotic states such as pregnancy. The significance of the haemostatic changes found in this study in relation to VTE risk remains to be determined, but results of this study probably cannot explain the differences in risk of VTE between OCs containing different progestogens.

Termination of pregnancy following panic-stopping of oral contraceptives

This study assessed characteristics of women presenting for termination of pregnancy subsequent to stopping combined oral contraceptive use in response to publicity-mediated fears regarding venous thromboembolism. Records of 400 women attending for pregnancy termination assessment were reviewed retrospectively. Panic-stopping of oral contraceptives was implicated in 9.5%. Nearly 50% of combined pill users claimed their pregnancy resulted from panic-stopping because of media-promoted fear of health risks, especially 'clots.' Panic-stoppers had significantly lower identified risk factors for venous thromboembolism than pill users who had not panic-stopped. The relative safety of third-generation pills is under debate. The risk-benefit ratio of contraceptive pills is overwhelmingly positive but practitioners must be vigilant in screening for risk factors and contraindications. Panic-stopping results in unwanted pregnancies with concomitant psychological distress and potential physical morbidity. In future situations where research findings may precipitate drug scares, we recommend recall of patients by their health provider, funded by the relevant health authority or pharmaceutical companies, to allow discussion of risks before the media is enabled to have access to the information.

Oral contraceptives and venous thromboembolism: a five-year national case-control study

The objective of this study was to assess the influence of oral contraceptives (OCs) on the risk of venous thromboembolism (VTE) in young women. A 5-year case-control study including all Danish hospitals was conducted. All women 15-44 years old, suffering a first ever deep venous thrombosis or a first pulmonary embolism (PE) during the period January 1, 1994, to December 30, 1998, were included. Controls were selected annually, 600 per year in 1994-1995 and 1200 per year 1996-1998. Response rates for cases and controls were 87.2% and 89.7%, respectively. After exclusion of nonvalid diagnoses, pregnant women, and women with previous thrombotic disease, 987 cases and 4054 controls were available for analysis. A multivariate, matched analysis was performed. Controls were matched to cases within 1-year age bands. Adjustment was made for confounding influence (if any) from the following variables: age, year, body mass index, length of OC use, family history of VTE, cerebral thrombosis or myocardial infarction, coagulopathies, diabetes, years of schooling, and previous birth. The risk of VTE among current users of OCs was primarily influenced by duration of use, with significantly decreasing odds ratios (OR) over time: <1 year, 7.0 (5.1-9.6); 1-5 years, 3.6 (2.7-4.8); and >5 years, 3.1 (2.5-3.8), all compared with nonusers of OCs. After adjustment for confounders, current use of OCs with second- (levonorgestrel or norgestimate) and third- (desogestrel or gestodene) generation progestins when compared with nonuse resulted in ORs for VTE of 2.9 (2.2-3.8) and 4.0 (3.2-4.9), respectively. After adjusting for progestin types and length of use, the risk decreased significantly with decreasing estrogen dose. With 30-40 microg as reference, 20 and 50 microg products implied ORs of 0.6 (0.4-0.9) and 1.6 (0.9-2.8), respectively (p(trend) = 0.02). After correction for duration of use and differences in estrogen dose, the third/second-generation risk ratio was 1.3 (1.0-1.8; p <0.05). In conclusion, use of OCs was associated significantly to the risk of VTE. The risk among current users was reduced by more than 50% during the first years of use. The risk increased more than 100% with increasing estrogen dose, and the difference in risk between users of third- and second-generation OCs, after correction for length of use and estrogen dose, was 33%.

Case-control studies on venous thromboembolism: bias due to design? A methodological study on venous thromboembolism and steroid hormone use

This study addressed methodological issues of epidemiologic studies on venous thromboembolism (VTE) to show how design decisions can affect the results. It examines the influence of a restricting to hospitalized and to "idiopathic" cases of VTE in case-control studies on VTE risk and oral contraceptive (OC) use and thereby the bias potential. The diagnostic processes and OC exposures of 1068 suspected cases of VTE were followed in 21 German centers from 1994 to 1999 and evaluated compared to population and hospital controls. Of 606 confirmed cases, 385 (65.5%) were hospitalized, 168 (27.7%) were "idiopathic." Comparing users versus nonusers of OCs, the odds ratio (OR) for VTE risk for all cases and controls was 3.38 and 5.44 for "idiopathic" VTE. For hospital cases and controls, the OR was 3.72 and 9.1 for "idiopathic" VTE. The risk ratio for third- vs. second-generation OCs was increased in the hospital base but not in the population base. It was concluded that restriction to hospitalized events and exclusions of certain cases overestimate the VTE risk of OCs. An evidence-based consensus on methodological standards and definitions in case-control studies on VTE and steroid hormone use is required.

Risk of venous thromboembolism from oral contraceptives containing gestodene and desogestrel versus levonorgestrel: a meta-analysis and formal sensitivity analysis

Controversy exists regarding whether oral contraceptives (OCs) containing desogestrel and gestodene are associated with an increased risk of venous thromboembolism (VTE) versus OCs containing levonorgestrel. We were interested in synthesizing the available data, exploring explanations for mixed results, and characterizing the degree of uncontrolled confounding that could have produced a spurious association. We performed a meta-analysis and formal sensitivity analysis of studies that examined the relative risk of VTE for desogestrel and gestodene versus levonorgestrel. Twelve studies, all observational, were included. The summary relative risk (95% CI) was 1.7 (1.3-2.1; heterogeneity p = 0.09). If real, the incremental risk of VTE would be about 11 per 100,000 women per year. An association was present when accounting for duration of use and when restricted to the first year of use in new users. However, in the sensitivity analysis, the association abated in many, but not all, scenarios in which an unmeasured confounding factor increased the risk of VTE three to fivefold and in nearly all examined scenarios in which the factor increased the risk 10-fold. The summary relative risk of 1.7 does not appear to be caused by depletion of susceptibles, but is sensitive to a modest degree of unmeasured confounding. Whether such confounding occurred is unknown. However, given this sensitivity, this issue probably cannot be settled unequivocally with observational data. In the absence of a definitive answer, this apparent increased risk, together with its uncertainty and small magnitude and its important consequences, should be considered when selecting an OC for a given woman.