(Press-News.org) The results show that pills containing one of the newer types of progestogen hormone (drospirenone, desogestrel, gestodene, and cyproterone) are associated with an increased risk of VTE than pills containing older progestogens (levonorgestrel and norethisterone).
The researchers, based at the University of Nottingham, say this is "an important clarifying study" that "has sufficient power to provide reliable comparative findings for different formulations of combined oral contraceptives."
About 9% of women of reproductive age worldwide use oral contraceptives, rising to 18% of women in developed countries and 28% of women in the UK.
Although the increased clot risk associated with combined oral contraceptives is well known, previous studies have used different methods to examine this link, so the relative risks associated with different combinations remain inconclusive.
The researchers, led by Yana Vinogradova, Research Fellow in Medical Statistics at the University of Nottingham, tried to address these differences to help explain the range of results.
They used prescription data from two large UK general practice databases to measure the associations between use of combined oral contraceptives and risk of VTE in women aged 15-49 years, adjusting for other known risk factors.
They found that current users of any combined oral contraceptive are at an increased risk of VTE compared with non-users of similar age and health status.
Compared with women not using oral contraceptives, women using older pills, containing levonorgestrel, norethisterone, and norgestimate, had about two and a half times increased risk of VTE. Women using newer pills, containing drospirenone, desogestrel, gestodene, and cyproterone, had around a four times increased risk of VTE.
Risks for women using newer pills were around 1.5-1.8 times higher than for women using older pills.
In absolute terms, the number of extra VTE cases per year per 10,000 treated women was lowest for levonorgestrel and norgestimate (six extra cases), and highest for desogestrel and cyproterone (14 extra cases).
The authors stress that oral contraceptives are remarkably safe, and point out that the reported three times increased risk of VTE in women using oral contraceptives in their study is still lower than the up to 10-fold increased risk of VTE in pregnant women.
They say women on combined contraceptive drugs "should not stop using them, but should consult their doctor and review their current type of pill at their next appointment if there are any concerns."
This is an observational study so no definitive conclusions can be drawn about cause and effect.
Nevertheless, the authors say they believe this study "has the statistical power and sufficient adjustment for relevant confounders to be regarded as an important clarifying study, which has produced the most reliable possible risk estimates using currently available UK prescription data."
The results "provide evidence for relevant authorities concerned with prescribing guidelines or those involved with regulation of safety of medicines," they conclude.
Vinogradova's study "addresses important questions about the risk of venous thromboembolism in women taking oral contraceptives, concluding that the risk is around twofold higher than the risk associated with older contraceptives," writes Professor Susan Jick at Boston University School of Public Health in an accompanying editorial.
These results, combined with those of a similar Danish study published in 2011, "clarify inconsistencies in earlier studies and provide important guidance for the safe prescribing of oral contraceptives," she concludes.
INFORMATION:
James Rucker, a psychiatrist and honorary lecturer at the Institute of Psychiatry, Psychology and Neuroscience, King's College London, describes how these drugs "were extensively used and researched in clinical psychiatry" before their prohibition in 1967.
He explains that many trials of psychedelics published before prohibition, in the 1950s and 1960s, suggested "beneficial change in many psychiatric disorders".
However, research ended after 1967. In the UK psychedelic drugs were legally classified as schedule 1 class A drugs - that is, as having "no accepted medical ...
PHILADELPHIA -- HDL is the 'good cholesterol' that helps remove fat from artery walls, reversing the process that leads to heart disease. Yet recent drug trials and genetic studies suggest that simply pushing HDL levels higher doesn't necessarily reduce the risk of heart disease. Now, a team led by scientists from the Perelman School of Medicine at the University of Pennsylvania has shown in a large, forward-looking epidemiological study that a person's HDL function -- the efficiency of HDL molecules at removing cholesterol -- may be a better measure of coronary heart disease ...
A risk gene for dyslexia is associated with impairments in visual motion detection, according to a study published May 27 in The Journal of Neuroscience. Mutations in the gene DCDC2 have previously been associated with dyslexia, and this study found that dyslexics with an altered copy of the gene are unable to detect certain types of visual motion.
The researchers used a series of visual tests to compare typical readers with two groups of dyslexics -- one with and one without a specific deletion in the DCDC2 gene.
The subjects were presented with images of patterned ...
Oklahoma Medical Research Foundation scientists have pinpointed a cell that begins the process of scarring in fatty tissue. The findings cast new light on a biological process that occurs with obesity and can lead to diabetes.
"Scarring can be an important part of the healing process when a person suffers an injury," said OMRF's Lorin Olson, Ph.D., who led the research. "But excessive scarring, or fibrosis, can contribute to many dangerous health conditions."
The new research appears in the June 1 issue of the journal Genes & Development.
Using experimental models, ...
One of the major challenges of cocaine addiction is the high rate of relapse after periods of withdrawal and abstinence. But new research reveals that changes in our DNA during drug withdrawal may offer promising ways of developing more effective treatments for addiction.
Withdrawal from drug use results in reprogramming of the genes in the brain that lead to addictive personality, say researchers from McGill University and Bar Ilan University in a new study published in the Journal of Neuroscience.
"We inherit our genes from our parents and these genes remain fixed ...
New York, NY--May 25, 2015--Under the direction of Latha Venkataraman, associate professor of applied physics at Columbia Engineering, researchers have designed a new technique to create a single-molecule diode, and, in doing so, they have developed molecular diodes that perform 50 times better than all prior designs. Venkataraman's group is the first to develop a single-molecule diode that may have real-world technological applications for nanoscale devices. Their paper, "Single-Molecule Diodes with High On-Off Ratios through Environmental Control," is published May 25 ...
DALLAS, May 26, 2015 -- Drinking two or more alcoholic beverages daily may damage the heart of elderly people, according to research in the American Heart Association journal Circulation: Cardiovascular Imaging.
The study correlated weekly alcohol consumption among 4,466 people -- average age 76 -- to the size, structure and motion of various parts of the heart.
Researchers found:
The more people drank, the greater the subtle changes to the heart's structure and function.
Among men, drinking more than 14 alcoholic beverages weekly (heavy drinking) was linked with ...
DALLAS, May 26, 2015 - A vaccine may one day help lower blood pressure for up to six months, according to new research in the American Heart Association's journal Hypertension.
The study in rats may eventually provide a novel alternative to treat high blood pressure in people, who would not need to take a pill everyday.
"The potential of a vaccine for hypertension offers an innovative treatment that could be very effective for the control of non-compliance which is one of the major problems in the management of hypertensive patients," said Hironori Nakagami M.D., ...
A genetically engineered herpes virus can halt the progression of skin cancer by killing cancer cells and sparking the immune system into action against tumours, a landmark clinical trial has shown.
It is the first time that a phase III trial of viral immunotherapy has definitively shown benefit for patients with cancer.
The trial was led in the UK by researchers at The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust, and involved 64 research centres worldwide including the University of Oxford.
Researchers randomised 436 patients ...
BOSTON -- Carbon monoxide is known by many as a poisonous gas that causes brain injury and other neurological symptoms, including memory loss and confusion. But a new study led by investigators at Beth Israel Deaconess Medical Center (BIDMC) suggests the opposite may be true: When administered in small, carefully controlled amounts, carbon monoxide may actually protect the brain from damage following subarachnoid hemorrhage, a devastating stroke that results from bleeding in the brain.
Published online today in The Journal of Clinical Investigation (JCI), the new findings ...
