The study marks the latest contribution to the ongoing debate surrounding HIV infection and hormonal contraception.
Researchers conducted a meta-analysis of 18 studies measuring rates of HIV infection among women using hormonal forms of contraception in sub-Saharan Africa. Individual participant data (IPD) was available for a total of 37,124 women aged 15-49, of whom 1,830 became infected with HIV.
"Contraception has profound benefits for women and societies," write the authors, "including reduced maternal and infant mortality and morbidity, empowerment of women to make choices about fertility, associated economic improvement, and a reduction in the number of babies born with HIV."
However, users of the injectable progestin contraceptive depot-medroxyprogesterone acetate (DMPA) appeared to be 50% more likely to develop an HIV infection than women who were not using any form of hormonal contraception.
Injectable hormonal contraception works by preventing ovulation and altering the lining of the womb so that pregnancy cannot occur. In particular, DMPA is used by around 41 million women around the world.
No increased risk of HIV infection was observed by the study authors among women using other forms of injectable hormonal contraception - norethisterone enanthate (NET-EN) or a different injectable progestin - or combined oral contraceptives (COC).
DMPA users were also 43% more likely than COC users to become infected with HIV, and 32% more likely than NET-EN users. The authors calculated these risk percentages after controlling the data for factors that could influence HIV risk, such as condom use and number of sexual partners.
Other recent studies concerning DMPA
The findings of the study are very similar to another recent study, reported on by Medical News Today. In this study, published in The Lancet Infectious Diseases, researchers associated DMPA use with an increased risk of HIV infection for women of 40%.
Another study, just published in the British Journal of Clinical Pharmacology, suggests that using any form of hormonal contraceptive - including DMPA - for at least 5 years could potentially increase a woman's risk of developing a rare brain tumor known as a glioma.
The researchers found "a statistically significant association between hormonal contraceptive use and glioma risk," although according to research team leader Dr. David Gaist, "a risk-benefit evaluation would still favor the use of hormonal contraceptives in eligible users."
"There is ongoing debate whether hormonal contraception (HC) increases the risk of HIV acquisition," write the authors of the latest study. "Strong evidence for an association would have important implications for sexual and reproductive health, particularly in areas of sub-Saharan Africa where the incidence of both HIV infection and unintended pregnancy remain high."
Study bias may have influenced findings
However, there are limitations to the method of meta-analysis used in the study. The authors note that "while IPD meta-analysis overcomes some of the problems associated with aggregated data, it cannot eliminate bias stemming from study design or conduct."
Associations between hormonal contraception and HIV infection were found to be weaker in studies with a lower risk of methodological bias than those with a high risk of bias. It could be possible that some of the perceived HIV infection risk could then be due to bias in the original studies.
"A randomized controlled trial would provide more definitive evidence about the effects of hormonal contraception, particularly DMPA, on HIV risk," the authors conclude.
"In the absence of definitive data, however," they add, "women with high HIV risk need access to additional safe and effective contraceptive options, and they need to be counseled about the relative risks and benefits of the available family planning methods."
In December, Medical News Today examined how global HIV and AIDS trends were affecting US-African aid policies.