Women significantly more likely than men to have suboptimal adherence to HIV therapy

Women are more likely than men to have poor adherence to combination antiretroviral therapy (cART), according to Canadian research published in HIV Medicine. Adherence was monitored in a cohort of over 4000 people in British Columbia over 14 years. After controlling for injecting drug use (IDU) and ethnicity, 57% of women and 77% of men attained optimum 95% adherence.

“Our findings indicate that women are significantly less likely to achieve optimal adherence to cART than men,” comment the authors. “Although both Indigenous ancestry and history of injecting drug use have previously been found to impact adherence, our study shows that sex maintains a significant and independent effect on adherence.”

The researchers call for targeted research to identify barriers to adherence among women taking HIV therapy so that women-centred HIV care and treatment services can be developed.

Adherence is key to the success of cART. The best outcomes have been observed in people who take all, or nearly all, their doses at the correct time and the same way. Poor adherence (below 95% with older regimens) can lead to viral breakthrough and the emergence of drug-resistant virus.

Investigators from HAART Observational Medical Evaluation and Research (HOMER) cohort in British Columbia, Canada, designed a study to evaluate the effect of sex on adherence over a 14-year period (2000-14), while taking into account factors known to impact on adherence, especially IDU and indigenous ancestry.

“The study is unique in that it examines sex differences in cART adherence longitudinally in a large-population based cohort without the limitation of financial barriers to treatment, while accounting for IDU status, ethnicity, and elapsed time from initiation of therapy,” comment the authors.

The study population consisted of 4534 adults (20% women; 13% indigenous; 35% history of IDU) who started cART after 2000. Adherence was monitored via pharmacy refill at six-monthly intervals. Optimum adherence was defined as 95% of doses taken.

Individuals were followed for a median of 66 months.

Women were less likely than men to have optimal adherence (57% vs 77%, p < 0.001). The difference between women and men was greatest among non-indigenous individuals who did not have a history of IDU (70% vs 84%, p < 0.001).

Female sex was independently and significantly associated with suboptimal adherence after controlling for factors potentially associated with taking therapy, including age, history of IDU, indigenous ancestry, MSM and year of initiation of cART (AOR = 0.55; 95% CI 0.48-0.63).

The authors draw particular attention to the need to overcome a history of distrust, marginalisation and poor health outcomes that has arisen among Canada's indigenous population as a result of the history of colonialism.

“There is a need for culturally competent HIV-related care to support cART adherence and to build trust between Indigenous people and non-Indigenous HIV-care providers,” write the authors. “While injecting drug use does increase the likelihood of sub-optimal adherence among PLWH [people living with HIV], this study shows that sex maintains a central role in predicting adherence.”

The investigators believe their findings have implications for long-term targets to control the HIV epidemic.

“To reach the goals of the 90-90-90 and Treatment as Prevention, there is a need to identify where women are being lost along the Cascade of Care, under what circumstances, and how they can best be supported in their care at the varying levels of the Cascade,” conclude the authors. “Existing interventions to support cART adherence may not identify and care for the specific needs of women and, thus, may not be sufficient for the women who access them. The care of women, and barriers to women’s care along the Cascade, are particularly important to address if we are to meet the goals of UNAIDS’ 90-90-90 campaign to end AIDS by 2030.”