HIV Levels Differ in Men and Women

In 1996, the Centers for Disease Control (CDC) announced the first declines in AIDS deaths among men since the beginning of the epidemic. During the same time period, AIDS deaths among women increased by 3%. The situation improved in 1997 when women experienced a 37% decline in AIDS-related deaths. This still was not equivalent to men, who experienced a 47% decrease in AIDS deaths during the same period.

The reasons why women have not fared as well as men have traditionally been assumed to be social rather than biological, with women being diagnosed later and having less access to health care. The natural history of HIV disease does not appear to be different between the sexes. However, results of two recent studies indicate that there may be a gender difference in viral load levels and disease progression. Women with equivalent viral load values have been found to have lower CD4 cell counts than their male counterparts.

Half the Viral Load but Equal Progression

This summer, Homayoon Farzadegan, Ph.D., of Johns Hopkins University in Baltimore, presented a study of intravenous drug users from a community clinic at the World AIDS Conference in Geneva (abstract 13384). (Dr. Farzadegan's report has now been published in The Lancet, Nov. 7, 1998, pages 1510-4). Frozen blood samples from 527 patients from 1988-1989 and follow-up samples from 285 patients from 1992-1993 were analyzed.

At the same or similar CD4 cell counts, median viral load values for women were approximately half those for men. Time to CDC-defined AIDS was similar for both genders, which indicates that women with lower viral loads progress to AIDS as quickly as men with higher viral loads. Women with the same viral loads as men had a 1.6-fold higher risk of progressing to AIDS; or equivalently, women with half the viral load of men had a similar time to AIDS as men. In the study group, AIDS manifestations, natural history of the disease, AZT use, illegal drug use and approximate time of infection were all comparable in the two genders.

It is unclear why women have lower HIV levels than men. Dr. Farzadegan suggested that women may be capable of clearing the virus faster than men, but that the damage to the immune system has already been done. In their article in The Lancet, the researchers stated that these results are best viewed not as showing differences in time to AIDS by gender but rather as indicating a different relationship between viral load and disease in women.

The Public Health Service's "Guidelines for the Use of Antiretroviral Agents" recommend offering therapy at viral loads of 10,000 copies/ml as measured by bDNA (20,000 copies/ml by PCR) or greater. However, the Guidelines were developed based on data predominantly from men. It would take women longer to progress to a viral load of 10,000 copies/ml (bDNA) than men, putting women at a disadvantage as to when treatment is initiated. According to the principal investigator of the study, David Vlahov, Ph.D., of Johns Hopkins, "Women have a lower viral set point than men. Therefore, we have to move the viral load levels in the Guidelines down for women if we want them to have the same benefit as men." He concluded, "Let's stop treating women like they're men and start treating women like women."

Claudia Brabazon, Sc.D., of the University of Toronto, presented a parallel study at the 38th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) last September. It analyzed data on close to 7,000 HIV-positive individuals from the Ontario Ministry of Health Database (abstract I-257). In this cohort, treated and untreated women were also more likely to have lower viral loads than men. There were no significant gender differences in CD4 cell counts. The analysis controlled for the effect of treatment and time of infection. Dr. Brabazon stated, "The assumption is that there is not going to be a gender difference, so you treat everyone the same. When you see something like our study showing that women have physiologically for whatever reason, both on and off therapy, lower viral loads, but they seem to be progressing at the same rate, you would think logically that you have to start treating women at a different time, at a different viral load."

Back to GMHC Treatment Issues November 1998 contents page.