Individuals who are diagnosed with HIV aged 50 years and above have as good a response to antiretroviral therapy as patients who are aged under 40 when they receive their HIV diagnosis, according to research presented as a poster to the 46th Interscience Conference on Antimicrobial Agents and Chemotherapy in San Francisco last week. However, the researchers from California found that even though older patients did well on HIV therapy, they were nevertheless more likely to progress to AIDS and die than younger patients.
A separate piece of research conducted in Spain found that although older age did not reduce the odds of a patient achieving and sustaining viral suppression with anti-HIV therapy, it did find that antiretroviral therapy yielded lower increases in CD4 cell count as patients aged.
HIV has traditionally been viewed as a younger person’s illness. But thanks to effective antiretroviral therapy many individuals with chronic HIV infection are now surviving into middle and, hopefully, older age. There is also some evidence of an increase in HIV incidence amongst older patients. Some investigators in the United States have suggested that the availability of erectile dysfunction drugs may be partly responsible.
Doctors in California wished to gain a better understanding of the characteristics of HIV infection in older patients. For the purpose of the study, they defined “older” as 50 years of age or above at the time of HIV diagnosis.
Over a six-year period (1998 – 2004) data were gathered on all new HIV diagnoses at eleven hospitals in California. Patients were divided into two groups on the basis of their age: the first group consisted of just under 500 patients who were aged 50 years or over at the time of their HIV diagnosis, and the second group was composed of almost 4,000 patients aged between 18 and 40 years at the time of HIV diagnosis.
Information was gathered for both groups of patients and compared regarding risk factors for HIV infection; baseline viral load and CD4 cell count; response to antiretroviral therapy; progression to AIDS; and death.
Some significant differences existed between older and younger patients at the time of their HIV diagnosis. Older patients were more likely to be male (84% vs. 75%, younger patients, p
When HIV was diagnosed, older patients had a median CD4 cell count of 229 cells/mm3 compared to a median count of 360 cells/mm3 in younger patients. This difference was statistically different (p
The investigators then compared how older and younger patients responded to potent antiretroviral therapy. Both groups of patients had comparable viral load before HIV treatment was initiated, but after six months of therapy significantly more older patients had a viral load below 500 copies/ml than did younger patients (85% vs. 66%, p
Despite having better virologic control of HIV, CD4 cell counts were lower amongst older patients than younger patients six and twelve months after starting HIV treatment by approximately 100 cells/mm3 (313 cells/mm3 vs. 415 cells/mm3; 350 cells/mm3 vs. 449 cells/mm3). This difference was maintained five years after treatment was initiated (483 cells/mm3 vs. 547 cells/mm3). No tests for statistical significance were provided by the investigators, but at all time points measured after the initiation of antiretroviral therapy, both younger and older patients had median CD4 cell counts high enough to suggest adequate protection against AIDS-defining illnesses.
Finally, the investigators compared outcome in their patients. They noted that older patients were significantly more likely to progress to AIDS (p 3.
A study conducted in Madrid produced broadly similar findings. It included 187 patients who had a CD4 cell count below 200 cells/mm3 and were completely naïve to antiretroviral drugs when HIV therapy was initiated. Although age had no effect on the likelihood of achieving and maintaining viral load for up to 18 months after starting antiretroviral drugs, each additional ten years in age significantly reduced (by 90%) a patient’s odds of achieving a CD4 cell count of 350 cells/mm3 after 18 months of HIV therapy (p = 0.02).
Navarro G et al. HIV infection in older patients: clinical, immunological, virological features and response to combination antiretroviral therapy. Forty-Sixth Interscience Conference on Antimicrobial Agents and Chemotherapy, San Francisco, abstract H-1397, 2006.
Resino S et al. Influence of age in HIV-infection outcomes among antiretroviral naïve patients with severe immunodeficiency during highly active antiretroviral therapy. Forty-Sixth Interscience Conference on Antimicrobial Agents and Chemotherapy, San Francisco, abstract H-1399, 2006.