HIV patients over 50 have comparable survival and immune response to under 50s: study findings

Older people with HIV aged 50 or above are just as likely as younger HIV-positive patients to benefit from HAART, according to two recently published studies.

One study, conducted by investigators at Johns Hopkins University in the US, and published in the 15 January 2003 edition of Clinical Infectious Diseases, compared survival rates between younger and older patients. The second study, undertaken at the Catholic University in Rome, and published in the January 2003 edition of AIDS, compared CD4 counts and HIV viral load between older and younger HAART patients. The US study found that older patients were slightly more likely to derive a survival benefit from HAART, whilst the Italian study concluded that older and younger HAART-patients were equally likely to see an increase in their CD4 count and a fall in their viral load.

In a retrospective study, investigators at Johns Hopkins HIV clinic in Baltimore compared mortality rates between 259 HIV-patients aged 50 or above, with deaths amongst a randomly selected cohort of 538 HIV-patients aged under 50. Patients were treated at the Johns Hopkins HIV clinic between 1990 and 2001, and were divided into four groups: older and younger patients who were treated with HAART; and, older and younger patients who were not treated with HAART.

At baseline, the older patients had a lower average viral load (20,000 copies/mL) than the younger patients (32,000 copies/mL). However, CD4 counts were significantly lower in older patients at 244 cells/mm³ versus 289 cells/mm³ in younger patients.

Investigators found that after three years of follow-up, almost 30% of the total study population of older patients had died compared to just 17% of the younger sample. What’s more, the average time to death was 663 days in patients aged 50 or above compared to 828 days in the under 50s.

When the results were further analysed and subject to controls for risk factors, including gender, sex between men, CD4 count at enrollment, and year of enrollment, investigators found a 2.36 higher risk of death in older untreated people than in younger untreated people. In the under 50s, treatment lowered the risk of death by a little over 58%, whilst in the over 50s by 30%.

However, when investigators repeated this analysis, excluding the younger patients, they found that treatment lowered the risk of death in older patients by 72%.

The investigators conclude that there “were no statistically or clinically significant differences in the survival rates between younger and older groups.” They suggest that some earlier studies have failed to find a marked benefit from HAART for older patients as they have concentrated on surrogate markers such as CD4 count, rather than the “direct measure of treatment response (mortality)”, which was employed in this study. They observe that the “ability of the thymus to repopulate CD4 cells is inversely correlated with age has been proposed as a mechanism for blunted T cell response to HAART in older individuals.”

However, an Italian study, involving 58 HIV-positive patients aged 50 or above and 116 patients aged 20-35, has found that both older and younger HAART patients are as likely to see an increase in their CD4 count and fall in viral load.

Investigators, at the Catholic University in Rome, enrolled patients between early 1997 and the end of 2000. In a prospective study, patients were treated with HAART and then evaluated to see if there was any difference between the number of older and younger patients experiencing successful immunological response to treatment (an increase in CD4 count to above 200 cells/mm³; virological response (viral load below 50 copies/mL); and a combined immuno-virological response.

At baseline, the over-50s had an average CD4 count significantly lower than that of the younger patients (range 108 – 111 cells/mm³ versus range 187 – 199 cells/mm³). However average viral load was comparable (between 80,000 and 60,000 copies/mL).

After six months, 69% of older patients saw their CD4 count rise to above 200 cells/mm³ compared to 79% of patients under the 35s. An undetectable viral load was achieved by 79% of the over 50s compared to 72% of younger patients.

Both immunological and virological success was achieved by 64% of older HAART-patients and 62% of the younger study population. However, multivariate analysis and adjustment for variables showed that there was no significant difference immunological, virological and immuno-virological success rates between the study populations.

“Our study confirms…that older patients under HAART experienced a successful immunological response comparable to that of younger individuals.” As regards immune function, the investigators note, “our older patients, starting HAART with a lower level of CD4 T cells, obtained a significant increment in their CD4 T cells count, with the same rapidity, intensity and persistence in time as observed in younger patients.”