There were no apparent differences between older (aged 50 and up) and younger people living with HIV who initiated antiretroviral treatment in terms of CD4 and virologic responses, according to a study conducted at Maharaj Nakorn Chiang Mai Hospital in Thailand.
However, the study, which was presented at IDWeek 2014, found differences in blood cholesterol and sugar, but they were "not clinically relevant" according to study authors Romanee Chaiwarith, M.D., M.H.S., and Thanapat Kittipanyaworakun, M.D., of Chiang Mai University. In addition, there was an increased rate of renal and some metabolic complications in the older patients, but some of these differences were pre-existing.
The number of people living with HIV aged 50 and older is increasing. It has been estimated that by 2015 more than half of the people living with HIV in the U.S. will be over the age of 50 -- and their clinical management may be more complicated.
In the days before antiretroviral therapy, the progression of HIV disease had been observed to be much more rapid in older patients and this has remained the case in the era of antiretroviral therapy.
In addition, older patients generally have more health complications and, depending upon the setting, there may also be significant demographic differences between older and younger people living with HIV.
Responses to combination antiretroviral therapy in this population may be variable as well. CD4 cell counts are typically lower in older patients, and recuperative abilities may not be as robust. Conversely, older patients may be more settled than younger patients and better able to adhere to treatment.
However, many of the differences that have been previously reported in the literature may be specific to the population or demographic groups.
This retrospective study analyzed data from patients aged 18 and above who initiated antiretroviral therapy between January 2005 and December 2012 at the hospital, in order to compare people aged 50 and older living with HIV to those who were younger in terms of virologic and immunologic responses to antiretroviral therapy and adverse effects after antiretroviral therapy. Another objective was to compare the demographic groups, adverse events and metabolic complications between the age groups.
Out of 1,073 patients who initiated antiretroviral therapy at the hospital, 312 patients were randomly selected. Among the 312 patients, 209 were younger than 50 and 103 were 50 or older. The median age of the younger arm was 34 and the median age of the older arm was 54.5. The majority of participants were male.
There were significant differences in the mode of HIV transmission between the groups: 97.1% of the older group contracted HIV through heterosexual sex, while 18.2% of those in the younger arm contracted HIV though same sex sexual activity.
There were some significant differences in the number of underlying diseases/concurrent conditions in the two groups. In the younger group, 47.3% had no other concurrent diagnoses, compared to 33% in the older arm. Similar proportions had one or two diseases, but the older group more commonly had three or more diseases (13.6% versus 2.5%).
At baseline, the older patients were significantly more likely to already have hypertension, diabetes or dyslipidemia. Other concurrent infections such as hepatitis C, tuberculosis or opportunistic infections were similar between the groups, with the exception of hepatitis B virus infection and cryptococcosis, which were significantly more common among the younger population.
The median CD4 count at antiretroviral therapy initiation was 75 in the younger arm versus 90 in the older arm (the difference was not significant). Around 38% in both arms had CD4 counts below 50.
Initial Antiretroviral Therapy Regimen
The treatment regimens most participants started with were similar with nevirapine (Viramune) and lamivudine (3TC, Epivir) plus either zidovudine (AZT, Retrovir) or stavudine (d4T, Zerit) being the most common regimen. However, there were significantly more patients in the older group on a tenofovir (Viread) containing regimen (16.3% versus 32.0%).
Results After Antiretroviral Therapy Initiation
There was no significant difference in CD4 responses after antiretroviral therapy initiation between the two groups. The median time to reaching a CD4 count of 350 was 30 months in both arms. With follow-up out to 78 months, the median CD4 counts were up around 450-500 in both arms.
In the subset of patients for whom viral load data were available, the proportion of patients achieving an undetectable viral load at six months was 93.5% in the younger arm and 95.3% in the older arm.
- There were no significant differences between the rates of lipodystrophy, rash or drug-related liver toxicity.
- There may have been a trend toward more bone marrow suppression in the older arm, but it did not reach statistical significance.
- Rates of renal complications were higher in the older arm (as well as slightly elevated creatinine), but this was likely due to the greater use of tenofovir-containing regimens in this arm: 0.5% versus 5.8% (P = .006).
- Metabolic complications were significantly more likely in the older arm, but they had been more common at baseline as well: 19.6% versus 36.9% (P = .001).
- Rates of hypertension were similar in both arms, as were rates of diabetes mellitus.
- Dyslipidemia appears to have been the exception. While it was more common at baseline, and increased in both arms, a significantly greater proportion of participants in the older arm developed dyslipidemia on treatment: 13.4% versus 28.2% (P = .003).
In addition to the increased creatinine levels, LDL cholesterol and blood sugar levels were increased in the older arm as well, although the investigators believed that these differences "were not clinically significant."
There are a number of limitations to this study. First and foremost, the results in the Thai population may not be generalizable to other populations due to differences in weight, diet and lifestyle. In addition, other studies looking at more complex measures of immunologic recovery than simply CD4 counts suggest that there may be important differences between age groups.
However, this study does suggest that differences in mode of transmission, population and underlying diseases may be more important determinants, or at least cofactors, in the development of complications and comorbidities observed in older people living with HIV than the response to antiretroviral therapy itself.
Theo Smart is an HIV activist and medical writer with more than 20 years of experience. You can follow him on Twitter @theosmart.