Short Communication: Effects of Age on Virologic Suppression and CD4 Cell Response in HIV-Positive Patients Initiating Combination Antiretroviral Therapy

Older HIV-positive patients may experience reduced benefit and increased toxicities from combination antiretroviral therapies (cART) due to late diagnosis, weakened immune systems, and other age-related physiological changes. This study investigates the effect of age on time to virologic suppression and CD4 cell count response to cART. Data were collected from a tertiary care immunodeficiency clinic in Toronto. HIV-positive patients with cART initiation after 1/1/1998 were included. Log logistic accelerated failure time models were used to estimate the effect of age on time to virologic suppression. Mixed linear models were used to evaluate CD4 cell response to treatment. A total of 502 patients were studied; 445 were less than 50 years old and 57 were age 50 or over. Of these 73% were male. Thirty-one percent started treatment with boosted protease inhibitors and 43% with nonnucleoside reverse transcriptase inhibitors. In a log logistic model adjusting for gender, immigration status, AIDS-defining illness, years since HIV diagnosis, baseline CD4 count and viral load, cART type, calendar year of cART initiation, and hepatitis C diagnosis, older age was not associated with time to virologic suppression (n=418, time ratio=0.94, p=0.20). In a multivariable mixed linear regression model adjusting for the same covariates, age was not associated with CD4 cell count response (n=418, β=0.34, p=0.96). Time to virologic suppression and immunologic response were not significantly different among older and younger patients. Further studies should investigate adherence, comorbidities, and regimen changes in addition to the current covariates.