Epidemiology and Social: CONCISE COMMUNICATION
Poor CD4 response despite viral suppression is associated with increased non-AIDS-related mortality among HIV patients and their parents
Helleberg, Mariea,b; Kronborg, Gittec; Larsen, Carsten S.d; Pedersen, Gittee; Pedersen, Courtf; Obel, Nielsa; Gerstoft, Jana
aDepartment of Infectious Diseases, Copenhagen University Hospital, Rigshospitalet
bFaculty of Health Sciences, Copenhagen University, Copenhagen
cDepartment of Infectious Diseases, Copenhagen University Hospital, Hvidovre
dDepartment of Infectious Diseases, Aarhus University Hospital, Aarhus
eDepartment of Infectious Diseases, Aalborg University Hospital, Aalborg
fDepartment of Infectious Diseases, Odense University Hospital, Odense, Denmark.
Correspondence to Dr Marie Helleberg, Department of Infectious Diseases, Rigshospitalet, Blegdamsvej 9, DK2100 Copenhagen, Denmark. Tel: +45 35457726; fax: +45 35456648; e-mail: email@example.com
Received 15 September, 2012
Revised 30 October, 2012
Accepted 16 November, 2012
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Introduction: Poor CD4 response to antiretroviral treatment (HAART) is associated with increased mortality. We analyzed the impact of CD4 increase on non-AIDS-related morbidity and on mortality in HIV patients and their parents.
Methods: Mortality rates were estimated among 1758 virally suppressed patients in the Danish HIV Cohort Study after 2 years on HAART and among their parents (n = 1603). Analyses were stratified by pre-HAART CD4 count and CD4 increase. Incidence rate ratios (IRRs) of non-AIDS-related morbidity and mortality rate ratios (MRR) were analyzed using Poisson regression.
Results: CD4 increases less than 25 vs. more than 100 cells/μl was associated with increased mortality [MRR 3.5 (95% confidence interval (CI) 1.8–6.8)] even in individuals with pre-HAART CD4 cell count more than 250 cells/μl (MRR 3.2 (95%CI, 1.3–7.8). Mortality of parents of patients with poor CD4 response was also increased [MRR 1.5 (95%CI, 1.1–2.1)]. There was a trend towards association between poor CD4 response and increased risk of cardiovascular disease and cancer [IRR 1.6 (95%CI, 0.8–3.2) and 1.6 (95%CI, 0.6–4.8)].
Conclusion: Poor CD4 increase post-HAART is associated with adverse prognosis even in absence of severe immunosuppression. CD4 response in HIV patients is associated with mortality among their parents, thus poor CD4 response may be caused by genetic factors, which might also affect morbidity and mortality in the HIV-negative population.
AIDS-defining events are rare in virally suppressed HIV patients, even among those with low CD4 cell counts . However, inadequate CD4 response to successful antiretroviral therapy (HAART) is associated with increased risk of non-AIDS-related morbidity and mortality [2–5]. The mechanisms behind this are poorly understood.
In a cohort of virally suppressed HIV patients, we analyzed the association between non-AIDS-related morbidity and mortality and CD4 increase during the first 2 years of HAART. Further, to test the hypothesis that genetic factors may influence CD4 response and mortality, we analyzed the association between CD4 cell increase in patients and mortality among their parents.
HIV patients were identified from The Danish HIV Cohort Study (DHCS) . Dates and diagnoses of cardiovascular disease, liver disease and cancer were obtained from the National Hospital Registry and the Danish Cancer Register.
From The Danish Civil Registration System (DCRS) , we identified parents of patients and controls and obtained data on vital status and migration. Causes of death were retrieved from The National Registry of Causes of Death .
We included all individuals registered in DHCS, who were at least 16 years at HIV diagnosis, antiretroviral naïve and initiated HAART in 1996–2008, had CD4 cell count less than 500 cells/μl at HAART initiation, were virally suppressed (viral load <400 copies/ml) 1 year post-HAART initiation and during the following year and had a CD4 cell count available at HAART initiation and 2 years thereafter. The index date was date of the latter CD4 measurement.
From DCRS, we identified 13 controls for each HIV patient, matched on sex and age.
We identified all parents of patients and controls, alive on the date of HIV diagnosis of the patient to whom they were matched.
Outcomes were time to first admission or outpatient visit with cardiovascular disease, liver disease, cancer or death. Deaths were categorized as AIDS-related, non-AIDS-related or unnatural. Deaths were considered AIDS-related if AIDS was diagnosed within 1 year of death or if the cause of death was an AIDS-related cancer. Deaths caused by accidents, injuries, drug overdose or suicide were categorized as unnatural.
Time was calculated from index date until date of study outcome, emigration or 31 August 2010, whichever occurred first. For parents, the index date was date of HIV diagnosis of their offspring or of the patient to whom their offspring was matched.
We calculated incidence rates and mortality rates per 1000 person-years. Incidence rate ratios (IRRs) and mortality rate ratios (MRRs) were estimated using Poisson regression including the following confounders: sex, age (time updated), origin, route of HIV transmission, year of inclusion and time from HIV diagnosis to HAART, viral load (log10), smoking status, alcohol abuse and comorbidity (Charlson comorbidity index, excluding AIDS) prior to HAART. Pre-HAART CD4 count and an interaction term for pre-HAART CD4 and CD4 increase were also included, except for analyses stratified on pre-HAART CD4.
Analyses of MRR among controls and parents of controls were adjusted for sex, age and year of study inclusion.
SPSS statistical software, Version 15.0 (Norusis; SPSS Inc., Chicago, Illinois, USA) and Stata 8.0 (Stata Corporation, College Station, Texas, USA) were used for data analyses.
We included 1758 HIV patients, 1603 parents of patients, 22 854 controls and 31 527 parents of controls (Supplementary Tables 1+2, http://links.lww.com/QAD/A284). The CD4 increase the first 2 years of HAART was less than 25, 25–100 and more than 100 cells/μl in 74 (4.2%), 177 (10.1%) and 1507 (85.7%) patients, respectively.
Mortality by pre-HAART CD4 and CD4 increase
Patients with CD4 increase less than 25 and 25–100 vs. more than 100 cells/μl had increased mortality (Table 1). The association between pre-HAART CD4 count and mortality differed markedly with CD4 increase post-HAART (Table 2). Among patients with CD4 increase less than 25 cells/μl, mortality rates were high even when pre-HAART CD4 was more than 250 cells/μl. Among patients with CD4 increase 25–100 cells/μl, mortality increased with lower pre-HAART CD4 count. Mortality rates were low in all strata of pre-HAART CD4 counts if the CD4 count increased 100 cells/μl or more.
Estimates of association between CD4 increase less than 25 cells/μl and mortality were not significantly affected by comorbidity, alcohol abuse or smoking status (data not shown), and did not differ markedly in analyses including only non-injection drug users (non-IDUs), patients of Danish origin or individuals with pre-HAART CD4 cell count more than 250 cells/μl [MRR 2.6 (95% confidence interval, CI 1.4–5.1), 2.2 (95%CI, 1.2–4.1) and 3.2 (95%CI, 1.3–7.8), respectively]. Excluding individuals diagnosed with cancer 3 months or earlier, after index date (n = 199), did not change the estimates substantially [MRR 2.8 (95%CI 1.5–5.0)].
To exclude residual confounding by age or calendar period we compared mortality rates between controls, grouped by CD4 response of the HIV patient to whom they were matched, and found no differences in mortality (Table 1).
Causes of death
Non-AIDS-related natural causes accounted for 86% of all deaths [n = 101, mortality rate 10.1/1000 person-years (95%CI, 8.3–12.3), 3% were AIDS-related (n = 4, mortality rate 0.4/1000 person-years (95%CI, 0.1–1.1)] and 11% were due to unnatural causes [n = 12, mortality rate 1.2/1000 person-years (95%CI, 0.7–2.1)]. Individuals with CD4 increase less than 25 or 25–100 vs. more than 100 cells/μl had increased risk of non-AIDS-related death [MRR 4.0 (95%CI, 2.0–8.2) and 1.8 (95%CI, 1.0–3.1), respectively].
Mortality among parents
Mortality of parents of HIV patients with CD4 increase less than 25 vs. at least 25 cells/μl was increased (Table 1, Supplementary Figure 1, http://links.lww.com/QAD/A284), although the age and calendar distribution did not differ between these groups (Supplementary Table 2, http://links.lww.com/QAD/A284). Parents of non-IDUs and parents of patients with pre-HAART CD4 more than 250 cells/μl, also had increased mortality if the CD4 increase of their offspring was less than 25 vs. at least 25 cells/μl [MRR 1.6 (95%CI, 0.9–3.1) and MRR 1.8 (95%CI, 0.9–4.1)]. Mortality rates among parents of controls did not differ by CD4 response of the HIV patient to whom they were matched (Table 1).
There was a trend towards higher risk of cardiovascular disease and cancer among HIV patients with poor CD4 response (Table 1), but no association between CD4 increase and risk of liver disease or between pre-HAART CD4 cell count less than 100 vs. at least 100 cells/μl and risk of cardiovascular disease [IRR 1.3 (95%CI, 0.8–2.0)], liver disease [IRR 0.5 (95%CI, 0.2–1.1)] or cancer [IRR 1.0 (95%CI, 0.5–2.0)].
Among virally suppressed individuals, who survived the first 2 years post-HAART initiation, poor CD4 response was associated with increased mortality. Individuals with low pre-HAART CD4 cell count but adequate CD4 increase had lower mortality than those with a relatively high pre-HAART CD4 cell count but poor CD4 increase. Even among individuals with pre-HAART CD4 250–500 cells/μl poor CD4 response was associated with increased mortality. Mortality among parents of patients with poor CD4 response was also increased.
Our group has previously shown that incidence rates of myocardial infarction, lung cancer and head and neck cancer, which are strongly associated with lifestyle (e.g. smoking and alcohol) are increased among parents of HIV patients compared with matched controls [9–11]. Smoking is a major determinant of outcome among HIV patients ; however, in the present study, smoking, alcohol abuse or comorbidity did not affect the estimate of association between CD4 increase and mortality. Estimates did not change significantly when IDUs and their parents, who generally belong to the lower social strata, were excluded from analyses. However, we cannot rule out that lifestyle or environmental factors explain the association between poor CD4 response in patients and increased mortality among their parents. Analyses were adjusted for age and calendar period and we observed no differences in mortality among matched controls or their parents. It is thus possible that the ability to recover CD4 cells reflects genetic traits associated with cell renewal mechanisms and survival. HIV patients with poor CD4 response to HAART have increased activation of CD8 T cells and elevated markers of inflammation [13,14]. It is hypothesized that inflammation is both a cause of impaired immunological response and of excess morbidity and mortality among poor immunological responders. Genes involved in immune activation and T-cell apoptosis have been associated with CD4 increase during HAART [15–17]. It is possible that these genetic traits may also be associated with inflammation and increased mortality in the HIV-negative population.
The association between genes, immune recovery, inflammation, morbidity and mortality is not specific for HIV. Impaired CD4 reconstitution postrenal transplantation is associated with cyclooxygenase-II enzyme gene promoter polymorphisms  and with increased incidence of atherosclerotic events  and cancer . A CCR5 deletion protects against inflammation-associated mortality in dialysis patients  and reduces the risk of coronary artery disease .
In recent years, it has been recognized that atherosclerosis is an inflammatory process. We found a trend towards increased risk of cardiovascular disease among HIV patients with poor CD4 response, which is similar to findings from the Athena cohort , whereas Achhra et al. found no association between CD4 metrics and cardiovascular events in a population in which 20% were viraemic.
Poor CD4 increase was associated with higher incidence of cancer. Although not statistically significant, the finding is in agreement with previous studies showing that low CD4 counts are associated with increased risk of AIDS-related and non-AIDS-related cancer . We ruled out malignancy as a confounder causing both poor CD4 response and increased mortality by reanalyzing the data after exclusion of individuals diagnosed with cancer 3 months or earlier, after the index date.
In contrast to previous studies , we found no association between CD4 increase and risk of liver disease. This discrepancy is probably explained by exclusion of individuals diagnosed with liver disease prior to index date in our analysis. Liver fibrosis can cause lymphopenia, and thus analyses including individuals with prevalent liver fibrosis may yield different estimates of associations between low CD4 cell count and liver disease .
The study has some limitations. The number of study outcomes was rather small, which limited statistical power. The index date was 2 years post-HAART initiation and thus results can only be generalized to individuals surviving this period. We did not have data on socioeconomic measures and were unable to discern whether genetic, social or both factors were responsible for the increased mortality among parents of patients with poor CD4 increase. Measurements of markers of inflammation were not available.
We defined viral suppression as viral load less than 400 copies/ml. Residual viraemia may cause poor CD4 response to HAART, but since treatment intensification does not increase CD4 counts among immunological nonresponders, it is unlikely to be the main cause . ‘Blips’ of viraemia are associated with risk of treatment failure ; however, as treatment failures are rare in our cohort , we do not believe that virological failure explained the poor prognosis among individuals with poor CD4 response and their parents.
We conclude that poor CD4 response is associated with adverse prognosis even in individuals without severe immunosuppression at HAART initiation, whereas individuals, with a low pre-HAART CD4 count, who survive the following 2 years with adequate CD4 increase, do not have increased mortality. Genetic factors may influence CD4 response and risk of morbidity and mortality. These factors may also affect morbidity and mortality in the HIV-negative population.
All of the authors contributed to the conception and design of the study and the analyses and interpretation of the data. The article was drafted by M.H., J.G. and N.O. and was critically reviewed and subsequently approved by all authors.
We thank the staff of our clinical departments for their continuous support and enthusiasm.
Conflicts of interest
N.O. has received research funding from Roche, Bristol-Myers Squibb, Merck Sharp & Dohme, GlaxoSmithKline, Abbott, Boehringer Ingelheim, Janssen-Cilag, and Swedish Orphan. C.P. has received payment for lectures from Abbott, Merck Sharp & Dohme and Gilead, and received funding for conference participation from Bristol-Myers Squibb, Jansen Pharma/Tibotec and Merck Sharp & Dohme. C.S.L. has received payment for lectures from Janssen-Cilag, Merck Sharp & Dohme, Sanofi-Pasteur and Glaxo-Smith-Kline and received research grants from Baxter and Crucell-SBL vaccines. J.G. has received research funding from Abbott, Roche, Bristol-Myers Squibb, Merck Sharp & Dohme, ViiV, Swedish Orphan and Gilead. M.H., G.K. and G.P. report no conflicts of interest.
Funding: No funding sources were involved in study design, data collection, analysis, report writing, or the decision to submit the article.
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