For the analysis of cardiovascular and non-AIDS-defining malignancy deaths, we found hazard ratios within the same range when we considered the latest CD4 cell count measured at least 6 months before death (instead of the latest value available immediately preceding death).
Individuals with a high HIV RNA level, whether treated or not, had a significantly higher mortality from AIDS-defining and non-AIDS infectious causes (Table 4) even after adjusting for latest CD4 cell count. An association between liver disease mortality and a high HIV RNA level was only apparent among patients not on cART. Deaths from non-AIDS malignancies were not associated with HIV RNA level, whether the patient was receiving cART or not. Finally, deaths from cardiovascular causes were clearly associated with a higher HIV RNA level, regardless of cART (HR = 3.86, 1.57–9.51).
We did not correct type I error inflation for multiple comparisons, but most associations were highly significant (P < 0.001) and would allow for more than 50 comparisons, assuming an overall type I error of 0.05 in a conservative Bonferroni correction.
In this large collaboration of HIV seroconverter cohorts, non-AIDS-defining causes contribute to more than half of deaths especially serious non-AIDS-defining infections, malignancies, end-stage liver, cardiovascular and respiratory disease. We provide evidence for an association between these causes of death and several markers of immunodeficiency, with the exception of cardiovascular deaths which were, however, associated with higher levels of viral replication.
Our analysis confirms that latest CD4 cell count is associated with a higher mortality from conditions not traditionally defined as opportunistic, that is, liver diseases, non-AIDS infections, respiratory diseases, as well as non-AIDS malignancies, even when CD4 cell count measured at least 6 months before death was considered. In addition, we found a consistent and gradually increasing association between earlier markers of immunodeficiency, such as the nadir CD4 cell count, or duration of exposure to immunodeficiency, such as time spent with CD4 cell count less than 350/μl, and these specific causes of non-AIDS-defining deaths. Our analysis does not indicate a particular advantage of either CD4 cell marker compared to the latest CD4 cell count for non-AIDS-related outcomes. However, the consistent finding of a raised risk of non-AIDS-defining death and cumulative time spent with CD4 cell count less than 350/μl reveals important clinically relevant information and provides a strong argument that HIV-infected patients may benefit from early initiation of antiretroviral treatment to reduce the risk of AIDS and non-AIDS-related causes of death .
In this study, high HIV RNA, but not CD4 cell markers, was associated with a higher risk of CVD death. High HIV RNA level may be considered as a surrogate marker of HIV-related endothelial inflammatory activation, such as interleukin-6 or ultra-sensitive C-reactive protein, that may be promoted through various mechanisms .
Our study shows, in particular, a specific association of immune depletion and mortality from liver and cancer which may be additionally related to the result of ageing , HCV and hepatitis B virus (HBV) infections, tobacco, alcohol and IDU [27–29] as well as to toxicities from antiretrovirals .
Our study also shows that liver disease is a frequent cause of death in the cART era, now that patients are surviving to experience this competing cause of death. Indeed, immunosuppression is associated with more rapid progression to liver fibrosis and cirrhosis [13,31]. Mortality rates associated with end-stage liver disease may rise even further in the future due to the ageing of the HIV population, coinfections with viral hepatitis B and C and long-term cART-related hepatotoxicities .
A recent meta-analysis comparing the incidence of 28 types of cancer between HIV-infected patients, organ transplant recipients and the general population suggested that immunodeficiency was the main cause of cancer development . Although HIV is usually not considered as an oncogenic virus, HIV infection may contribute to carcinogenesis by persistent inflammation mediated by cytokines especially as immunosuppression provides the immunologic background that favours the development of non-AIDS-defining cancer [16,34] and leads to a reduced ability to the control of oncogenic viruses .
Studies exploring the relationship between immunodeficiency and non-AIDS-defining causes of death, however, have provided limited or biased evidence because they were based on small cohorts  or used models based on CD4 cell measurements immediately preceding death. This study confirms findings from prevalent cohorts reporting that the latest CD4 cell count and time since seroconversion were associated with deaths from both pre-AIDS [37,38] and non-AIDS causes. In addition, results from the Strategies for Management of Antiretroviral Therapy (SMART) trial clearly implicate immunodeficiency with the occurrence of several severe non-AIDS events, including major cardiovascular events, end-stage liver disease, malignancies and kidney complications [39,40].
Seroconverter cohorts, such as CASCADE, are better suited than prevalent HIV populations for studying the determinants of survival. As seroprevalent cohorts are recruited at various times after seroconversion with unknown HIV infection duration, early deaths might be missed leading to an underestimation of death rates and biased estimates of prognostic factors. In our analyses, the long duration of follow-up acquired for this population of seroconverters allowed us to assess four different approaches to model ‘exposure’ to immunosuppression, which ensured that immunosuppression had preceded death, rather than simply reflected the effects of terminal disease. Nevertheless, as all patients were under follow-up shortly after seroconversion, based on inclusion criteria they may represent a selected population with earlier HIV diagnosis, closer follow-up, optimal HIV management and favourable outcome, as compared with a recent publication from the same collaboration . In addition, patients started cART with a median CD4+ cell count above 320/μl, substantially higher than the level seen in many seroprevalent cohorts [41,42], reflecting the fact that patients were managed in an optimal setting in the context of early HIV diagnosis. However, though the overall mortality and the cumulative incidence of specific causes of death might underestimate that in the wider HIV-infected population [13,15,43–46], it is unlikely that the association between immunodeficiency and deaths from different causes would be greatly affected by this selection. Finally, the patients selected for this analysis might better reflect patients that are currently managed and followed-up by practitioners, as attested by a larger proportion of HIV acquisition in the more recent periods.
The quality of our database depended on the accuracy of recording of cause of death in each cohort, with 82% of causes that could be classified. Deaths were standardized using the Coding of Causes of Death classification (www.cphiv.dk/CoDe) , which ensured homogeneous coding for the reason of death across cohorts. Nevertheless, we did not apply the central adjudication process as in controlled trials, due to the fact that our categories of death were large and therefore misclassification was unlikely. However, each cohort uses its own methods to collect source data, and the process for selecting and validating an underlying cause of death may differ across cohorts, explaining that 18% of causes of death remained unknown. Anyway, in such a situation, the proportion of deaths attributed to AIDS have likely been overestimated as patients with different causes of death might have been more likely to be classified as AIDS-defining when their current CD4 cell count was low. As a result, this misclassification may lead to an underestimation of the relationship between non-AIDS-defining causes of death and immunodeficiency. Thus, we do not believe that this bias could explain the strong associations with immunodeficiency that we observed.
Treatment adherence was not available in the CASCADE dataset; however, any clinically relevant effect would be captured by our primary exposure variables (HIV RNA and CD4 cell count). Besides, traditional risk factors for specific non-AIDS-defining causes of death, such as tobacco consumption, could not be included as they are currently not pooled in CASCADE. It is difficult, however, to see how many of these factors would confound any relationship with immunodeficiency.
In conclusion, our results add to the growing body of evidence on the association of immunodepletion and important non-AIDS-related morbidity  and mortality and underline the need for continued large-scale collaborative HIV cohort collaborations. Our results also plead for the use of non-AIDS-defining death and morbidities as endpoints in clinical trials evaluating antiretrovirals. As HIV-infected patients in industrialized countries have higher lifestyle-related risks factors (e.g. alcohol and tobacco consumption) compared with the general population , programmes for aggressive management of lifestyle-related cardiovascular risk factors are paramount [48,49]. The burden of infections points to the need for harm reduction programs especially for IDUs who are at higher risk of dying from non-AIDS-defining causes  in addition to improved management strategies for the treatment of chronic HCV and HBV infections. Most importantly, our data provide additional arguments for HIV-screening programs of at-risk populations for the early detection and treatment of HIV infection.
Members of the CASCADE Collaboration are listed as follows:
Steering Committee: Julia Del Amo (Chair), Laurence Meyer (Vice Chair), H.C.B., G.C., Deenan Pillay, M.P., Magda Rosinska, C.S. and Giota Touloumi.
Coordinating Centre: K.P. (Project Leader), Sara Lodi, A.S.W., Abdel Babiker and Janet Darbyshire.
Clinical Advisory Board: H.C.B., Andrea de Luca, Martin Fisher and Roberto Muga.
Collaborators: Australia – Sydney AIDS Prospective Study and Sydney Primary HIV Infection cohort (John Kaldor, Tony Kelleher, Linda Gelgor, Tim Ramacciotti, David Cooper, Don Smith); Canada – South Alberta clinic (John Gill); Denmark – Copenhagen HIV Seroconverter Cohort (Louise Bruun Jørgensen, Claus Nielsen, Court Pedersen); Estonia – Tartu Ulikool (Irja Lutsar); France – Aquitaine cohort (Genevieve Chene, Francois Dabis, Rodolphe Thiebaut, Bernard Masquelier), French Hospital Database (Dominique Costagliola, Marguerite Guiguet), Lyon Primary Infection cohort (Philippe Vanhems), SEROCO cohort (Laurence Meyer, Faroudy Boufassa); Germany – German cohort (Osamah Hamouda, Claudia Kucherer); Greece – Greek Haemophilia cohort (Giota Touloumi, Nikos Pantazis, Angelos Hatzakis, Dimitrios Paraskevis, Anastasia Karafoulidou); Italy – Italian Seroconversion Study (Giovanni Rezza, Maria Dorrucci, Benedetta Longo, Claudia Balotta); Netherlands – Amsterdam Cohort Studies among homosexual men and drug users (Maria Prins, Liselotte van Asten, Akke van der Bij, Ronald Geskus, Roel Coutinho); Norway – Oslo and Ulleval Hospital cohorts (Mette Sannes, Oddbjorn Brubakk, Anne Eskild, Johan N Bruun); Poland – National Institute of Hygiene (Magdalena Rosinska); Portugal – Universidade Nova de Lisboa (Ricardo Camacho); Russia – Pasteur Institute (Tatyana Smolskaya); Spain – Badalona IDU hospital cohort (Roberto Muga), Barcelona IDU Cohort (Patricia Garcia de Olalla), Madrid cohort (Julia Del Amo, Jorge del Romero), Valencia IDU cohort (Santiago Perez-Hoyos, Ildefonso Hernandez Aguado); Switzerland – Swiss HIV cohort (Heiner C Bucher, Martin Rickenbach, Patrick Francioli); Ukraine – Perinatal Prevention of AIDS Initiative (Ruslan Malyuta); United Kingdom–Edinburgh Hospital cohort (Ray Brettle), Health Protection Agency (Valerie Delpech, Sam Lattimore, Gary Murphy, John Parry, Noel Gill), Royal Free haemophilia cohort (Caroline Sabin, Christine Lee), UK Register of HIV Seroconverters (Kholoud Porter, Anne Johnson, Andrew Phillips, Abdel Babiker, Janet Darbyshire, Valerie Delpech), University College London (Deenan Pillay), University of Oxford (Harold Jaffe).
CASCADE has been funded through grants from the European Union BMH4-CT97-2550, QLK2-2000-01431, QLRT-2001-01708 and LSHP-CT-2006-018949.
The funding body had no part in the design and conduct of the study; collection, management, analysis and interpretation of the data and preparation, review or approval of the manuscript.
We thank all patients, doctors, data managers and study nurses who were involved in the participating cohort studies. We thank Andrew Phillips and Abdel Babiker for valuable advice in the course of this study. We thank Valérie Journot and Ronald Geskus for their statistical support and Krishnan Bhaskaran for providing all necessary information on the database. We also thank Pierre Marie Preux for his daily support. CASCADE has been funded through grants from the European Union BMH4-CT97-2550, QLK2-2000-01431, QLRT-2001-01708 and LSHP-CT-2006-018949.
Contributors: G.C., B.M., R.T. and V.R. wrote the first draft of the study protocol (scientific hypothesis, objective, choice of study design and statistical methods, eligibility criteria). All members of the steering committee contributed to the final version of the protocol. B.M., R.T. and V.R. performed statistical analyses. All authors contributed to interpretation of the results. G.C. and B.M. wrote the first draft of the manuscript. All authors contributed to the final text. C.S., K.P., A.S. W., H.C.B., R.T., G.C. and B.M. contributed to the editing.
Conflict of interest statement: G.C. has received travel consultancy fees and honoraria from Bohringer Ingelheim, Roche and Gilead Sciences.
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Keywords:© 2009 Lippincott Williams & Wilkins, Inc.
antiretroviral therapy; bacterial infection; causes of death; CD4 cell count; hepatitis; highly active; human immunodeficiency virus/AIDS; neoplasm