Pre-AIDS mortality in the Edinburgh City Hospital HIV Cohort

• Published in: Statistics in medicine Vol. 16; no. 21; pp. 2459 - 2474
• Main Authors: Seaman, Shaun R., Brettle, Ray P., Gore, Sheila M.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 15.11.1997; Wiley
• Subjects: Acquired Immunodeficiency Syndrome - diagnosis; Acquired Immunodeficiency Syndrome - epidemiology; Adult; Age Factors; Biological and medical sciences; CD4 Lymphocyte Count; Cohort Studies; Computerized, statistical medical data processing and models in biomedicine; Female; HIV Infections - mortality; Hospitals, Urban; Humans; Incidence; Male; Medical sciences; Medical statistics; Proportional Hazards Models; Regression Analysis; Risk Factors; Scotland - epidemiology; Substance Abuse, Intravenous - mortality; Time Factors; England; United Kingdom; Great Britain; Europe; Scotland; Infection; Virus; Human; Statistical method; Immunopathology; Viral disease; Mortality; Retroviridae; Lentivirinae; AIDS; Human immunodeficiency virus; Immune deficiency
• ISSN: 0277-6715; 1097-0258
• DOI: 10.1002/(SICI)1097-0258(19971115)16:21<2459::AID-SIM677>3.0.CO;2-8

In this paper, we look at the incidence and predictive factors of pre‐AIDS mortality among HIV‐infected individuals, and injecting drug users (IDUs) in particular, and compare IDUs with non‐IDUs. 627 patients (73 per cent IDUs) of the Edinburgh City Hospital HIV Cohort were enrolled pre‐AIDS and followed up until September 1994. Analyses were performed using cumulative hazard and cumulative incidence estimators for a competing risks model, the Cox proportional hazards model and the non‐parametric hazard estimator of Fusaro et al. (1993). The effects of age and CD4 T‐lymphocyte cell count, progressively depleted during HIV progression, were investigated. 60 deaths occurred in AIDS‐free patients during follow‐up; 25 were drug‐related deaths in IDUs. Pre‐AIDS mortality was higher among IDUs than non‐IDUs (p=0·07). The cumulative incidences of pre‐AIDS death after five years from enrolment were 11 per cent in IDUs and 6 per cent in non‐IDUs; the cumulative AIDS incidences were, respectively, 19 per cent and 32 per cent. After eight years, cumulative pre‐AIDS death incidence was 15 per cent among IDUs; cumulative AIDS incidence among IDUs was 35 per cent. Both groups had similar risks of medically‐related (non‐AIDS) − MRNA − death. Age and CD4 count were both individually predictive of MRNA death (relative risks (RRs) : 2·1 per decade of life, p<0·01; and 1·9 for each 100 cells per 100 μ lost, p<0·0001), although when used together age was less significant (RR 1·6, p=0·07). Neither was statistically significant for drug‐related mortality, although hazard may be lower in older individuals and may increase with falling CD4 count. The drug‐related mortality was 1·1 per cent: 2·3 per cent in the first two years after enrolment, and 0·4 per cent thereafter. We conclude that older HIV‐infected individuals are at greater risk of medically‐related death before AIDS. This risk increases as CD4 count declines. Drug‐related hazard may be greater in younger individuals and may increase as CD4 counts fall, but neither effect was formally significant. © 1997 John Wiley & Sons, Ltd.