Abstract:
Survival modelling is technique which exploits repeated measures of continuous
covariates to predict explanatory variables' effects on the response factor. The
survival modelling helps design interventions in the health sector, which has seen one
of its applications in the management of Human Immune Virus/ Acquired Immune
Deficiency Syndrome (HIV/AIDS). However, despite improvement in Anti-
Retroviral Therapy (ART) interventions over the years, the observed disease effects
(morbidity, progression and mortality) remain high and vary across geographical
borders. The general objective of the study was to model the survival time among
adult HIV/AIDS patients’ under ART in Moi Teaching and Referral Hospital
(MTRH) Kenya. Specifically, the study aimed at determining the mean and median
survival times among this cohort of patients, fit Cox proportional hazard regression
model to adult HIV/AIDS patients data and determine predictors of their survival. A
retrospective study design was adopted where a target population of 10,038 patients
who were on ART and were enrolled between January 2005 and January 2007 were
investigated for a ten years follow-up period. Survival and hazard functions were
used to determine the mean and median survival times. Kaplan Meier estimator was
used to measure the overall survival trend and compare the survival time by gender.
The Cox proportional hazard regression model (CPHRM) was fitted to the data using
log partial likelihood function. The log rank test and 95% confidence Interval (C.I)
were used to analyze the significance of the hazard ratios of each variable. The
sample was constituted of 2,985(29.7%) male and 7,053(70.3%) females. From the
data, censored patients consisted of 9,833(98%), while 205(2%) died. The results
showed that the median and mean survival times after ART initiation were 10.00 and
9.06 years, respectively. HIV severity with Unadjusted Hazard Ratio (UHR) [UHR
=0.729, p=0.032], level of education [lower UHR=0.952, p= 0.019], and ART perfect
adherence [UHR=0.668, p=0.004] positively influenced patient survival time.
Patient’s gender [male UHR= 1.633, p< 0.001] showed negative effect on patient
survival time. None of the patient's covariates were jointly significant predictor of
survival time in the multivariate Cox model. However, adjusting for other factors in
the model, HIV severity with Adjusted Hazard Ratio (AHR) [AHR1.18, p=0.735],
underweight measured by Body Mass Index (BMI) <18.5kg/m 2 in reference to 18.5-
<25kg/m 2 [AHR=1.65, p=0.847] patients’ male gender [AHR=1.884, p=0.19] and
ART perfect adherence at disease latter stage [AHR=1.393,p=0.498] increases the
risk of mortality by 18%, 65%,88.4% and 39.3% respectively. In conclusion, ART
perfect adherence enhance longer survival time in MTRH, The CPHRM fitted well to
study data hence described the data optimally. HIV severity, gender, level of
education and ART adherence were independent significant predictors of survival
time whereas age and BMI were not. The study recommends the initiation of ART
when CD4 count is at least 350mm 3 , male patients should do compulsory regular
screening to avoid late diagnosis and delayed presentation for ART medication and
MTRH should do sensitization on the importance of perfect adherence at early stages
of the disease.