Identifying Some Risk Factors for the Time to Death of the Elderly Using the Semi-Parametric Blended Model of Survival Analysis With Competing Risks

Abstract

Objectives As the population of elderly people in Iran is rising, determining the risk factors of their death is necessary. The purpose of this study was to identify the risk factors that reduce the survival time of elderly people. Methods & Materials In a longitudinal retrospective study, data of 510 elderly people aged over 60 years, who were admitted to Kashan's Golabchi nursing home from 2000 to 2012 were collected and analyzed. To identify some risk factors of time to death in elderly, semi-parametric mixture competing risk model in survival analysis was fitted to the data. To estimate the model parameters, Expand-Maximize-Compress (EMC) algorithm was used and parameters and their 95% confidence intervals were estimated using R software (version 3.3.1). Results In separate one-variable fitted models, the variables like high blood lipids (HR=1.04; CI =1.00, 1.31), history of myocardial infarction (HR=0.90; CI=1.04, 1.10), stroke history (HR=0.95; CI=1.00, 1.14), and deaths of elderly people with cardiovascular diseases were significant. In the fitted multivariate model, renal problems had a significant effect (HR=1.58; CI=1.77, 2.83) on time to death of elderly. Conclusion In single-variable fitting, age, history of myocardial infarction, history of stroke, and kidney problems were identified to have significant effects on the time to death of the elderly. Based on onevariable semi-parametric competing risk mixture fitted models, more significant risk factors for the time to death of elderly was identified when compared with a fitted multivariate mode to the data. This implies that the role of some independent variables can be explained by other independent variables. A B S T R A C T Objectivesecause the elderly population is increasing in Iran, awareness of various causes of death in the elderly is necessary. Certainly, with an increase in the number of elderly people, the mortality B rate in the community will be on the rise, followed by the increase in mortality rates in this age group [1].The present study aims to identify the risk factors that reduce the survival time of the elderly so that preventive measures could be considered in the identification, clinical trials, and therapeutic measures to eliminate serious risks and increase survival time for the elderly. The main purpose of this study was fitting a semi-para- metric blended model of survival analysis with competing risks for the elderly living in the nursing home and then estimating the parameters. Deaths in the elderly people due to cardiovascular diseases and other causes have been considered as competing risks. Methods & MaterialsThe research method was retrospective. Analysis of data was performed by studying 510 elderly people over 60 years of age, who were admitted to Kashan's Golabchi nursing home from 2000 to late 2012. Independent variables related to the time to death of the elderly included gender, age at the start of admission, blood pressure, blood lipids, mobility status, history of myocardial infarction, history of stroke, and ...