Bayesian Analysis of the Factors Affecting the Interval between Blood Donations Using Cox's Shared Frailty Model: A Cross-sectional Study on a Sample of Blood Donors in Iran

Identify talented people to donate predisposed a major role in supplying healthy blood. If the time interval between donations decrease, the chance that voluntary of blood donation be a regular donor increase. The aim of this study was to determine factors affecting the interval between blood donations in a sample of first-time blood donors. Data of a Cross-sectional Study of 864 blood donors in Shahrekord Blood Transfusion Center were used. In survival analysis framework, the times of blood donations are recurrent events. To identify the risk factors affecting the survival time of the return intervals between donations, Cox model with shared gamma frailty was fitted to the data and estimate of the parameters obtained based on Bayesian approach using Markov Chain Monte Carlo algorithm by WinBUGS. ANOVA analysis on information related to age, sex, job and exposure with cigarettes in selected population from two city showed that the selected population in two cities is completely homogeneous and similar. And a Significant differences between the average concentration of lead in the nail of subjects under study in two cities is there (P<0.001).The average concentration of lead in nail samples in Isfahan was 0.1037 mg/g and the average concentration of lead nail samples in Chadegan city was 0.0875 mg/g. Because of better fitting of Cox's shared frailty model, the correlation between the intervals of blood donations was confirmed. With increasing awareness and culture, the lower-weight and higher-age people should be encouraged to donate more