Application of Joint Modeling for Growth Model and Time-to-Event Analysis

• Activity Number: 440
• Type: Contributed
• Date/Time: Wednesday, August 5, 2009 : 8:30 AM to 10:20 AM
• Sponsor: Section on Statistics in Epidemiology
• Author(s): Wan-Ling Hsu*+ and Kazuo Neriishi and Tatsuyuki Kakuma and Yuko Araki
• Companies: Radiation Effects Research Foundation and Radiation Effects Research Foundation and Kurume University and Kurume University
• Keywords: radiation ; WBC ; joint modeling ; growth model ; relative risk

Abstract

The study applied a joint model, combining growth model for white blood cell (WBC) and time-to-event analysis, to examine the causal association among radiation, inflammation, and solid cancer for A-bomb survivors. A total of 8,177 survivors were selected and followed up from 1964 to 2001. Among the participants, there were 64% females, 39% ever smokers, and 26% with solid cancer incidence. The correlation of longitudinal WBC counts showed a positive but declining association between periods. Radiation and smoking were significant risk factors for elevated WBC. The hazard model indicated that the relative risks of radiation, smoking, and WBC (95% CI) were 1.38 (1.28-1.48), 1.59 (1.48-1.69), and 1.25 (1.10-1.43), respectively. In conclusion, there was apparent indication that radiation and smoking, as well as chronically elevated WBC, resulted in higher risk of solid cancer.