Application of a change point model to atomic-bomb survivor data: Radiation risk of noncancer disease mortality

Nonaka Y, Shimizu Y, Ozasa K, Misumi M, Cullings HM, Kasagi F
Jpn J Biom 2012 (May); 32(2):75-96

Abstract

The dose response of noncancer disease mortality differs by time period for atomic-bomb survivors of the Life Span Study (LSS) in the Radiation Effects Research Foundation. We applied change point models and Akaike’s Information Criteria to the data of LSS Report 13 (Preston et al. (2003)), including 86,572 subjects and 31,881 noncancer disease deaths during 1950 to 1997. A model which incorporates a change point in the dose response but not in the background model showed results similar to those in LSS Report 13, which suggested that the baseline rate difference between proximal and distal survivors changed by time and the preferred dose response might be linear-quadratic in 1950-1967 and linear in 1968-1997. However, the present model, which incorporates change points in both dose response and background models, showed that there was little evidence to support a time-dependent change in the baseline rate difference between proximal and distal survivors. The preferred dose response was pure-quadratic in 1950-1964 and linear in 1965-1997. When the data were divided into cardiovascular disease (CVD) mortality and noncancer disease mortality other than CVD, the shape of the dose response did not differ by time period (linear for CVD and pure-quadratic for other than CVD).