@misc{oai:repo.qst.go.jp:00079036,
 author = {Doi, Kazutaka and Yoshinaga, Shinji and Doi, Kazutaka and Yoshinaga, Shinji},
 month = {Feb},
 note = {Since the Fukushima nuclear power plant accident, there is an increasing interest in low-dose, long-term radiation exposure in the field of radiation effect research, and epidemiological data using cumulative radiation dose is being analyzed. Cumulative exposure covariates included in statistical models are dependent on the strong and implicit assumption that risks from exposure in the different periods are equal throughout study span.
A new approach of weighted cumulative exposure for effect modification was proposed. In this proposed approach, cumulative exposure is considered as a combination of single exposure components in different time periods, and weighted cumulative exposure is calculated as the weighted summation of single doses. Exponential functions were assumed for the weight function and parameters included in the weight function were also estimated with the other parameters in the parameter optimization procedure. The performance of the proposed approach was evaluated through simulation studies and applied to a long-term cohort study of cancer mortality among female nuclear weapons workers.
Based on the results of simulation studies, it was suggested that the proposed approach was almost unbiased in the situation where the sample size exceeds 1000 and the change in sensitivity is monotonous. When the approach was applied to female nuclear worker data, a slight decreasing trend in breast cancer risk with increasing age at exposure was observed., The 4th International Symposium of the Network-type Joint Usage/Research Center for Radiation Disaster Medical Science},
 title = {Parametric weighting approach for effect modification by age at exposure in cumulative covariates},
 year = {2020}
}