Determining Gene­Environment Interaction Using Projected Score Method

Abstract

The present article proposes a new method for estimating multiplicative interactions between genetic and environmental factor on the risk of a dbease using projected score approach (Waterman and Lindsay {1996a, b)). First we review the existing methods for determining gene­environment interactions through case­control study and case­only study design. Then we discuss the proposed method based on projection theory. We derive an unbiased estimating equation for estimating the parameter of interest and then derive its asymptotic standard error. In addition, we derive a score statistic based on the derived estimating equation. The advantage of using the proposed method are : 1. Gain in efficiency of the parameter estimate and 2. Robustness to the other model parameters and gene­environment independence assumption. We apply the proposed method to a real case­control data on lung cancer. Finally, we compare the existing methods with the proposed method through a small simulation study which shows that the proposed method performs better than the existing methods in terms of efficiency in all situations irrespective of whether the genetic and environmental factor are independent in the population.