The major focus of this project is the development of novel methodologies for the detection and estimation of gene-environment (G E) interactions for complex diseases. Recent advances in genetic studies have success- fully identified genetic variants that are associated with complex diseases such as cancer, heart disease and others. To further understand disease etiology, it is important to study the interplay between genetic and environ- mental risk factors. An important challenge to studying gene-environment interactions comes from the difficulty in environmental exposure assessments. Most environmental risk factors, such as diet, physical activity and air pollution, are measured imprecisely and self-reported diet or physical activity may suffer from substantial sys- tematic bias. Many environmental exposures are time-varying and their effects on health outcomes can be rather complicated. Existing statistical methods that deal with these types of complex environmental assessments have focused on main effects, and little has been developed for G E interactions. With these practical challenges in mind, our goal is to develop statistical methodologies that account for mea- surement error and time-varying exposures for GE interactions. In the presence of environmental measurement error, we will first evaluate the validity of na?1ve tests that ignore measurement error. We then extend regression calibration methods to interaction models for both exposures with classical measurement error and measure- ments subject to systematic bias. Typical examples for the latter include diet and physical activity self-report assessments. The proposed calibrated analyses are expected to be more powerful for testing GE interactions. For time-varying environmental factors such as air pollution, we propose novel functional data analysis methods that allow flexible modeling of environmental main effect and G E interactions. The functional model framework utilizes temporal patterns of exposures and can potentially improve power to detect G E interactions. The proposed methodological research is motivated by scientific problems from large-scale epidemiological studies (e.g., the Women's Heath Initiative) and will be directly applied to these projects.
The major focus of this proposal is the development of novel statistical methods to study gene-environment interactions that arise in genetic and genomic studies. We propose to develop analytical approaches to assess gene-environmental interactions when environmental exposures are imprecisely measured and/or time-varying.
|Fong, Youyi; Di, Chongzhi; Huang, Ying et al. (2017) Model-robust inference for continuous threshold regression models. Biometrics 73:452-462|
|Su, Yu-Ru; Di, Chong-Zhi; Hsu, Li et al. (2017) A unified powerful set-based test for sequencing data analysis of GxE interactions. Biostatistics 18:119-131|
|Su, Yu-Ru; Wang, Jane-Ling (2016) SEMIPARAMETRIC EFFICIENT ESTIMATION FOR SHARED-FRAILTY MODELS WITH DOUBLY-CENSORED CLUSTERED DATA. Ann Stat 44:1298-1331|
|Zubair, Niha; Kooperberg, Charles; Liu, Jingmin et al. (2015) Genetic variation predicts serum lycopene concentrations in a multiethnic population of postmenopausal women. J Nutr 145:187-92|
|Fong, Youyi; Di, Chongzhi; Permar, Sallie (2015) Change point testing in logistic regression models with interaction term. Stat Med 34:1483-94|
|Kratz, Mario; Marcovina, Santica; Nelson, James E et al. (2014) Dairy fat intake is associated with glucose tolerance, hepatic and systemic insulin sensitivity, and liver fat but not ?-cell function in humans. Am J Clin Nutr 99:1385-96|
|Di, Chongzhi; Crainiceanu, Ciprian M; Jank, Wolfgang S (2014) Multilevel sparse functional principal component analysis. Stat 3:126-143|
|Saegusa, Takumi; Di, Chongzhi; Chen, Ying Qing (2014) Hypothesis testing for an extended cox model with time-varying coefficients. Biometrics 70:619-28|
|Neuhouser, Marian L; Di, Chongzhi; Tinker, Lesley F et al. (2013) Physical activity assessment: biomarkers and self-report of activity-related energy expenditure in the WHI. Am J Epidemiol 177:576-85|