@article {7145,
	title = {An Empirical Comparison of Joint and Stratified Frameworks for Studying G {\texttimes} E Interactions: Systolic Blood Pressure and Smoking in the CHARGE Gene-Lifestyle Interactions Working Group.},
	journal = {Genet Epidemiol},
	volume = {40},
	year = {2016},
	month = {2016 Jul},
	pages = {404-15},
	abstract = {<p>Studying gene-environment (G {\texttimes} E) interactions is important, as they extend our knowledge of the genetic architecture of complex traits and may help to identify novel variants not detected via analysis of main effects alone. The main statistical framework for studying G {\texttimes} E interactions uses a single regression model that includes both the genetic main and G {\texttimes} E interaction effects (the "joint" framework). The alternative "stratified" framework combines results from genetic main-effect analyses carried out separately within the exposed and unexposed groups. Although there have been several investigations using theory and simulation, an empirical comparison of the two frameworks is lacking. Here, we compare the two frameworks using results from genome-wide association studies of systolic blood pressure for 3.2 million low frequency and 6.5 million common variants across 20 cohorts of European ancestry, comprising 79,731 individuals. Our cohorts have sample sizes ranging from 456 to 22,983 and include both family-based and population-based samples. In cohort-specific analyses, the two frameworks provided similar inference for population-based cohorts. The agreement was reduced for family-based cohorts. In meta-analyses, agreement between the two frameworks was less than that observed in cohort-specific analyses, despite the increased sample size. In meta-analyses, agreement depended on (1) the minor allele frequency, (2) inclusion of family-based cohorts in meta-analysis, and (3) filtering scheme. The stratified framework appears to approximate the joint framework well only for common variants in population-based cohorts. We conclude that the joint framework is the preferred approach and should be used to control false positives when dealing with low-frequency variants and/or family-based cohorts.</p>},
	issn = {1098-2272},
	doi = {10.1002/gepi.21978},
	author = {Sung, Yun Ju and Winkler, Thomas W and Manning, Alisa K and Aschard, Hugues and Gudnason, Vilmundur and Harris, Tamara B and Smith, Albert V and Boerwinkle, Eric and Brown, Michael R and Morrison, Alanna C and Fornage, Myriam and Lin, Li-An and Richard, Melissa and Bartz, Traci M and Psaty, Bruce M and Hayward, Caroline and Polasek, Ozren and Marten, Jonathan and Rudan, Igor and Feitosa, Mary F and Kraja, Aldi T and Province, Michael A and Deng, Xuan and Fisher, Virginia A and Zhou, Yanhua and Bielak, Lawrence F and Smith, Jennifer and Huffman, Jennifer E and Padmanabhan, Sandosh and Smith, Blair H and Ding, Jingzhong and Liu, Yongmei and Lohman, Kurt and Bouchard, Claude and Rankinen, Tuomo and Rice, Treva K and Arnett, Donna and Schwander, Karen and Guo, Xiuqing and Palmas, Walter and Rotter, Jerome I and Alfred, Tamuno and Bottinger, Erwin P and Loos, Ruth J F and Amin, Najaf and Franco, Oscar H and van Duijn, Cornelia M and Vojinovic, Dina and Chasman, Daniel I and Ridker, Paul M and Rose, Lynda M and Kardia, Sharon and Zhu, Xiaofeng and Rice, Kenneth and Borecki, Ingrid B and Rao, Dabeeru C and Gauderman, W James and Cupples, L Adrienne}
}
