طراحی‌های تنها موردی و مورد- شاهدی در ارزیابی اثر متقابل ژن- محیط با استفاده از داده‌های سرطان پستان

  Background and Objectives: The role of gene-environment interaction in epidemiology has been widely considered. The traditional methods of studying the gene-environment interaction need appropriate control groups which their selection may be associated with some problems. Therefore, new methods have been created to study these interactions from which are the case-only designs. In this method, only the cases data are being used. In this study, gene-environment interaction in patients with breast cancer was investigated using the case-only and case-control designs .   Material and Methods: This study conducted in 2008, using two methods: matched case-control and case-only. Simple random sampling was used to select 300 patients with breast cancer in Shahid Mottahari Clinic for two aforementhioned designs. The control group for the matched case-control study was selected from the women referring to Shahid Mottahari Clinic. Data were analysed using lagistic regressian and conditional logistic regression.   Results: The confidence intervals and log likelihood in all variables in case-only design was better than the matched case-control. In case-only design, the standard error in the following variables age at menarche, the first delivery at the age of ≥34 yrs and /or nulliparity, the number of live births, use of oral contraception pills, and breastfeeding history were less than those in the matched case-control design. In case-only design, the P-value of the above-menthined variables was less than those of the matched case-control design.   Conclusion: The case-only design is an efficiency method for investigating of the interaction in terms of statistical study, sample size and the easily implementing.   Key words: Case-only, Case-control, Breast cancer, Gene-Environment Interaction     Funding: This research was funded by Shiraz University of Medical Sciences.   Conflict of interest: None declared.   Ethical approval: The Ethics Committee of Shiraz University of Medical Sciences approved the study.     How to cite this article : Moradzadeh R, Hasanzadeh J, Rajaaeifard A.R, Tahmasebi S, Golmohammadi P. Investigation on Gene-Environment Interaction using Breast Cancer Data a Case-Only and Case-control Designs. J Rafsanjan Univ Med Sci 2012 10(4): 267-78. [Farsi]