Journal of School of Public Health and

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Background and Aim: Limitations of the traditional methods for assessing G*E interaction- including case-control studies- led to development of several non-traditional approaches. This study aims to assess the interaction between the genetic background (history of breast cancer in first degree relatives) and environmental influences (reproductive/menstrual factors) in patients with breast cancer we also compare the statistical efficiency and power of case-control and case-only designs in this setting.
Materials and Methods: In a matched case-control study in Mazandaran province (Iran), 250 incident biopsy-proven cases of breast cancer and 250 age-matched neighbor controls were interviewed. History of breast cancer in mother and/or sister(s) was taken as a surrogate measure of genetic predisposition, while age at first birth, parity, breast feeding, age at menarche and irregular menstruation were considered as relevant environmental factors. For the matched case-control design, we used a conditional logistic regression model to examine main effects and the G*E interaction. In the case-only design, logistic regression analysis was applied to obtain an estimate of G*E interaction, after checking for the independence assumption. We also calculated the power for detecting the interaction by matched case-control and case-only analyses.
Results: Age at first delivery did not meet the assumption of independence (p=0.02), and so was not included in the case-only analysis. No statistically significant interaction effect was seen in the case-control analysis, while case-only analysis showed significant negative interaction between disease in first-degree relatives on the one hand and parity and breast feeding on the other. We also detected a significant positive interaction between genetic predisposition and age at menarche. All the estimated 95% confidence intervals for OR in G*E interactions were narrower in the case-only analysis. For all factors, the power for detecting G*E interaction was greater in the case-only analysis compared to the case-control analysis, with ratios ranging from 1.08 to 2.23.
Conclusion: The case-only design is more efficient and powerful than the case-control design for detecting gene-environment interaction under the assumption of independence. Baseline disease risk, interactions and independent effects should be considered in using the control data for checking the assumption of independence. Considering the existence of another explanatory variable, eg. a mutant gene which may have passed unnoticed, would be the safest approach in a case-only study.

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Background and Aim: Previous studies show that disability and mortality due to cardiovascular diseases are closely related to socioeconomic status in a community. The objective of this study was to determine the relationships between socioeconomic factors and coronary artery disease (CAD) among people under 45 years old at Shahid Rajaei Hospital, Tehran, Iran.

Materials and Methods: This case-control study was conducted in Shahid Rajaei Hospital, Tehran, Iran in summer 2008. The participants were 100 CAD cases (<45 years old, mean age = 41.2 years 85% men) and 100 controls from among accompanying persons matched for age and gender. In order to assess the risk of factors related to such variables as educational level, occupation, income, social exclusion, social support, stress, exercise, nutritional status, smoking, etc, odds ratio (95% CI) was used. Multinomial logistic regression was used to assess the synchronic effect of the risk factors, and the t-test was used to find differences between means.

Results: The odds ratio (95% CI) for smoking vs nonsmoking was 3.9 (1.9-7.9) for CAD. Individuals with a low educational level showed an odds ratio of 2.7 (1.9-7-9), compared to those with a high educational level. Eating fruits and vegetables at least seven servings a week has an odds ratio of 2.7 (1.01-7.4) vs eating fewer servings. Occupation, job grade and physical activity had statistically significant relationships with CAD. Mean BMI was different between cases and controls. The disease had no significant association with stress, social support, social exclusion or income.

Conclusion: Smoking, a low educational level and eating small amounts of fruits and vegetables were the most important socioeconomic factors contributing to coronary artery disease. Policymaking and planning aiming at improving the socioeconomic situation of the people, particularly those under 45 years old, seem essential.

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  Background and Aim: There is some evidence that nutrition probably plays a role in the etiology of multiple sclerosis (MS). The present case-control study was conducted in the City of Tehran, Iran with the purpose of finding any possible relations between food groups and MS.

  Materials and Methods: In this case-control hospital-based study conducted in 2011 in the City of Tehran, data were collected on several variables including socio-economic status, life style, and food intakes of 70 MS patients and 140 controls matched for age and gender, through interviews and questionnaires. All the statistical tests were done using the SPSS software version 16. Logistic regression was used to calculate the odds ratio (OR).

  Results: After adjusting for confounding variables, it was seen that subjects in the upper tertile of intakes of the fruit group, tomatoes, other vegetables, and liquid oils, were significantly less likely to be suffering from MS disease, the odds ratio being 68% (OR: 0.32 95% CI: 0.13-0.79), 82% (OR: 0.18 95% CI: 0.05-0.65), 61% (OR: 0.39 95% CI: 0.93-0.16), and 94% (OR: 0.06 95% CI: 0.08-0.58), respectively. On the other hand, subjects shown to be significantly less at risk of the disease were those in the upper tertile of the intakes of non-liquid oil [ 1.58 times (OR: 2.58 95% CI: 1.05-6.33) ] and soft drinks [1.87 times (OR: 2.87 95% CI: 1.17-7.02)] (p for trend < 0.05).

  Conclusion: The findings of this study support the probable role of nutrition in preventing multiple sclerosis.