Iranian Journal of Epidemiology
Year:2006 | Volume:1 | Issue:3|Papers Count:9

Background & Objectives: This investigation was prompted by the growing importance of nested case-control studies and the increasing frequency with which they are done in epidemiologic research. After a brief explanation of nested case-control studies, we evaluate the trends in research methodology over the last decade, especially with regard to cohort, case-control, and nested case-control designs.Methods: Data for this study were extracted from the PubMed database, using these keywords: Nested Case- Control, Risk-Set Sampling and Density Sampling. The search was confined to the 10-year period from 1996 to the end of 2005. As for other methodologies, we used keywords Cohort and Case-Control for a search over the same time period. The search itself was performed on April 25, 2006.Results: We found 2011 articles reporting nested case-control studies. There were 95 such articles in 1996; the number had increased to 289 in 2005. Case-control and cohort designs accounted for 68456 and 60479 articles, respectively. The number of case-control articles rose from 4378 in 1996 to 10270 in 2005, while that of cohort articles increased from 2981 to 9771 over the same period.Conclusions: The number of cohort and nested case-control articles followed similar upward trends over the last decade and their rate of increase was greater than that of simple case-control articles.

Background & Objectives: There is no shortage of evidence linking coronary heart disease (CHD) to various genetic and environmental factors. Nonetheless, exploring the familial aggregation of major risk factors in the Iranian population could add valuable information to the existing body of knowledge.Methods: We received data on 656 families (1614 individuals) from the Provincial Health Authority in Kerman. The data had been originally collected in 0 nationwide non-communicable disease control project, under the auspices of the Health Ministry's Public Health Deportment. In this study, we divided subjects into high- and low risk groups based on the 75th percentiles of risk factor levels. Using a random-effect Poisson regression model, we looked at the association between risk factors within families. In all models, the risk ratios (RR) were adjusted for the age gap between parents and children.Results: Excessive weight in children showed a stronger association with overweight in the father than with the same problem in the mother (RR:2.35 versus 1.59). Risk of high blood pressure in the father was significantly related to the risk in the mother and the child. The risk of high blood glucose showed a significant association only between parents. Similarly, hypercholesterolemia did not show a significant association between parents and, C children, but its RR in parent-parent associations was around 2. We did not find any significant familial aggregation for smoking. However, physical exercise in mothers doubled the rate of exercise. in other family members.Conclusions: Although our sample size was relatively small, we found stronger associations within parent couples than between parents and children. This implies that common lifestyle may be a more prominent factor than genetic make-up.

Background and objectives: Data on transitions in health status are among the most important types of information used for promotion of health and social development. Health transition comprises two elements: demographic and epidemiologic transition. This paper depicts the health transition in I.R. Iran over the last few decades.Methods: We used demographic data gathered over the last 45 years in order to get an idea of the demographic transition. Several other sources were used to gather data on mortality and fertility patterns, occurrence of communicable and non-communicable diseases, etc to trace epidemiologic transition.Results: Indices relating to mortality and fertility patterns have undergone marked changes parallel with rising income levels, urbanization, industrialization, and access to health care. Also notable are decreasing under-5 and maternal mortality rates, aging of the population, and a shift from communicable to non-communicable diseases.Conclusions: Because of the uneven rate of social development, epidemiologic transition has followed varying patterns across different regions. It is crucial that these differences be taken account of in future health programs.

Background & Objectives: Considering the lack of adequate basic information on risk factors for road traffic injuries in Iran, a study was conducted to determine the association between potential risk factors and the incidence of injuries in motor vehicle drivers.Methods: We performed a population-based case-control study on Qazvin-Loshan road. Risk factors related to injury incidence were compared between 175 cases and 175 controls. Cases were drivers recently injured in road accidents. Controls did not have any injury and were selected systematically while the study was being conducted. Injury was defined as trauma needing medical or surgical treatment. Information was obtained through police reports and interviews with cases and controls. Data were analyzed by two methods; bivariate analysis (crude) and by a multivariate unconditional logistic regression model.Results: In bivariate analysis, risk factors for road traffic injuries risk were failure to wear seat belts or protective helmets, ejection from vehicle, severity of collision, number of crashes, motorcycle vs. other motor vehicle accidents, fire, rain and fog, and collision with fixed objects. In the logistic model, factors such as seat belt or helmet use with OR= 0.619 (0.376-1.018), ejection from the vehicle with OR= 2.952 (1.235-7.056), severe collision with OR= 5.413 (2.865-10.224), motorcycle vs. other motor vehicle accident with OR= 3.164 (1.05-9.537) and raining and fog vs. good weather with OR= 4.562 (1.663-12.514) were found to influence injury incidence. There was an interaction between severity of collision and weather status.Conclusions: Better speed control, use of seat belts or helmets, not using motorcycles for road travel and equipping vehicles with fire extinguishing capsules are recommended to reduce road accident injuries.

Background & Objectives: Multiple Sclerosis (MS) is the most prevalent autoimmune disease of the nervous system in young adults. There are currently more than 30000 cases in Iran and the number is increasing everyday. The objective of this study was to measure the amount of vitamin and mineral intake in MS patients and to compare it with reference values.Methods: We randomly selected 108 relapsing-remitting MS patients from the Iranian MS society in Tehran in 2005. Two questionnaires- covering personal information and medical data- were filled for each patient. Food intake was assessed by three 24-hour recalls and a quantitative food frequency questionnaire for the year preceding the study. The food intake recorded on the original questionnaire was changed to values in grams using "Manual for Household Measures" and then converted to corresponding amounts of nutrient ingredients by the "Nutritionist 3" program. Data analysis was performed by the SPSS soft ware package. We calculated means and standard deviations for intake levels and applied t tests to compare the results with reference values.Results: Women with MS took excessive amounts of vitamin A and vitamin C, while their daily intake of foliate, vitamin E, vitamin D, magnesium, iron, zinc, iodine and calcium was below reference values. Male patients had higher-than-recommended intake of vitamin A, phosphorous, manganese and iron. Their ingestion of foliate, Vitamin D and E, magnesium, zinc, calcium and selenium was shown to be below the recommended amount.Conclusions: In view of these results, higher intake of vitamin D and calcium is recommended. Women should be encouraged to take more iron and foliate as many symptoms of anemia mimics MS symptoms. Considering the well-known role of oxidative stress in the pathogenesis of MS, men should be urged to increase their ingestion of antioxidant-rich foods. It appears that nutritional assessment, dietary counseling and education are necessary for Iranian MS patients.

Background & Objectives: Typhoid fever has been endemic in Iran throughout its history. This Study was conducted in response to the rising number of cases reported from Rasht (capital of Gilan province in northern Iran).Methods: we performed a descriptive study on 2031 suspected cases referred to city's diagnostic laboratories in 2002 and 2003. A "definite" diagnosis was defined as Vidal test titers rising 80-fold or more over a period of one week, or a positive bacteriologic test. We completed questionnaires for the definite cases, and used the EPIINFO computer package to analyze the data.Results: The serologic prevalence was 3.94%, and 25% of the seropositive individuals had positive bacterial cultures. The geometric mean of the reciprocal titers (GMRT) was 1: 180. The prevalence was the same in both sexes and among all age groups. Factors showing a statistically significant relationship with prevalence include occupation (the greatest frequency was seen in housewives), education level, place of residence, and source of drinking water.Conclusions: We conclude that high prevalence rates coupled with the ecological conditions in this area could favor the occurrence of salmonellas outbreaks: the issue requires more extensive research for further clarification.

Background and objectives: There is growing interest in assessing gene-environment interaction in the course of case-control studies. Difficulties related to the sampling of controls have led to the development of a range of non-traditional methods that do not require controls for estimating gene-environment interaction. One of these new modalities is the case-only approach, in which the assessment of gene-environment interaction is based on information from the cases only. The present article describes the application of this approach to data from breast cancer patients and compares its efficacy with that of a traditional case-control analysis.Methods: We used age at first pregnancy, number of live birth, menopause and the total number of postmenopausal years as the "environment" factors and family history of breast cancer as the "gene" factor. We computed standard errors, 95% confidence intervals and (-2 log likelihood) to compare efficiency between case control and case-only analyses. Results: We observed significant interaction between menopause and family history of breast cancer by both methods (OR=4.32 Cl: 1.10-16.90 for case-control analysis & OR=3.40 Cl: 1.17-9.87 for case-only analysis). There was also a significant interaction effect between total years after menopause and family history of breast cancer (OR=1.07 Cl: 0.98-1.16 in case-control analysis & OR=1.07 Cl: 1.01-1.12 in case-only analysis).The case-only approach yielded narrower confidence intervals for the odds ratio, and the (-2 log likelihood) values computed by this method were correspondingly smaller.Conclusions: Comparison of confidence intervals and (-2 log likelihood) values shows that the estimation of gene environment interaction in breast cancer would be more efficient with the case-only approach than with the traditional case-control analysis.

The term "health inequalities" is not a descriptive one: it refers to discrepancies in morbidity and mortality, life expectancy, disability life adjusted years, etc that are due to differences in such factors as socioeconomic status, gender and race/ethnicity. Socio-economic inequalities are the differences in health status (e.g. disease prevalence and incidence rates) across various socio-economic groups.In Europe, measuring socio-economic health inequalities has long been a major research topic. However, there have been relatively few experimental studies in Asia, especially in developing countries. In the social context, measurement of socio-economic status is based on income, educational level and employment status. Stratifying the socio-economic groups based on a hierarchy identifies the pattern of morbidity and mortality in each socioeconomic stratum. It also shows the exact relationship between socio-economic status and health.The main data sources for determination of population health status and measuring health inequalities are registries and cross-sectional surveys. It seems that monitoring, prevention and evaluation of health inequalities, especially with a focus on socio-economic level has been neglected in developing countries, including Iron. Due to the lock of formal registries on population health status in these countries, designing cross-sectional and population-based studies would be a useful approach in the prevention and monitoring of health inequalities.