Publications (112) View all
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Article: The prevalence of lens opacities in Tehran: the Tehran Eye Study.
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ABSTRACT: To determine the prevalence of lens opacities and cataract surgical coverage among Tehran citizens 40 years of age and older. The Tehran Eye Study was a population-based survey, with random sampling from Tehran household clusters. Those 40 years of age and older from that survey were included in this analysis. All participants underwent full optometric, slit lamp, and fundoscopic examinations. Lens opacity was assessed after pupil dilation using the modified Lens Opacities Classification System III (LOCS III). The main indices for prevalence of cataract were any lens changes, defined as the presence of a gradable cataract in one or both eyes, and all lens changes, defined as any lens changes plus a history of cataract surgery. A total of 1434 participants were included in this analysis; 305 of which met the criteria for all lens changes resulting in an adjusted prevalence of 22.7% (CI95%: 20.2%-25.3%). The prevalence was 21.2% among men and 24.5% among women. The prevalence of any lens changes was 19.1% (CI95%: 16.6%-21.6%) and the prevalence was higher in women. The prevalence for both indices increased with age. Considering their better eyes, 39 people (2.7%) were shown to have low vision because of cataract and another 12 (0.8%) were classified as blind. Cataract has affected approximately one-fifth of the Tehran population aged 40 years and over, women more than men, and has severely affected the vision of approximately 3.5% of this population. We found that access to cataract surgery facilities was not an issue.Ophthalmic epidemiology ; 16(3):187-92. · 1.93 Impact Factor -
Article: Assessing the effect of quantitative and qualitative predictors on gastric cancer individuals survival using hierarchical artificial neural network models.
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ABSTRACT: There are numerous unanswered questions in the application of artificial neural network models for analysis of survival data. In most studies, independent variables have been studied as qualitative dichotomous variables, and results of using discrete and continuous quantitative, ordinal, or multinomial categorical predictive variables in these models are not well understood in comparison to conventional models. This study was designed and conducted to examine the application of these models in order to determine the survival of gastric cancer patients, in comparison to the Cox proportional hazards model. We studied the postoperative survival of 330 gastric cancer patients who suffered surgery at a surgical unit of the Iran Cancer Institute over a five-year period. Covariates of age, gender, history of substance abuse, cancer site, type of pathology, presence of metastasis, stage, and number of complementary treatments were entered in the models, and survival probabilities were calculated at 6, 12, 18, 24, 36, 48, and 60 months using the Cox proportional hazards and neural network models. We estimated coefficients of the Cox model and the weights in the neural network (with 3, 5, and 7 nodes in the hidden layer) in the training group, and used them to derive predictions in the study group. Predictions with these two methods were compared with those of the Kaplan-Meier product limit estimator as the gold standard. Comparisons were performed with the Friedman and Kruskal-Wallis tests. Survival probabilities at different times were determined using the Cox proportional hazards and a neural network with three nodes in the hidden layer; the ratios of standard errors with these two methods to the Kaplan-Meier method were 1.1593 and 1.0071, respectively, revealed a significant difference between Cox and Kaplan-Meier (P < 0.05) and no significant difference between Cox and the neural network, and the neural network and the standard (Kaplan-Meier), as well as better accuracy for the neural network (with 3 nodes in the hidden layer). Probabilities of survival were calculated using three neural network models with 3, 5, and 7 nodes in the hidden layer, and it has been observed that none of the predictions was significantly different from results with the Kaplan-Meier method and they appeared more comparable towards the last months (fifth year). However, we observed better accuracy using the neural network with 5 nodes in the hidden layer. Using the Cox proportional hazards and a neural network with 3 nodes in the hidden layer, we found enhanced accuracy with the neural network model. Neural networks can provide more accurate predictions for survival probabilities compared to the Cox proportional hazards mode, especially now that advances in computer sciences have eliminated limitations associated with complex computations. It is not recommended in order to adding too many hidden layer nodes because sample size related effects can reduce the accuracy. We recommend increasing the number of nodes to a point that increased accuracy continues (decrease in mean standard error), however increasing nodes should cease when a change in this trend is observed.Iranian Red Crescent medical journal. 01/2013; 15(1):42-8. -
Article: Effect of a school-based oral health-education program on Iranian children: results from a group randomized trial.
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ABSTRACT: Parents and school staff play important roles in promoting children's oral health. Our study goals were to investigate whether an intervention targeting parents and school staff can improve the oral-health behavior and oral-health status of schoolchildren. Three-hundred and ninety-two schoolchildren in six schools in Tehran participated in a group randomized trial from September 2010 to March 2011. Schools were randomly allocated into three groups: comprehensive, student, and control. Intervention in the comprehensive group consisted of strategies to encourage children, their parents, and school staff to increase the frequency of toothbrushing and flossing. In the student group, the intervention targeted only children. The control group received no intervention. The primary outcome was change in oral-health behaviors (brushing and flossing), while the secondary outcomes were changes in oral hygiene and Community Periodontal indices and in Health Belief Model components. Multilevel modeling was employed for data analyses. Students who were in the comprehensive intervention group brushed and flossed significantly more frequently compared with those in the student intervention group. Although students' gingival health improved significantly in the comprehensive intervention group, such significant improvement was not seen in the student group. In conclusion, promising results are seen when the oral-health education targets both school and home settings.European Journal Of Oral Sciences 10/2012; 120(5):429-37. · 1.88 Impact Factor -
Article: Analysis of familial aggregation in total, against-the-rule, with-the-rule, and oblique astigmatism by conditional and marginal models in the tehran eye study.
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ABSTRACT: The purpose was to determine the familial aggregation of the total, against-the-rule (ATR), with-the-rule (WTR), and oblique astigmatism by conditional and marginal models in the Tehran Eye Study. Total, ATR, WTR, and oblique astigmatism were studied in 3806 participants older than 5 years from August 2002 to December 2002 in the Tehran Eye Study. Astigmatism was defined as a cylinder worse than or equal to -0.5 D. WTR astigmatism was defined as 0 ± 19°, ATR astigmatism was defined as 90 ± 19°, and oblique when the axes were 20-70° and 110-160°. The familial aggregation was investigated with a conditional model (quadratic exponential) and marginal model (alternating logistic regression) after controlling for confounders. Using the conditional model, the conditional familial aggregation odds ratios (OR) (95% confidence interval) for the total, WTR, ATRs, and oblique astigmatism were 1.49 (1.43-1.72), 1.91 (1.65-2.20), 2.00 (1.70-2.30), and 1.86 (1.37-2.54), respectively. In the marginal model, the marginal OR of the parent-offspring and sib-sib in the total astigmatism were 1.35 (1.13-1.63) and 1.54 (1.13-2.11), respectively; WTR 1.53 (1.06-2.20) and 1.94 (1.21-3.13) and; ATR 2.13 (1.01-4.50) and 2.23 (1.52-3.30). The model was statistically significant in sib-sib relationship only for oblique astigmatism with OR of 3.00 (1.25-7.20). The results indicate familial aggregation of astigmatism in the population in Tehran adjusted for age, gender, cataract, duration of education, and body mass index, so that the addition of a new family member affected with astigmatism, as well as having a sibling or parents with astigmatism, significantly increases the odds of exposure to the disease for all four phenotypes. This aggregation can be due to genetic and/or environmental factors. Dividing astigmatism into three phenotypes increased the odds ratios.Middle East African journal of ophthalmology 10/2012; 19(4):397-401. -
Article: Accuracy of HIV-Related Risk Behaviors Reported by Female Sex Workers, Iran: A Method to Quantify Measurement Bias in Marginalized Populations.
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ABSTRACT: We quantified discrepancies in reported behaviors of female sex workers (FSW) by comparing 63 face-to-face interviews (FTFI) to in-depth interviews (IDI), with corroboration of the directions and magnitudes of reporting by a panel of psychologists who work with FSW. Sensitivities, specificities, positive and negative predictive values (PPV and NPV) were assessed for FTFI responses using IDI as a "gold standard". Sensitivities were lowest in reporting symptoms of sexually transmitted infections (63.9 %), finding sex partners in venues (52.4 %) and not receiving HIV test results (66.7 %). Specificities (all >83 %) and PPVs (all >74.0 %) were higher than NPV. FSW significantly under-reported number of clients, sexual contacts and non-condom use sex acts with clients and number of days engaging in sex work in the preceding week. This study provides a quantified gauge of reporting biases in FSW behaviors. Such estimates and methods help better understand true HIV risk in marginalized populations and calibrate survey estimates accordingly.AIDS and Behavior 09/2012; · 3.49 Impact Factor
