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Background Birth spacing, especially the first birth interval (FBI), is a suitable index to investigate the delayed fertil- ity that results in a low fertility pattern. Non-parametric familiar alternatives to the Cox proportional hazard regression (CPH) model include survival trees that can automatically discover certain types of covariate interactions according to the survival length. The aim of this research is to study FBI influential factors by applying survival trees. Materials and Methods In this cross-sectional study, 610 married women (aged 15-49 years), were selected from different regions of Tehran, Iran in the Winter and Spring of 2017. Classification and regression trees (CART) for the FBI survival tree were fitted by taking into consideration the predictors of each woman’s age, age at first marriage, educational level, partner’s educational level, activity, region, house ownership, kinship, partner’s race, marriage time attitude, and expenditure using R packages. Results Since the PH assumption of the CPH model was not confirmed for the covariates of age at first marriage (P=0.001), kinship (P=0.000), partner’s race (P=0.001), and marriage time attitude (P=0.042), the results of this model were not valid. Thus, a CART survival tree was fitted. The validity of the fitted model in assessing FBI was confirmed by the significant result of the log rank test (P

Background: Socio-economic factors, in addition to value and attitude changes, have had a major impact on fertility behavior of women toward childbearing. The main purpose of this study is to investigate childbearing desire of 6183 women in provinces with total fertility rate (TFR) lower (TFR ≤ 2) and upper (TFR > 2) than replacement level by classification and regression trees (CART) algorithm, as one of the most applicable classification trees. Method: In this study women’s job, place of residence, age, opinion, marriage age, educational level, and children ever born were investigated as predictors. The accuracy of fitted classification trees for CD in provinces with TFR ≤ 2 and TFR > 2 were 0.68 and 0.72, respectively. Results: As a result, women’s children ever born and age had significant roles on their desire to have a child in all provinces while their opinion toward childbearing had just effect on provinces with TFR ≤ 2. In provinces with TFR ≤ 2, 10 - 39 years old women with 2 children and less CEB were willing to have another child. Women with 2 or less children at the age of 10 - 29 as well as women with 3 or more than 3 children at the age of 20 - 29 had a desire for more children in provinces with TFR > 2. If the women have a positive attitude toward childbearing and their age is not high, they will desire to give birth to a child until they reach the ideal number of their children. Conclusion: Thus, policies in changing their attitudes toward childbearing and creating the necessary facilities to prevent delays in marriage could be an important step in changing fertility rates.

Objective (s): In many medical and epidemiological studies, each person can experience several events one after the other sequentially under some circumstances, known as recurrence events. Broad analytical objectives of recurrent events consist of describing event process in an individual, dispersion of events from one person to another, and determination of relations between constant or time-dependent predictors with event time. So the main purpose of this article is to present and interpret advanced statistical models to analyze such events which have been proposed in recent years. Methods: In this article, variance-corrected models including AG, conditional PWP (PWP-TT and PWP-GT) and marginal WLW models for analyzing recurrent events are presented and compared with each other. Results: When the number of events for each individual are small and the risk of a reoccurrence of an event varies between different events, usually conditional PWP models are used, while marginal WLW and the time-dependent AG models are applied to determine frequency of events. Conclusion: Medical and epidemiology studies should consider various factors such as the number of events, relationship between events, the variability of the effect of factors from one event to another, the biological process, and the correlation structure of data to select the valid recurrent models.

Objective (s): First birth interval has received special attention in public health and demographic investigations due to its implication in fertility, and maternal and child health. Study of ideal first birth interval also is a very important issue since it demonstrates people’s attitude towards fertility. The aim of this study was to investigate the factors, which affect ideal first birth interval among pre- marriage youths. Methods: A sample of 12500 pre-marriage male and female youths in all provinces of Iran who visited pre-marriage counseling centers was selected. The sample selection was based on multistage stratified sampling method. Data were collected in year 2014 using a structured questionnaire. The ideal first birth interval as outcome variable was indicated by univariate survival analysis and stratified Cox model while controlling for some independent covariates. Results: Based on univariate survival analysis, age, ideal numbers of children and employment status were found to have significant effects on the mean of ideal first birth interval in all provinces. However by fitting different stratified Cox models to different groups of provinces, different covariates were found to play significant effect. Conclusion: Although there were different factors for influencing ideal first birth interval in different provinces, the differences were in the same direction. In all provinces, ideal first birth interval decreased by increase in age and university students favored longer ideal first birth interval than other participants. Risk of early childbearing for women, people who lived in rural area, had lower educational levels, had greater ideal number of children and had sex preferences were higher compared to the other groups.

Background: A set of economic and social rules and regulations as well as cultural factors influence value of children; however, this value itself could alter fertility behaviors. The present study aimed at investigating the influence of the value of children on fertility behavior through considering the impact of its attitudinal factors on childbearing desire, as one of the most important dimensions of fertility behavior. Method: A cross-sectional study was conducted on 6231 females from 31 provinces of Iran, admitted to public health and treatment centers to vaccinate their children, during year 2014. The data collection tool was a questionnaire, including three value of children dimensions, including cultural (five items), social (seven items), and economic (four items) factors, and also demographic and attitudinal questions. Results: Data were analyzed using SPSS-17 software and the factors influencing childbearing desire (CD) were examined by four SEMs for four age groups in AMOS-22. Goodness of fit models was confirmed by five fit indices. Only cultural factors had a significant direct effect on CD for 30 to 39 and 40 to 49 year-old females (P-values = 0.027, and < 0.001, respectively). Conclusions: Thus, planners and policy makers should consider changes in the cultural value of children to implement successful policies to alter the current decreasing trend of fertility rate.

Background and Objective: Discriminant analysis and logistic regression are classical methods for classifying data in several studies. However, these models do not lead in valid results due to not meeting all necessary assumptions. The purpose of this study was to classify the number of Children Ever Born (CEB) using decision tree model in order to present an efficient method to classify demographic data. Methods: In the present study, CART tree model with Gini splitting rule was fitted to classify the number of CEB in fertility behavior of at least once married 15-49 year-old women, in Semnan-2012. 405 women aged 15-49 years old comprised the survey sample. Results: Women in first and second birth cohorts who had married at an early age had 3 CEB while women who had married at an older age had 2 CEB. Women in third birth cohort who had married at an early age and were employed, had 2 CEB while unemployed women in this cohort whose type of marriages were familial and non-familial had 0 and 1 CEB respectively. Women in the third birth cohort who were married in older age had 1 CEB. Conclusion: Among important advantages of CART model are the simplicity in interpretation, using distribution-free measures, considering missing data and outliers for construction trees which has increased the usage of this method. Therefore, this method is a suitable way for classifying demographic data in comparison to other classical modeling methods in the conditions that necessary assumptions are not met.

Introduction: Epilepsy is a common neurological disorder that may last a lifetime and will requireregular medical care. To examine the factors affecting the occurrence of seizures and interictalepileptiform discharge (IED) in epileptic patients with considering the correlation between them andalso because of the lack of similar studies in this field made the necessity of performing this research.Material and Methods: Data were recorded from 97 epileptic patients referred to Shafa NeuroscienceCenter between 2007 and 2010. Data analysis was performed using shared random effect model. Softwareused for data analysis was SAS 9.2, and significance level was regarded as 0.05.Results: Among the factors of gender, seizure type, war wounded and duration of epilepsy, only twofactors had jointly statistically significant effect; Duration of epilepsy on IED (p