مجله اپیدمیولوژی ایران
سال دهم شماره 1 (پیاپی 33، بهار 1393)

The aim of this study was to assess the disease trajectory and recurrence rate of pemphigus based on the analysis of the gap time between successive recurrent events. In this regard, the most important associated factors with the risk of recurrence could be explained. This longitudinal study was performed on 112 pemphigus patients who attended the dermatology department of Imam Khomeini Hospital, Tehran, Iran, from March 2006 to January 2013. The study duration was considered from the diagnosis of the disease to December 2013. Recurrent events were analyzed based on the gap time between successive events using the multivariate time dependent frailty model. The time between two recurrent gap times was determined monthly between two successive events. Decreasing the gap times between two successive events indicates that the subsequent event after the first recurrence occurs with shorter time intervals. So, the disease trajectory represents an increase in the recurrence rate over time. Based on the results of multivariate frailty model, IgG antibody's level was the only effective factor on the recurrence hazard rate of the patients. Also, this model proved that the frailty effects were time dependent frailties. Assessing the disease trajectory and recurrence hazard rate can be achieved through analyzing the gap time between successive recurrent events. This analysis also identifies the factors that influence the risk of subsequent recurrent events.

Breast cancer is the most common cancer among women. Numerous factors are effective in the improvement of patients undergoing surgery in terms of preventing relapse or need for repeated treatment during 6 months after the surgery. This study aimed to determine the factors affecting improvement of patients undergoing surgery for breast cancer using a logistic regression model. In this study information of 150 patients were extracted from the surgical records of patients underwent surgery at the Cancer Institute of Tehran Imam Khomeini Hospital. Data were analyzed through SPSS software and using logistic regression models. Of 150 studied patients, 18 patients (12%) were not fully recovered while 132 (88%) had complete remission. The mean age of the patients was 43 ± 7.5 years, 92.8% were married, and 87.3% had children. According to the results, the odds of non recovery increased by 1.26 times with each one-year increase in age, 5.3 times with each one lymph node involvement, and 8.67 times in the case of metastasis. Other variables, such as marital status, number of children, tumor size, and location of the metastasis showed no significant relationship. The Results showed that age at diagnosis, due to its relationship with metastases and number of involved lymph nodes can be directly or indirectly affect the outcome. Therefore, increasing the women's awareness about breast cancer seems to be necessary for early diagnosis which requires planning a sufficient screening program by health policy makers of the country.

Due to the increasing tendency to measure the quality of life in recent years and the extensive quality of life questionnaires, it is important to determine the appropriate method of analyzing data derived from these studies. The aim of the present study was to introduce ordinal logistic regression models as an appropriate method for analyzing the data of quality of life. The data was derived from a cross-sectional study on quality of life survey of 938 students. For data analysis, two binary logistic regression models and ordinal logistic regression models were used and the results of these models were compared. The results of goodness of fit showed that all three models were fitted well. Based on the ordinal logistic regression models, the three variables out of the explanatory variables were statistically associated with the response while based on the binary logistic regression model, after combining two categories of response variable, only two variables were significant. Therefore, combining the categories of the response variable should be avoided as much as possible because it may lead to data loss due to ignoring some of the response categories. It is concluded that to analyze quality of life data, due to the nature of the response variable, ordinal logistic regression models are recommended considering the fewer parameter estimates and easier interpretation of the results.

The length of stay (LOS) is a useful indicator that can be used according to the objective to improve hospital care performance. The purpose of our study was to find factors affecting infants LOS in NICU at Children's Medical Center, Imam Khomeini Hospital, Tehran University of Medical Sciences, using the Cox multiple hazards regression model. This historical cohort study reviewed 369 medical records of all NICU admitted newborns at Children's Medical Center in 2009. The required data were collected through a data collection form. The Cox multiple hazards regression model was used to determine the factors affecting LOS in infants who were discharged on the physician‘s order. The median of stay in NICU was 9 days. Of 369 infants, 272 were discharged with improvement. The results of multiple Cox proportional hazards regression model showed the following factors were associated with LOS in the NICU: prematurity, referral from other hospitals, gastrointestinal diseases and infections, central venous catheterization, mechanical ventilation, and antibiotic therapy (P < 0.05). Cox proportional hazards regression model should be used when the dependent variable is time and we have censored data. Improving prenatal health care, constructing NICU in hospitals with high risk labor, reduction of preterm birth risk factors, and improving primary health-care services can help us to reduce LOS in NICU.

World Health Organization has recommended the main strategies for the prevention of road traffic injuries on some of the risk factors. This study aimed to prioritize the preventive interventions according to risk factors of road traffic injuries in Iran. The potential impact fraction (PIF) of the main strategies for prevention was analyzed from national traffic police data registry in 2011 in urban and rural roads. PIF was calculated for risk factors of road traffic injuries and joint effect at three counterfactual distributions: theoretical minimum risk level, plausible minimum risk level, and feasible minimum risk level. The priority setting of preventive intervention was performed based on contribution of each risk factor. Based on the potential impact fraction of death (PIF calculated using odds ratio of death) the priorities were as follows in order: wearing a helmet by the motorcycle passenger, wearing a helmet by motorcycle rider, and lack of speed management. Risk factors in this study were more important in urban roads and joint effects of risk factors were close to 100 percent It is strongly recommended that future interventions focus on the use of the helmet by motorcycle passengers and riders, the use of the seat belt by the passengers, and speed management. Our findings indicated that laws and legislations should be pursued more seriously. Calculation of the potential impact fraction is better than the population attributable fraction and allows for more accurate prediction of the future.

Since the human diet is a combination of different foods and that this combination will affect the body differently from when these foods are received separately, the evaluation of dietary patterns is of great importance. The primary aim of this study was to examine the association between dietary patterns during pregnancy and postpartum depression. This population-based, cross-sectional study was conducted on 771 women who attended the Ardabil's health care network. This study was carried out in a period of 4 months. In this study, systematic random sampling was used. Dietary data was collected using the Willett-format Dish-based 106 items Semi-quantitative Food Frequency Questionnaire (DS-FFQ) which was designed and validated specifically for Iranian adults. Dietary patterns were identified through exploratory factor analysis based on 34 predefined food groups. In the present study, individuals who obtained a rating of 13 or higher were considered to be suffering from postpartum depression. Logistic regression was used to estimate OR and 95% CI for postpartum depression in each quartile of patterns. In the present study, three dietary patterns were identified: mixed dietary pattern, semi-healthy dietary pattern, and fruits and vegetables dietary pattern. The last one was significantly associated with a reduced risk of postpartum depression. The findings show that a diet of fruits and vegetables during pregnancy is associated with a reduction in the risk of PPD. Additional studies are recommended to confirm these finding.

Suicide is a conscious attempt to end one’s life. Evidence suggests that nearly one million people die due to suicide worldwide each year. The aim of present study was to describe the epidemiological and demographic data of suicide victims and related factors in Fars Province. In this cross-sectional study, the demographic and epidemiological data of suicide victims in Fars Province during the 5-year period from April 2007 to March 2011 was collected by a questionnaire. Finally, the data was statistically analyzed. The victims were 934 cases. The mean and standard deviation of age for the cases was 32.12 ± 81.29 years. About 72.5% & 27.3% were men & women, respectively. The most common methods of suicide were hanging (n=472, 5.50%) for men and self burning (n=103, 16%) for women. Most of the people who committed suicide (n=411, 44%) were in the third decade of life (20 to 29 years). The most common etiology (53.5%) was unknown. Due to the high incidence of suicide in young people and unmarried individuals, authorities need to consider these groups in social planning in Fars Province.

The aim of this study was to investigate the trend of mortality of children under five years old in Kurdistan Province during 2007 to 2011.

The data of this descriptive-analytical study on deaths and births was collected from provincial deaths registry system and Civil Registration System during 2007 to 2011. The main indicators including under-five mortality, infant mortality, and neonatal mortality rate during the given period were studied. The relationship between variables was calculated using chi-square test.

The neonatal mortality rate changed from 13.5 per thousand live births in 2007 to 12.2 per thousand live births in 2011. During the same period of time, the infant mortality rate and under-five mortality rate declined from 17.1 and 20.2 to 14.9 and 17.4 per thousand live births, respectively. A significant relationship was found between gender and infant mortality. Among the major causes of mortality, prenatal diseases, especially infant diseases, were the most common cause of death in the neonatal period.

According to the results of this study, although there was a reduction in the under-five mortality rate during these years, the observed decline, especially the decline in infant mortality rate, was very slow. There are still some preventable causes of death in children which require more attention by the health system and researchers.

Migraine is the most common type of headache in children. Over 30% of patients have disabilities, so early detection and timely treatment is necessary to prevent attacks, increase learning, and prevent absenteeism. The aim of the study was to determine the prevalence of migraine in children. In this cross - sectional study with two-stage stratified random cluster sampling the International Headache Society (IHS) for migraine diagnosis and (PedMIDAS) questionnaire were completed through interviews with the students’ parents. Data was analyzed with SPSS software and chi-square test. Of 1117 children with a mean age of 41.1 ± 9 years, 551 (49.3) were female and 556 (50.7) were male of whom 185 (56.16%) had a headache and 40 (2.16%) had migraine. Most of the time, the pain started on the first day of the week with a moderate intensity. Aggravating factors were physical activity and stress, and alleviating factors were sleeping and resting. The pain was bilateral and was accompanied by nausea and vomiting. The mean number of headache attacks in the past three months was 8.85± 7.65 which lasted for a mean duration of 6.38 ± 8.02 hours with a mean interval of 24.70± 26.21days. The frequency of migraine in children by age and sex were not significantly different. More than of the children had a positive family history but were not visited by the doctor. About 79.37% of the students had first degree disability, %54.10 had second degree disability, %9.05 had third degree disability, and % 1.04 had fourth degree disability. Given the increasing prevalence of migraine with age and the risk of chronic diseases and individual and social impairment, it is important to prevent headache attacks through early identification and moderation of the aggravating factors and education of non-medical preventive methods.

Knowing the population size of rare diseases or special subpopulations like injection drug users (IDUs) is one of the most important challenges in public health and health surveillance systems but it is difficult to estimate these groups. During the last few years, new methods have been suggested to estimate hidden or hard-to-reach populations, one of which is the network scale-up method (NSUM). The NSUM itself includes measuring the personal network size and estimating the prevalence of hidden and hard-to-count populations. In this paper, we basically discussed the indirect methods of calculating the population size, and the history of NSUM and its concepts, and then addressed the estimation of hidden populations with NSUM and the applicable notes for such populations.