Estimating Social Network Size Using Network Scale-Up Method (NSUM) in Iranshahr, Sistan and Baluchestan Province, Iran
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Original Article http://mjiri.iums.ac.ir Medical Journal of the Islamic Republic of Iran (MJIRI) Med J Islam Repub Iran. 2020(18 Apr);34.35. https://doi.org/10.34171/mjiri.34.35 Estimating social network size using network scale-up method (NSUM) in Iranshahr, Sistan and Baluchestan Province, Iran Sakineh Narouee1, Mohsen Shatti2, Mahnaz Didevar3, Mahshid Nasehi*1 Received: 21 Jan 2018 Published: 18 Apr 2020 Abstract Background: The network scale-up method is an indirect method of estimating the size of hidden and hard-to-reach populations. An important prerequisite in this method is to estimate the size of an active social network, as considered in the present study. Methods: In 2015, the social network size was calculated using the known subpopulation approach and maximum likelihood estimation in the central, Bampur, and Bazman districts of Iranshahr province. Individuals older than 18 years took part in a street- based survey. The relationship between the demographic variables and social network size estimation was analyzed (p< 0.05). Linear regression was used to investigate the relationship of each known subpopulation with underlying variables. Data were analyzed in Excel 2010 and SPSS 19. Results: From among 1000 participants, 50.2% lived in rural areas. The social network size of the residents of Iranshahr was estimated to be 308.35 with 12 remaining subgroups. The Pearson’s correlation coefficient between the real and estimated values in known subpopulations was equal to 0.92 (p= 0.001). Men aged 25-39 years, those with high education levels, employees, and those residing in villages had a wider social network. The estimated social network size had a significant relationship with gender, education level, and place of residence (p< 0.001). Conclusion: The estimated social network size in Iranshahr was smaller than the value reported by a nationwide study (the ratio- based method). Keywords: Network scale-up, Population size estimation, Social network size, Hidden population Conflicts of Interest: None declared Funding: The present study was supported by Iran University of Medical Sciences, Tehran, Iran, with the collaboration of Iranshahr University of Medical Sciences and Health Services, Sistan and Baluchestan Province. *This work has been published under CC BY-NC-SA 1.0 license. Copyright© Iran University of Medical Sciences Cite this article as: Narouee S, Shatti M, Didevar M, Nasehi M. Estimating social network size using network scale-up method (NSUM) in Iranshahr, Sistan and Baluchestan Province, Iran. Med J Islam Repub Iran. 2020 (18 Apr);34:35. https://doi.org/10.34171/mjiri.34.35 Introduction For appropriate planning, evaluation, budget allocation, icantly reduce the reliability of responses (1, 4, 5). and HIV prevention programs, the size of hidden or hard- The network scale-up (NSU) method with an indirect to-reach populations must be estimated. Such populations approach is one of the best data collection methods of include injection drug users, female sex workers and their hidden populations. In this method, individuals are asked clients, and men who have sex with men (MSM). An es- how many people they know in their network of acquaint- Downloaded from mjiri.iums.ac.ir at 15:08 IRDT on Monday May 25th 2020 [ DOI: 10.34171/mjiri.34.35 ] sential part of health system management is the HIV care ances who have specific high-risk behaviors. The basic system (1, 2). The multiplier and capture-recapture are principle in using the NSU method is that the social net- common sampling methods which cannot provide an ac- work size describes general population features and is a curate estimation of hidden populations (3, 4). These prerequisite for calculating the hidden population size in methods are not fully functional due to the complexity of the community (1, 6). Therefore, the social network size determining those with high-risk behaviors and can signif- of individuals in target subpopulations of any study is ______________________________ Corresponding author: Dr Mahshid Nasehi, [email protected] ↑What is “already known” in this topic: 1. Department of Epidemiology, School of Public Health, Iran University of Medical Network scale-up (NSU), with an indirect approach, is one of Sciences, Tehran, Iran the best data collection methods of hidden populations. 2. Mental Health Research Center, School of Behavioral Sciences and Mental Health, Tehran Institute of Psychiatry, Iran University of Medical Sciences, Tehran, Iran →What this article adds: 3. Iranshahr University of Medical Sciences, Sistan and Balouchestan, Iran In this study, the importance of the size of a regional social network was delineated. Estimating social network size using NSUM directly associated with its real size in the general popula- ing final subpopulations. Subpopulations with impossible tion (5). accurate access to information were excluded. Therefore, The network scale-up method is used in various coun- 2 subgroups (people who went abroad or joined the mili- tries such as the USA, Ukraine, China, Japan, and Thai- tary during the last year) were excluded at the beginning land. Similar studies have also been performed for social of the study. Then, subpopulations with a relative fre- network size estimation in Brazil, Rwanda, and Moldova. quency of 0.1% to 4% of the total population of Iranshahr Calculated estimates vary from 55 to 399 and are between were selected. In this stage, 14 inappropriate subpopula- 308 and 380 in Iran. Therefore, the difference in social tions were removed. Various errors that could have affect- network size in different studies shows the importance of ed the final result were considered in calculating the social regional studies (1, 5). network size. Therefore, subpopulations that increased the Sistan and Baluchestan Province is located in Southeast possibility of probable error in the study with no proper of Iran, bordering with Afghanistan and Pakistan, which correction method were also excluded from the list of are among the largest drug producers in the world. The subpopulations. Names with more popularity among peo- city of Iranshahr in this province with specific regional, ple during the last 3 decades and an approximately even ethnic, cultural, and social features is close to the city of distribution were selected. Finally, 16 subpopulations Sarbaz. This city is located in the center of Sistan and Ba- were selected as the sample for further study. These sub- luchestan province on the path of foreigners and drug populations included first-graders, university entrance transit. Studies demonstrate that cultural and social differ- exam participants, state university students, elementary ences affect social network size (2). The present study was school employees, married people, those who had a nor- conducted to estimate the social network size of residents mal delivery or cesarean section, those with thalassemia of Iranshahr with the population of 265 316 in 2015 to major, and those with intellectual disability, and those provide a population estimate of groups such as drug users named Asieh, Abdullah, Samira, Yasser, Yasna, Matin, or in the city. To this end, the effect of different factors was Omar. examined on social network size using estimation correc- In calculating the social network size with the known tion methods. subpopulation approach and maximum likelihood estima- tion (MLE), Formula 1 was used where ĉ is the social Methods network size of the participant i, is the number of In total, 1000 people, equally composed of men and people that the person i knows from the known group j, women, participated in this cross sectional study. Women is the real population size of the known group j, and t is made up 50.2% of the population of Iranshahr. About the total number of base population in the desired area. 15.7% of the general population of the city belonged to 1. ĉ=(∑/ ∑).t 18-24 age group and 21.33% to 25-39 age group. Moreo- The estimation standard error was calculated to compute ver, 710, 250, and 40 of the participants were surveyed in the 95% confidence interval of the social network size the central, Bampur, and Bazman districts, respectively. using Formula 2. The survey was conducted with nearly equal sampling 2. SEĉ =√ĉ t/ ∑ ratios of 49.8 in urban areas and 50.2 in populated rural In the NSU method, there are 3 important assumptions areas. The study sample was selected using the street- which can respectively cause barrier effect, transmission based simple sampling method from among those who error, and estimation effect if not available: (a) partici- were alone in crowded areas such as streets, parks, hospi- pants have equal probability of knowing each member of tals, clinics, and taxi stations. The participants aged over the studied subpopulation in the study; (b) participants 18 years and had lived in Iranshahr for at least 5 years. have full knowledge of their social network; and (c) it is The questionnaires were filled out by 4 local trained in- not highly difficult for them to remember the number of quirers in Iranshahr in a face-to-face manner by respecting people in their social network and they can remember the sex-matching between the inquirer and the participant and number of social networks clearly and quickly. In differ- Downloaded from mjiri.iums.ac.ir at 15:08 IRDT on Monday May 25th 2020 [ DOI: 10.34171/mjiri.34.35 ] after explaining the research objectives and obtaining in- ent studies, various correction methods are employed to formed consent from the participants. The inquirers asked reduce the effect of the noted errors so that the accurate the participants whether they knew someone in a certain social network size can be estimated. In this study, ac- subgroup. The term “knowing” reflected the followings: quaintances who were in the respondents’ social network (1) Person A knows person B and vice versa by name and but were not residents of Iranshahr were eliminated from face; (2) they are in touch face to face, by phone, or email all estimations.