Is obesity contagious? Social networks vs. environmental factors in the obesity epidemic

Obesity contagion among classmates: Children's relation with each other regarding weight status, physical activity, and dietary intake

A series of influential articles suggests that obesity may spread between couples, siblings, and close friends via an obesity contagion phenomenon. Classmates, as important structural equivalents in one's social network, may experience obesity contagion. However, this has rarely been examined. Anthropometric measurements, questionnaire surveys, and geographic information were collected from 3670 children from 26 schools in Northeast China. We found that classmates were positively related in terms of body mass index (BMI), body fat, physical activity, and intake of vegetables, fruits, fast food, snacks, and sugar-sweetened beverages. One standard deviation (SD) increase in classmates' mean BMI and percentage body fat was associated with 0.19 SD higher individual BMI (95% confidence interval [CI]: 0.00, 0.39) and 0.31 SD higher percentage body fat (95% CI: 0.13, 0.48). Coefficients ranged from 0.48 to 0.76 in models for physical activity, and the dietary intake of vegetables, fruit, fast food, snacks, and sugar-sweetened beverages. Children's BMI and body fat were more strongly associated with the maximum and minimum body fat levels of their same-sex classmates than with those of their general classmates. Their dietary intake and physical activity were more strongly associated with the mean/median levels of their general classmates than with those of their same-sex classmates. This study suggests that children's BMI, body fat, physical activity, and dietary intake may be related to those of their classmates. Modeling healthy behaviors in the classroom may help children develop habits that support achieving and maintaining a healthy weight. Future interventions should consider the inclusion of classmates as a social network strategy for obesity prevention.

Peer effects in weight-related behaviours of young people: A systematic literature review

Individual preferences and beliefs are perpetually shaped by environmental influences, with peers playing a key role in this dynamic process. Compelling evidence from qualitative and quantitative studies has highlighted the significant impact of peer influence on health-related decisions. This systematic literature review critically synthesises findings from 45 studies published between 2011 and 2022, providing a comprehensive understanding of the nature of peer effects on dietary, physical activity and sleep behaviours during youth. The majority of studies indicated that social norms drive directional changes in eating and physical activity. Yet, our analysis revealed a notable gap in exploring alternative mechanisms, including social comparison and social identity, despite their potential relevance. Studies, generally classified as moderate to high quality, predominantly relied on self-reported data, potentially affecting the validity and reliability of measures. Meta-regression analyses suggest a small, but significant association of sample size with the magnitude, sign and significance of the reported peer effects. Moreover, studies focusing on physical activity are more likely to report significant outcomes, whereas findings on peer influence on sleep-related studies tend to reveal less pronounced effects, compared to studies on dietary behaviours. Experimental designs do not appear to increase the likelihood of finding significant effects when compared to other study designs. In conclusion, this synthesis emphasises the need for further research into the underlying mechanisms on peer effects to better inform policy-makers in designing effective policies for improving weight-related behaviours in young people.

Assortative mixing of opinions about COVID-19 vaccination in personal networks

Many countries worldwide had difficulties reaching a sufficiently high vaccination uptake during the COVID-19 pandemic. Given this context, we collected data from a panel of 30,000 individuals, which were representative of the population of Romania (a country in Eastern Europe with a low 42.6% vaccination rate) to determine whether people are more likely to be connected to peers displaying similar opinions about COVID-19 vaccination. We extracted 443 personal networks, amounting to 4430 alters. We estimated multilevel logistic regression models with random-ego-level intercepts to predict individual opinions about COVID-19 vaccination. Our evidence indicates positive opinions about the COVID-19 vaccination cluster. Namely, the likelihood of having a positive opinion about COVID-19 vaccination increases when peers have, on average, a more positive attitude than the rest of the nodes in the network (OR 1.31, p < 0.001). We also found that individuals with higher education and age are more likely to hold a positive opinion about COVID-19 vaccination. With the given empirical data, our study cannot reveal whether this assortative mixing of opinions is due to social influence or social selection. However, it may nevertheless have implications for public health interventions, especially in countries that strive to reach higher uptake rates. Understanding opinions about vaccination can act as an early warning system for potential outbreaks, inform predictions about vaccination uptake, or help supply chain management for vaccine distribution.

Adolescent relational behaviour and the obesity pandemic: A descriptive study applying social network analysis and machine learning techniques

AIM

To study the existence of subgroups by exploring the similarities between the attributes of the nodes of the groups, in relation to diet and gender and, to analyse the connectivity between groups based on aspects of similarities between them through SNA and artificial intelligence techniques.

METHODS

235 students from 5 different educational centres participate in this study between March and December 2015. Data analysis carried out is divided into two blocks: social network analysis and unsupervised machine learning techniques. As for the social network analysis, the Girvan-Newman technique was applied to find the best number of cohesive groups within each of the friendship networks of the different classes analysed.

RESULTS

After applying Girvan-Newman in the three classes, the best division into clusters was respectively 2 for classroom A, 7 for classroom B and 6 for classroom C. There are significant differences between the groups and the gender and diet variables. After applying K-means using population diet as an input variable, a K-means clustering of 2 clusters for class A, 3 clusters for class B and 3 clusters for class C is obtained.

CONCLUSION

Adolescents form subgroups within their classrooms. Subgroup cohesion is defined by the fact that nodes share similarities in aspects that influence obesity, they share attributes related to food quality and gender. The concept of homophily, related to SNA, justifies our results. Artificial intelligence techniques together with the application of the Girvan-Newman provide robustness to the structural analysis of similarities and cohesion between subgroups.

Association of Place With Adolescent Obesity

Importance

Despite strong evidence linking place and obesity risk, the extent to which this link is causal or reflects sorting into places is unclear.

Objective

To examine the association of place with adolescents' obesity and explore potential causal pathways, such as shared environments and social contagion.

Design, Setting, and Participants

This natural experiment study used the periodic reassignment of US military servicemembers to installations as a source of exogenous variation in exposure to difference places to estimate the association between place and obesity risk. The study analyzed data from the Military Teenagers Environments, Exercise, and Nutrition Study, a cohort of adolescents in military families recruited from 2013 through 2014 from 12 large military installations in the US and followed up until 2018. Individual fixed-effects models were estimated that examined whether adolescents' exposure to increasingly obesogenic places over time was associated with increases in body mass index (BMI) and probability of overweight or obesity. These data were analyzed from October 15, 2021, through March 10, 2023.

Exposure

Adult obesity rate in military parent's assigned installation county was used as a summary measure of all place-specific obesogenic influences.

Main Outcomes and Measures

Outcomes were BMI, overweight or obesity (BMI in the 85th percentile or higher), and obesity (BMI in the 95th percentile or higher). Time at installation residence and off installation residence were moderators capturing the degree of exposure to the county. County-level measures of food access, physical activity opportunities, and socioeconomic characteristics captured shared environments.

Results

A cohort of 970 adolescents had a baseline mean age of 13.7 years and 512 were male (52.8%). A 5 percentage point-increase over time in the county obesity rate was associated with a 0.19 increase in adolescents' BMI (95% CI, 0.02-0.37) and a 0.02-unit increase in their probability of obesity (95% CI, 0-0.04). Shared environments did not explain these associations. These associations were stronger for adolescents with time at installation of 2 years or longer vs less than 2 years for BMI (0.359 vs. 0.046; P value for difference in association = .02) and for probability of overweight or obesity (0.058 vs. 0.007; P value for difference association = .02), and for adolescents who lived off installation vs on installation for BMI (0.414 vs. -0.025; P value for association = .01) and for probability of obesity (0.033 vs. -0.007; P value for association = .02).

Conclusion and Relevance

In this study, the link between place and adolescents' obesity risk is not explained by selection or shared environments. The study findings suggest social contagion as a potential causal pathway.

Social Network, Food Patterns, Physical Activity and Associations with Overweight and Obesity in Adolescents from a School in Rural Brazil

The objective of this study was to evaluate the social network, food patterns, physical activity, and their associations with overweight/obesity in adolescents from a school in rural Brazil. Students from a rural school in Northeast Brazil (n = 90) completed questionnaires on sociodemographic characteristics, food consumption, physical activity, and a name generator. Social networks were constructed using students' social proximity ties. Principal component analysis was performed to determine food patterns, and logistic models were used to investigate variables associated with overweight/obesity. Most participants were girls (62.9%), and the proportion of overweight/obesity was 30% among adolescents. Students cited 2070 people from their networks (family, friends at school, friends outside of school, and others). Among them, the family had the highest degree of influence (61%) in the network and had the most shared meals with adolescents (47%). Adolescents' perception of their family members' body size as obese, compared to normal or underweight, was prevalent (51%). Adolescents with unhealthy food patterns were 72% more likely to be categorized as overweight/obese, and eigenvector centrality was also associated with overweight/obesity (OR = 5.88, 95% CI = 1.08-32.03). Adolescents presented a social network with strong family influence, in which a high percentage of overweight/obesity was observed. Adolescents with high eigenvector centrality were more likely to be in the overweight/obesity category. Additionally, overweight/obesity was associated with unhealthy food patterns in the family network.

Resolving the Ethical Tension Between Creating a Civil Environment and Facilitating Free Expression Online: Comment Reordering as an Alternative to Comment Moderation

Incivility in online commenting sections can create a hostile environment and result in the silencing of vulnerable voices. Accordingly, content websites and social media platforms have an ethical responsibility-one that aligns with their strategic interests-to minimize users' exposure to uncivil content. To this end, platforms invest great effort and budget in automatic and manual filtering mechanisms. Yet, these efforts create a competing ethical quandary, as they often come at the expense of free expression, particularly in cases where comments do not explicitly infringe on stated guidelines but might nevertheless be interpreted as offensive. In this paper, we examine an alternative moderation approach, based on comment reordering as opposed to deletion of uncivil comments. Specifically, we show that exposure to uncivil (vs. civil) comments located in the head or at the bottom of a list of comments increases subsequent commenters' likelihood of posting uncivil comments themselves. Exposure to uncivil comments in the middle of a list, however, does not significantly enhance commenters' likelihood of commenting uncivilly. These results offer new theoretical insight into how incivility is transferred between users in online environments. Our results also suggest a straightforward technological solution for mitigating online incivility, which is more ethical and practical than current industry standards. This involves placing civil comments at the beginning and end of the comment thread, with uncivil comments located in the middle.

Genetic nurture in educational attainment

Health is strongly and positively correlated with education, which is one of many reasons to better understand the determinants of education. In this paper, we test for a specific type of family influence on education: genetic nurture. Specifically, we test whether a person's educational attainment is correlated with their sibling's polygenic score (PGS) for education, controlling for their own PGS. Models estimated using data from the National Longitudinal Survey of Adolescent to Adult Health (Add Health) yield strong evidence of genetic nurture; a two-standard deviation increase in a sibling's genetic predisposition to higher education is associated with a 13.6% point increase in the probability that the respondent has a college degree. Evidence of genetic nurture is robust to alternative measures of educational attainment and different measures of the polygenic score. An exploration of mechanisms suggests that omission of parental PGS explains no more than half of the estimated effect, and that the magnitude of the genetic nurture varies with the characteristics of the sibling.

The effect of obesity on chronic diseases in USA: a flexible copula approach

We analyze the effect of obesity on the incidence of hypertension, hyperlipidemia and diabetes in USA using a health production theoretical framework along with a bivariate flexible semi-parametric recursive copula model that account for endogeneity. In this approach, the effects of control variables are flexibly determined using additive predictors that allow for a variety of effects. Our findings suggest that there exist a positive and significant effect of obesity on the prevalence of all chronic diseases examined. In particular, after endogeneity is accounted for, the probability of having hypertension, hyperlipidemia and diabetes for obese individuals are, respectively, 35%, 28% and 11% higher than those under the obesity threshold. These findings suggest that lowering obesity rates could lead to significant reductions in the morbidity and mortality associated with these diseases.

Causal Inference for Social Network Data

We describe semiparametric estimation and inference for causal effects using observational data from a single social network. Our asymptotic results are the first to allow for dependence of each observation on a growing number of other units as sample size increases. In addition, while previous methods have implicitly permitted only one of two possible sources of dependence among social network observations, we allow for both dependence due to transmission of information across network ties and for dependence due to latent similarities among nodes sharing ties. We propose new causal effects that are specifically of interest in social network settings, such as interventions on network ties and network structure. We use our methods to reanalyze an influential and controversial study that estimated causal peer effects of obesity using social network data from the Framingham Heart Study; after accounting for network structure we find no evidence for causal peer effects.

The influence of social relationships and activities on the health of adults with obesity: A qualitative study

Background

Obesity in adults is a leading health challenge that causes millions of deaths worldwide and represents a risk factor for developing long‐term conditions. Social relationships are one of the multiple drivers shaping obesity and obesity‐related practices. However, there is still little evidence as to the processes by which relationships influence the adoption of positive and negative obesity health‐related practices—eating, physical activity and alcohol intake. This study aims first to identify the types of relationships relevant to the adoption of practices in adults with obesity and, second, to explore the type of activities these relationships engage with or promote to produce those practices and their potential health consequences.

Methods

Nineteen adults who have or had a history of obesity living in the United Kingdom were interviewed between May 2020 and March 2021. Experiences were explored through semi‐structured interviews and network mapping via videoconferencing. Data were analysed using a hermeneutic phenomenology informed thematic analysis.

Results

Three main themes were identified: (1) everyday familial routines matter, (2) chasing healthier lifestyles: comparing, modelling and connecting emotionally with friends and (3) healthcare professionals as negative influencers.

Discussion and Conclusions

Findings show how different types of relationships might shape the risk of developing and losing weight. They uncover the power of informal networks (family and friends) and highlight the potentially negative impact of formal ones (healthcare professionals). Our exploration could add to arguments about the need for stakeholders confronting obesity to be aware of the relevance of everyday social relationships in health and well‐being strategies for tackling the issue, in creating collective and individual person‐centred long‐term sustainable actions.

Patient and Public Contribution

Feedback on the tone/content of the interview questions was provided by the two first participants. The results were checked and received feedback from one of the interviewees.

Key links in network interactions: Assessing route-specific travel restrictions in China during the Covid-19 pandemic

We consider a model of network interactions where the outcome of a unit depends on the outcomes of the connected units. We determine the key network link, i.e., the network link whose removal results in the largest reduction in the aggregate outcomes, and examine a measure that quantifies the contribution of a network link to the aggregate outcomes. We provide an example examining the spread of Covid-19 in China. Travel restrictions were imposed to limit the spread of infectious diseases. As uniform restrictions can be inefficient and incur unnecessarily high costs, we examine the design of restrictions that target specific travel routes. Our approach may be generalized to multiple countries to guide policies during epidemics ranging from ex ante route-specific travel restrictions to ex post health measures based on travel histories, and from the initial travel restrictions to the phased reopening.

Forecasting Obesity and Type 2 Diabetes Incidence and Burden: The ViLA-Obesity Simulation Model

Background

Obesity is a major public health problem affecting millions of Americans and is considered one of the most potent risk factors for type 2 diabetes. Assessing future disease burden is important for informing policy-decision making for population health and healthcare.

Objective

The aim of this study was to develop a computer model of a cohort of children born in Los Angeles County to study the life course incidence and trends of obesity and its effect on type 2 diabetes mellitus.

Methods

We built the Virtual Los Angeles cohort—ViLA, an agent-based model calibrated to the population of Los Angeles County. In particular, we developed the ViLA-Obesity model, a simulation suite within our ViLA platform that integrated trends in the causes and consequences of obesity, focusing on diabetes as a key obesity consequence during the life course. Each agent within the model exhibited obesity- and diabetes-related healthy and unhealthy behaviors such as sugar-sweetened beverage consumption, physical activity, fast-food consumption, fresh fruits, and vegetable consumption. In addition, agents could gain or lose weight and develop type 2 diabetes mellitus with a certain probability dependent on the agent's socio-demographics, past behaviors and past weight or type 2 diabetes status. We simulated 98,230 inhabitants from birth to age 65 years, living in 235 neighborhoods.

Results

The age-specific incidence of obesity generally increased from 10 to 30% across the life span with two notable peaks at age 6–12 and 30–39 years, while that of type 2 diabetes mellitus generally increased from <2% at age 18–24 to reach a peak of 25% at age 40–49. The 16-year risks of obesity were 32.1% (95% CI: 31.8%, 32.4%) for children aged 2–17 and 81% (95% CI: 80.8%, 81.3%) for adults aged 18–65. The 48-year risk of type 2 diabetes mellitus was 53.4% (95% CI: 53.1%, 53.7%) for adults aged 18–65.

Conclusion

This ViLA-Obesity model provides an insight into the future burden of obesity and type 2 diabetes mellitus in Los Angeles County, one of the most diverse places in the United States. It serves as a platform for conducting experiments for informing evidence-based policy-making.

Indirect Genetic Effects of ADIPOQ Variants on Lipid Levels in a Sibling Study of a Rural Chinese Population

Variations in lipid levels are the result of combinations of genetic and environmental factors. We aim to investigate the indirect effect between siblings of the three polymorphisms of ADIPOQ on serum lipid levels in rural Chinese populations. A total of 2571 sibling pairs were enrolled as study participants. A generalized estimating equation was used to accommodate a family-based design. We used stratified analysis to detect sex combination differences in the indirect genetic effect. We found a significant association between the number of altered risk alleles of rs182052 and ego lipid levels of TG (β = 0.177, P = 0.003), TC (β = 0.140, P = 0.004) and LDL-C (β = 0.098, P = 0.014). Ego and altered genotypes of rs182052 demonstrated a joint effect on ego lipid levels of TC (β = 0.212, P = 0.019), HDL-C (β = 0.099, P = 0.002) and LDL-C (β = 0.177, P = 0.013) in recessive inheritance mode. In opposite-sex siblings, the altered GG genotype of rs182052 increased the ego lipid levels. Thus, our findings demonstrate that ADIPOQ has an indirect genetic effect on lipid levels in sibling pairs, and there are sex-combination differences in the indirect genetic effect in siblings.

Why Re-Invent the Wheel? Social Network Approaches Can Be Used to Mitigate SARS-CoV-2 Related Disparities in Latinx Seasonal Farmworkers

Latinx seasonal farmworkers are essential workers and are at elevated risk for SARS-CoV-2 in the United States. Risk factors for SARS-CoV-2 are unique to this population and include crowded living conditions, isolated social networks, and exploitative working environments. The circumstances and cultural values of Latinx seasonal farmworkers pose a unique challenge to public health authorities working to contain the spread of SARS-CoV-2. This community is in dire need of urgent public health research to identify opportunities to prevent SARS-CoV-2 transmission: social network methods could be the solution. Using previously collected and new information provided by a team of experts, this commentary provides a brief description of Latinx seasonal farmworker disparities that affect tracking and treating SARS-CoV-2 in this important group, the challenges introduced by SARS-CoV-2, and how social network approaches learned from other infectious disease prevention strategies can address these disparities.

The social contagion of temporal discounting in small social networks

Decisions often require a tradeoff between immediate and long-term gratification. How individuals resolve such tradeoffs reflects constructs such as temporal discounting, the degree that individuals devalue delayed rewards. Recent research has started to focus on temporal decisions made in collaborative contexts (e.g., dyads, small groups). Results suggest that directly interacting with others leads to revisions in preferences, such that decision makers become more similar to their collaborative partners over time (e.g., more patient following collaboration with a patient other). What remains to be seen is whether this social influence extends to indirect social effects, such as when an individual influences another’s preferences through a shared collaborative partner. In the current study, the focus was on decisions regarding hypothetical monetary rewards. Groups of three participated in a collaborative decision-making chain, in which network member X collaborated with member Y, who then subsequently collaborated with member Z. Though network members X and Z never directly interacted, a significant indirect link was observed between member X’s pre-collaborative decision preferences and member Z’s post-collaborative decision preferences. These results demonstrate that temporal decision preferences can be transmitted through intervening connections in a small social network (i.e., social contagion), showing that indirect social influence can be empirically observed and measured in controlled environments.

High school students’ friendship network, physical activity and residential locations – a stochastic actor based model

Evidence shows that adolescents do not do enough physical activity (PA), which could contribute to childhood overweight and obesity. Studies have shown that both the built environment and social networks could influence adolescents’ PA, but more studies are needed to investigate their combined influence using longitudinal data. We used a stochastic actor-based model analyzing two waves of Add Health data to test if (1) home location has a significant influence on high school student’s friendships, and (2) the neighborhood built environment has a significant influence on high school student’s PA while controlling for friendship networks. The results indicate that students’ PA level emulated peers’ PA levels and students who lived closer together, increased the likelihood of forming friendships. However, the built environment variables that described adolescents’ residential neighborhoods did not show a significant influence on students’ PA dynamics. This study contributes to our understanding of the joint impacts of social networks and home location on adolescents’ friend networks and PA dynamics in urban settings.

The influence of endogenous behaviors among social pairs: Social interaction effects of smoking

We model the observed smoking outcomes of an individual and her social contact - a spouse, friend, sibling, parent or adult child - as a simultaneous move game with complete information. We allow an individual's smoking behavior to depend on her previous behavior and carefully account for observed and unobserved heterogeneity. Our econometric model addresses simultaneity, homophily, health endogeneity, non-random attrition, and multiplicity of equilibria together. Using network data from the Framingham Heart Study, we find smaller social interaction effects among spouses and friends than Christakis and Fowler (2008) who pioneered such exploration with these data. We also find that social interaction impacts of the endogenous behaviors of siblings or a parent and an adult child are not statistically significant after disentangling them from homophily. In addition, we find that the effects of social contacts' cardiovascular disease shocks on individual smoking behavior are not statistically significant.

Assortativity and Bias in Epidemiologic Studies of Contagious Outcomes: A Simulated Example in the Context of Vaccination

Assortativity is the tendency of individuals connected in a network to share traits and behaviors. Through simulations, we demonstrated the potential for bias resulting from assortativity by vaccination, where vaccinated individuals are more likely to be connected with other vaccinated individuals. We simulated outbreaks of a hypothetical infectious disease and vaccine in a randomly generated network and a contact network of university students living on campus. We varied protection of the vaccine to the individual, transmission potential of vaccinated-but-infected individuals, and assortativity by vaccination. We compared a traditional approach, which ignores the structural features of a network, with simple approaches which summarized information from the network. The traditional approach resulted in biased estimates of the unit-treatment effect when there was assortativity by vaccination. Several different approaches that included summary measures from the network reduced bias and improved confidence interval coverage. Through simulations, we showed the pitfalls of ignoring assortativity by vaccination. While our example is described in terms of vaccines, our results apply more widely to exposures for contagious outcomes. Assortativity should be considered when evaluating exposures for contagious outcomes.

Do intersecting identities structure social contexts to influence life course health? The case of school peer economic disadvantage and obesity

Scholarship linking social contextual measures to health outcomes has grown in recent decades, but the role of individuals' intersecting identities in structuring social contexts to influence health remains unclear. Building on an existing intersectionality framework, we conceptualize how this may occur through social relationships. Then, we apply this framework to analyze whether adolescent peer social contextual disadvantage influences life-course obesity heterogeneously by individual gender, race, and early-life income. We take a life course approach as adolescence is a sensitive period for both social development and adult obesity development. In our analysis, we use cohort data from the National Longitudinal Study of Adolescent to Adult Health and leverage quasi-experimental variation in adolescent peers to addresses common sources of bias in prior observational studies. We find that among Black men from lower-income households in adolescence, there is a strong negative relationship between adolescent peer economic disadvantage and adult obesity that strengthens over time. By contrast, among Black women across adolescent household income levels, we find a strong positive relationship between adolescent peer economic disadvantage and obesity that emerges as women leave high school and endures into mid-adulthood. Among non-Black women, a more modest positive relationship appears between peer disadvantage and obesity. Among non-Black men, we find no relationship. These diverging patterns suggest that the pathways through which adolescent peer economic disadvantage influences health may differ or produce differential effects based on intersecting race, gender, and socioeconomic identities. Such heterogenous effects offer new insights, and future directions, for better understanding social life-course determinants of adult health and addressing inequities.

Social network research hotspots and trends in public health: A bibliometric and visual analysis

Objectives

To understand the research landscape and identify the research hotspots and trends of the application of social network theory and analysis to public health.

Study design

A bibliometric study of publications regarding application of social network theory and analysis to public health.

Methods

Choosing 1607 articles about the application of social network theory and analysis to public health from the core collection database of Web of Science published from 1991 to 2020 as the research sample. A bibliometric and visual analysis of publication quantity and content was performed to analyze time trends, spatial distribution, cooperation networks, influential references, and keyword co-occurrence, clusters, and emergence.

Results

There is an increasing trend in the use of social network theory and analysis in the public health field, with the United States taking the lead. Research focuses include on transmission of diseases or behavior through social networks and the influence of social networks on population health at different ages. Current research frontiers primarily include the role of social networks in tracking of emerging infectious diseases like COVID-19, preventing and controlling chronic diseases, and carrying out healthy behavioral interventions.

Conclusions

This study provides a comprehensive quantitative overview of the historic development of and latest topics in the application of social network theory and analysis method to public health. More attention should be paid to the important role of social networks in tracing the emergence of serious infectious diseases like COVID-19, as well as preventing and controlling chronic diseases and intervening in health behaviors, considering the increasing challenges and opportunities presented by online social networking.

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The use of social network theory and analysis (SNT/A) in public health has grown sharply since 2007.

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The United States has taken the lead in this field of research, with some active institutions in the U.S. and the Europe.

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The transmission of diseases or behaviors within social networks is a major research focus in this interdisciplinary field.

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Research frontiers primarily include using SNT/A to track, prevent and control diseases, like COVID-19.

Effects of programs and interventions related to the social environment on childhood and adolescent obesity: A systematic search for and scoping review of natural experiments

Given the potential importance of social environment on obesity and to better understand their causal relationship amongst children and adolescents, this scoping review systematically searches for and evaluates programs and interventions using natural experiment designs. A majority of the studies assessing peer and social norm effects reported significant findings. Peer effects with nontrivial effect sizes likely have practical implications for interventions, while a strong conclusion cannot be drawn for social norm and neighborhood safety effects. Leveraging naturally occurring data might provide future research with a promising way of establishing a more robust causal inference for the topic of interest.

The role and attributes of social networks in the provision of support to women after stillbirth: experiences from Uganda

INTRODUCTION

Communities exert stigma on mothers after stillbirth despite their potential to offer social support to the grieving family. Maternal healthcare-seeking behaviors are socially reinforced rendering a social network approach vital in understanding support dynamics which when utilized can improve community response to mothers experiencing stillbirth. However, the form and direction of social support for women when in need is not clear. The study explored the role and attributes of women's social networks in the provision of support to mothers who have experienced a stillbirth in Uganda.

METHODS

An exploratory cross-sectional study design adopting a social network approach was conducted. Data collection following established procedures was conducted on a convenient sample of 17 mothers who had experienced a stillbirth six months before the study. Frequencies and bivariate analysis were conducted to determine the factors influencing the provision of social support from 293 network members elicited during the alter generation. We then performed a Poisson regression on each of the social support forms and the explanatory variables. Network structure variables were calculated using UCINET version 6 while Netdraw facilitated the visualization of networks.

RESULTS

Overall, social support was available from all network relations mentioned by the respondents. No major variations were observed between the two time periods during pregnancy and following a stillbirth. The most common support received was in form of intangible support such as emotional and information support, mainly from females who were married and from the naturally occurring networks such as family and friends. We also observed that social support followed patterns of network relational characteristics including trust, frequency of contact and alters counted on for support more likely to provide the same.

CONCLUSIONS

A great potential for social support exists within women's social networks to help address stillbirth risk factors during pregnancy and cope after experiencing the same. Alter characteristics like being female, married, and from naturally occurring networks together with relational characteristics such as trust, frequency of contact, and count on alter for support were predictors of eventual social support. Interventions aiming at addressing stillbirth risks at the community level ought to harness these network characteristics for benefits to the mothers.

The effects of relative body weight on socioemotional and schooling outcomes among female adolescents in the United States

RATIONALE

An extensive literature has shown that individuals, especially women, with higher body mass index (BMI) face a range of negative life outcomes. Most previous studies rely on absolute measures of body weight, such as BMI and obesity status, to estimate the social impact of body weight. Using absolute measures of body weight, however, is inconsistent with social-psychological theories that explain the effects of body weight because they conflate the social effects of body weight with biological processes of body weight.

OBJECTIVE

This study extends the literature by utilizing a relative measure of body weight, or a student's BMI rank within her relevant peer group, to examine the impact of body weight on youth outcomes.

METHODS

Using data from the National Longitudinal Study of Adolescent to Adult Health and leveraging a quasi-experimental research design, this study examines the association between relative BMI and socioemotional and schooling outcomes among female adolescents in the United States.

RESULTS

Results show that female students with high relative BMI are more likely to experience a decrease in self-esteem and an increase in depressive symptoms, even after adjusting for absolute BMI and weight perceptions. These effects are partially explained by lower levels of school attachment (∼26% for self-esteem and ∼15% for depressive symptoms). This study also finds that relative BMI is associated with an increased risk of high school dropout, but not college attainment and completed years of schooling. The association between relative BMI and high school dropout is partially explained by a combination of lowered self-esteem (∼7%), increased depressive symptoms (∼12%), as well as a decline in academic achievement (∼33%) and aspirations (∼12%).

CONCLUSION

We argue that to better understand how body weight affects one' life outcomes, it is essential to take into consideration the social contexts in which one is embedded.

Is Health Contagious?-Based on Empirical Evidence From China Family Panel Studies' Data

This study empirically analysed the contagion of health using data from China Family Panel Studies. We first controlled variables related to health behaviour, medical conditions, individual characteristics, household characteristics, group characteristics, and prefecture/county characteristics and then employed multiple methods for estimation. The estimates showed that the average health level of others in the community had a significant positive effect on individual self-rated health-health was contagious. The measurement results remained robust after the endogeneity of the core explanatory variables was controlled using two-stage least squares. Furthermore, by analysing the heterogeneity of health contagion, we found that the contagion effect of health varied with the level of medical care, household affiliation, gender, rural/urban areas, and age groups. The contagion effect of health was more pronounced in the elderly population and the rural areas of the central region, where the level of medical care is relatively low, whereas it did not differ significantly between genders. Finally, the learning or imitation mechanism and social interaction mechanism of health contagion were examined.

Social network characteristics and alcohol use by ethnic origin: An ego-based network study on peer similarity, social relationships, and co-existing drinking habits among young Swedes

The study explores how social network determinants relate to the prevalence and frequency of alcohol use among peer dyads. It is studied how similar alcohol habits co-exist among persons (egos) and their peers (alters) when socio-demographic similarity (e.g., in ethnic origin), network composition and other socio-cultural aspects were considered. Data was ego-based responses derived from a Swedish national survey with a cohort of 23-year olds. The analytical sample included 7987 ego-alter pairs, which corresponds to 2071 individuals (egos). A so-called dyadic design was applied i.e., all components of the analysis refer to ego-alter pairs (dyads). Multilevel multinomial-models were used to analyse similarity in alcohol habits in relation to ego-alter similarity in ethnic background, religious beliefs, age, sex, risk-taking, educational level, closure in network, duration, and type of relationship, as well as interactions between ethnicity and central network characteristics. Ego-alter similarity in terms of ethnic origin, age and sex was associated with ego-alter similarity in alcohol use. That both ego and alters were non-religious and were members of closed networks also had an impact on similarity in alcohol habits. It was concluded that network similarity might be an explanation for the co-existence of alcohol use among members of peer networks.

An incentive-based health program using MyPlate: a pilot study analyzing college students' dietary intake behavior

Is dietary education, incentivized by financial rewards, effective in achieving improved dietary intake behavior of college students? Participants: Fifty-seven undergraduates (18-24 years old), non-nutrition major students. Methods: The intervention group participated in weekly nutrition education meetings which focused on MyPlate for four weeks. Both the control and the intervention groups completed two online surveys that assessed the students' knowledge and dietary behavior at the beginning and at the end of the 4-week education program. The respondents' diet quality was determined by their compliance with MyPlate and their Healthy Eating Index's recommendations. Results: Students who received education showed the most improvement regarding their knowledge and dietary behavior. These respondents tripled their average per capita consumption of whole grains and increased their fruit and vegetable intakes. Conclusions: Educating college students to work toward improving their diets with the assistance of incentives may have positive effect on their health behaviors.

Physiological consequences of transient hyperleptinemia during discrete developmental periods on body weight in mice

Leptin plays a role in central nervous system developmental programs and intercurrent physiological processes related to body fat regulation. The timing and neuromolecular mechanisms for these effects are relevant to the prevention and treatment of obesity. Factors implicated in a body weight "set point" including dietary fat, circulating leptin, and other adipokines tend to covary with adiposity and are difficult to disarticulate experimentally. To dissociate leptin effects from adiposity and diet, we created a transgenic mouse in which leptin expression is regulated by doxycycline exposure. Using this system, we investigated the physiological consequences of developmentally-timed transient hyperleptinemia on subsequent adiposity. We evaluated physiological effects of leptin elevation during adulthood (9 to 29 weeks old), "adolescence" (3 to 8 weeks old), and the immediate postnatal period [postnatal days 0 to 22 (P0 to P22)] on long-term adiposity and susceptibility to gain weight on high-fat diet (HFD) fed ad libitum. We found that inducing chronic hyperleptinemia in adult or "adolescent" mice did not alter body weight when excess leptin was discontinued, and upon later exposure to HFD, weight gain did not differ from controls. However, transient elevation of circulating leptin from P0 to P22 increased weight and fat gain in response to HFD, indicating greater susceptibility to obesity as adults. Thus, transient plasma leptin elevations-mimicking one aspect of transient adiposity-increased later susceptibility to diet-induced obesity, although these effects were restricted to a critical developmental (P0 to P22) time window. These findings may have clinical implications for weight management in infancy.

Peer influence on obesity: Evidence from a natural experiment of a gene-environment interaction

The role of peers in explaining the obesity epidemic is difficult to evaluate, largely due to selection (the tendency of similar individuals to make friends with each other). Our study addresses this selection issue by using data from a natural experiment of randomly assigned college roommates. We investigate whether and how peers, gender, and the FTO gene interactively influenced BMI. We find that women with a weight-prone version of the gene were about three pounds lighter if assigned frequently-exercising roommates than if assigned non-frequently-exercising roommates. However, living with frequently-exercising roommates had little impact for women without the weight-prone version of the gene or for men regardless of genotype. We find that individuals with the weight-prone version of the gene exercised more often when assigned frequently-exercising roommates. This might be a mechanism through which the effect of frequently-exercising roommates worked.

Factors That Influence Health-Promoting Self-care in Registered Nurses: Barriers and Facilitators

Nurses are instrumental in the battle against lifestyle-related diseases, yet nurses may not be participating in their own health-promoting self-care. This study used qualitative content analysis of survey responses to explore nurses' perceptions regarding barriers and facilitators to health-promoting behaviors such as exercise, healthy eating, and participation in stress reduction activities. Seven themes emerged: lack of time/overwork, lack of resources/facilities, fatigue, outside commitments, "unhealthy" food culture, supportive versus unsupportive individuals, and positive versus negative role models. Institutional, interpersonal, and intrapersonal changes are needed to adequately address barriers to nurses' participation in health-promoting behaviors.

Not only in my genes: The effects of peers' genotype on obesity

We use data from three waves of Add Health to study the short- and long-run effects of high school peers' genetic predisposition to high BMI-measured by grade-mates' average BMI polygenic scores-on adolescent and adult obesity in the U.S. We find that, in the short-run, a one standard deviation increase in peers' average BMI polygenic scores raises the probability of obesity for females by 2.8% points, about half the size of the effect induced by a one standard deviation increase in one's own polygenic score. No significant effect is found for males. In the long-run, however, the social-genetic effect fades away, while the effect of one's own genetic risk for BMI increases substantially. We suggest that mechanisms explaining the short-run effect for females include changes in nutrition habits and a distorted perception of body size.

Social Influences on Obesity: Current Knowledge, Emerging Methods, and Directions for Future Research and Practice

PURPOSE OF REVIEW

Individuals tend to be socially connected with those of similar weight and obesity status. To inform future research and intervention development, we reviewed recent literature examining social influences on weight with a focus on mechanisms of social influence, populations studied, and emerging analytical methods.

RECENT FINDINGS

Social networks appear to influence weight gain and weight loss. It remains unclear what underlying mechanisms (e.g., social norms, social comparison, behavioral modeling) drive this relationship. Stochastic actor-oriented modeling is an important method in the field, but other work has leveraged natural experiment or randomized designs to study social influence. Future networks and obesity research should examine social influence mechanisms, focus on diverse populations across the life course, and carefully consider how to adequately control for competing factors of social selection and physical environments.

Social network influences and the adoption of obesity-related behaviours in adults: a critical interpretative synthesis review

BACKGROUND

Obesity is a key risk factor for developing a long-term condition and a leading cause of mortality globally. The limited evidence associated with interventions that currently target obesity-related behaviours demand new approaches to tackle this problem. Given the evidence that social ties are implicated in the gaining and reduction of weight, the use of social networks in interventions is potentially a novel and useful means of tackling this health issue. There is a specific gap in the literature regarding what and how social network properties and processes together with environmental and individual factors influence the adoption of positive and negative obesity-related behaviours in adults.

METHODS

To address this gap in developing an integrated and holistic conceptual approach, a critical interpretative synthesis was undertaken following a line of argument synthesis as an analytical strategy.

RESULTS

Twenty-four studies were included. The data-driven themes meso-micro network processes, contextual and individual factors, and types of ties and properties were identified individually as components and causes of different health scenarios. Nevertheless, these drivers do not act on their own. As a consequence, developing multi-agent coalitions considering cross-level influences between the data-driven themes are two mechanisms that are created to understand more in-depth how social networks and the environment influence the adoption of obesity-related behaviours. These two new constructs point to a dynamic multilevel set of influences between multiple constructs, developing scenarios where positive and negative health results are identified.

CONCLUSIONS

This critical interpretative synthesis offers a new means of exploring the application of social network properties and mechanisms in the 'obesity' field. The synthesizing argument created during the analysis process might be considered by health policy-makers, who might need to contemplate the wider open system of socially connected individuals and harness these forces to design new interventions where social networks and other contextual and individual factors operate together in a complex multilevel environment influencing obesity-related behaviours and practices.

Using social network analysis to examine alcohol use among adults: A systematic review

Background

Alcohol use and abuse constitute a major public health problem and identifying their determinants is a priority. Social network analysis can indicate how characteristics of social networks are related to individual health behaviors. A growing number of studies have used social network analysis to examine how social network characteristics influence adult alcohol consumption, but this literature has never been systematically reviewed and summarized. The current paper systematically reviews empirical studies that used social network analysis to assess the influence of social network characteristics on drinking behaviors in adults.

Methods

A literature search of PubMed/MEDLINE, EMBASE, PsycINFO and Web of Science databases and a review of the reference lists of retrieved articles was conducted in March 2019. Two reviewers independently screened 5,510 non-duplicate records, and further screened the full text of 150 articles to determine their eligibility for inclusion. Seventeen articles were judged eligible and included.

Results

Most studies were conducted among young adults (mean age<30), in university settings or follow up visits with adolescent networks moving into adulthood. The objectives and methods of the included studies were heterogeneous. All included studies reported a statistically significant association between a social network characteristic and an alcohol consumption-related outcome. Social network members drinking behaviors were associated with participants’ drinking behaviors in multiple ways.

Discussion

In young adults, among whom the majority of identified studies were conducted, with whom they socialize and how they socialize appears to be associated with alcohol consumption; this was observed across methodologies and settings. We still know very little about the relationship of social networks to drinking in older age groups, and in populations most impacted by alcohol. As social networks appear to play a role in the consumption of alcohol in young adulthood, interventions that utilize social networks to help reduce harmful alcohol consumption should be considered.

Effects of the peer metagenomic environment on smoking behavior

Recent scholarship suggests that the genomes of those around us affect our own phenotypes. Much of the empirical evidence for such "metagenomic" effects comes from animal studies, where the socio-genetic environment can be easily manipulated. Among humans, it is more difficult to identify such effects given the nonrandom distribution of genes and environments. Here we leverage the as-if-random distribution of grade-mates' genomes conditional on school-level variation in a nationally representative sample. Specifically, we evaluate whether one's peers' genetic propensity to smoke affects one's own smoking behavior net of one's own genotype. Results show that peer genetic propensity to smoke has a substantial effect on an individual's smoking outcome. This is true not only when the peer group includes direct friends, and therefore where the individual plays an active role in shaping the metagenomic context but also when the peer group includes all grade-mates and thus in cases where the individual does not select the metagenomic environment. We explore these effects further and show that a small minority with high genetic risk to smoke ('bad apples') can greatly affect the smoking behavior of an entire grade. The methodology used in this paper offers a potential solution to many of the challenges inherent in estimating peer effects in nonexperimental settings and can be utilized to study a wide range of outcomes with a genetic basis. On a policy level, our results suggest that efforts to reduce adolescent smoking should take into account metagenomic effects, especially bad apples, within social networks.

Roommate effects in health outcomes

We use randomized roommate assignment in dormitories in a college in Kolkata in India to examine peer effects in weight gains among roommates. We use administrative data on weight, height, and test scores of students at the time of college admission and then survey these students at the end of their first and second years in college. We do not find any significant roommate specific peer effect in weight gain. Our results rather suggest that an obese roommate reduces the probability that the other roommates become obese in subsequent years. We examine potential mechanism using survey data on students' eating habits, smoking, exercise, and sleeping patterns. We find that obese roommates sleep longer, which in turn improves the sleep pattern of others, which might explain the weak negative effect of obese roommates on the weight of others in the same room.

Peer effects of obesity on child body composition

This study investigates whether peer obesity is a driver of individual weight changes in public school children and whether the impact of peer effects changes as children age. Quantifying peer effects is important for understanding the social determinants of obesity and for planning effective school wellness policies. However, the extant empirical research on peer effects is limited due to difficulties in separating causal influences from confounding factors. This study overcomes some of these difficulties by using a within-school, across-cohort empirical design to separate confounding factors at the individual, school and school-grade level for over one million public school children. The results show that increases a one standard deviation increase in average classmate body mass index (BMI) leads to a modest but meaningful increase of 0.395 standard deviation increase in a child's own BMI. Peer-effects are highest (0.813) for children in Kindergarten and decline with age. These findings suggest that the critical time for school-grade level intervention may be in the earliest ages of childhood development.

Social Data: Biases, Methodological Pitfalls, and Ethical Boundaries

Social data in digital form-including user-generated content, expressed or implicit relations between people, and behavioral traces-are at the core of popular applications and platforms, driving the research agenda of many researchers. The promises of social data are many, including understanding "what the world thinks" about a social issue, brand, celebrity, or other entity, as well as enabling better decision-making in a variety of fields including public policy, healthcare, and economics. Many academics and practitioners have warned against the naïve usage of social data. There are biases and inaccuracies occurring at the source of the data, but also introduced during processing. There are methodological limitations and pitfalls, as well as ethical boundaries and unexpected consequences that are often overlooked. This paper recognizes the rigor with which these issues are addressed by different researchers varies across a wide range. We identify a variety of menaces in the practices around social data use, and organize them in a framework that helps to identify them. "For your own sanity, you have to remember that not all problems can be solved. Not all problems can be solved, but all problems can be illuminated." -Ursula Franklin.

Association between environmental factors and BMI: evidence from recent immigrants from developing countries

BACKGROUND

To study the association between the surrounding local environmental factors and the body mass index of immigrants in the USA.

METHODS

We use the New Immigrant Survey, to study the association of obesity prevalence in a region on body mass index. We consider local obesity rate as an outcome of the local environmental factors. Using ordinary least squares, three versions of equations are estimated to quantify the contribution of individual-level, acculturation, and environmental effects on immigrants' body mass index.

RESULTS

We find statistically significant results for the correlation of local obesity rate and body mass index. For every 1% increase in the obesity rate, the body mass index levels increase by 0.182 kg/m². Evidence also suggests dietary assimilation in immigrants is influenced by local environmental factors and that dietary change affects body mass index of female immigrants.

CONCLUSIONS

Immigrants' body mass index increase with the increase in the local obesity rate of the region where they reside.

Testing for family influences on obesity: The role of genetic nurture

A large literature has documented strong positive correlations among siblings in health, including body mass index (BMI) and obesity. This paper tests whether that is explained by a specific type of peer effect in obesity: genetic nurture. Specifically, we test whether an individual's weight is affected by the genes of their sibling, controlling for the individual's own genes. Using genetic data in Add Health, we find no credible evidence that an individual's BMI is affected by the polygenic risk score for BMI of their full sibling when controlling for the individual's own polygenic risk score for BMI. Thus, we find no evidence that the positive correlations in BMI between siblings are attributable to genetic nurture within families.

Obese Peers' Influence on Students' BMI: Heterogeneity in Race and Sex

Objectives

In this study, we investigate peer influence on obesity, with a focus on race and sex.

Methods

We conducted econometric analysis of longitudinal health data of 277,566 public school students, ages 5-13 years.

Results

A percentage point increase in the proportion of obese students within the same grade increased a student's BMI z-scores by about 4 one-thousandths of a standard deviation. On racial peers, the standard deviation increase in BMI z-score is 3.9 one-thousandths for Hispanics or Caucasians and 4.9 one-thousandths for African Americans. Influence of obese peers is nearly identical for boys and girls.

Conclusions

Such a small magnitude of obese peers' estimate suggests that classroom peers do not play a substantial role in weight gain or loss in elementary schools.

Childhood obesity in Mexico: A critical analysis of the environmental factors, behaviours and discourses contributing to the epidemic

Mexico has the highest prevalence globally for children who are overweight. We conducted a qualitative study to understand childhood obesity in Mexico and the complex factors at play. Data were collected at three elementary schools in a low socio-economic area in Mexico City. Semi-structured interviews were conducted with 60 children, 24 parents and 28 teachers. The children interviewed were between the ages of 8 and 12 years old. Interview texts were analysed using NVivo 9 and 10 and thematic discourse analysis was used. Findings revealed how children’s choices around nutrition and physical activity were constrained by their environment and discursive constructions.

Heterogeneous effects of obesity on mental health: Evidence from Mexico

Obesity can spread more easily if it is not perceived negatively. This issue may be more pronounced among the poor, a conjecture that we test in this paper. We start with general evidence on the concave relationship between income and obesity, both across countries and within Mexico, a country characterized by very unequal development levels and the highest obesity rate in the world. We suggest a general model that explains this stylized fact from a simple necessary condition, namely, the complementarity between nonfood consumption and health concerns. Then, we test the direct effect of overweight on mental health among Mexican women. We find a positive effect of obesity in the low consumption group and a depressing effect among the rich. This result is robust to the inclusion of a range of confounders (childhood conditions, lifestyle variables, food expenditure, and household shocks) and after instrumenting individual fatness by the variation in genetic predisposition. The complementarity between living standards and weight concerns may reflect different norms, different labor market penalties, or simply different returns to healthy time across the social spectrum.

Are some neighborhoods bad for your waistline? A test of neighborhood exposure effects on BMI

I study the causal impact of neighborhoods on body mass index (BMI). Through exploiting variation in the number of years individuals have lived in their neighborhood, using a data set from California, I examine if there exist causal effects of exposure to neighborhoods with high potential effects on one's BMI. The identifying assumption is that there are no unobserved individual level characteristics correlated with both BMI and moving, after controlling for observables. I find evidence that suggests that neighborhoods do not have a causal impact on BMI.

Proximity effects in obesity rates in the US: A Spatial Markov Chains approach

In this paper, we investigate, by means of a Spatial Markov Chains approach, the existence of proximity effects at State level for US data on obesity rates in the period 1990-2011. We find that proximity effects do play an important role in the spatial diffusion of obesity (the obesity 'epidemics'), and that the actual health geography of nearby States in terms of high vs. low obesity rates makes an important difference as to the future evolution of the State's own obesity rate over time. This means, in particular, that clusters of States characterized by uniformly high levels of obesity rates, as it happens for instance in the US Southern macro-region, may suffer from a perverse 'geographical lock-in' effect that calls for coordinated action across States to implement effective countervailing policies.

Childhood Obesity and Academic Outcomes in Young Adulthood

The present study used nationally representative data from the National Longitudinal Study of Adolescent Health (a.k.a., Add Health) to examine the impact of childhood obesity on young adult educational attainment. In addition to weight status, independent variables included race–ethnicity, immigrant generational status, family socio-economic status (SES), preference for overweight and obese friends in school, school socio-economic and race–ethnic composition, and other important predictors. Educational attainment was measured as a categorical variable with the categories reflecting key educational benchmarks: (1) being a high school graduate; (2) having some college education; and (3) having completed a bachelor’s or higher degree. The results indicate that in general, individuals who were obese as children are less likely to transition from high school to college, and even less likely to obtain a baccalaureate or more advanced degree. In line with the social network hypothesis of the obesity epidemic, we also found that having overweight and obese friends drives down the odds of educational success. Attendance at a higher SES school or a school with a lower percentage of minority students was positively associated with the odds of college attendance and obtaining a baccalaureate. Other important effects included race–ethnicity and immigrant generational status.