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

Do environmental factors drive obesity? Evidence from international graduate students

International students offer a unique window into the role environmental factors play in driving obesity. Naïve estimates of the relationship between environmental factors and obesity are often plagued by reverse causation, sample selection, and omitted variable bias. In this study, we survey international students at 40 public universities across the United States. We use this unique data to link the weight gain of international students to the prevalence of obesity where they live. We argue that our estimates are less likely to be biased as international students have limited control over the environment to which they are exposed upon arrival in the United States. We find that students living in areas with a higher prevalence of obesity show a biologically important and statistically significantly greater increase in weight as compared to those living in areas with a lower prevalence of obesity. Results provide cautious evidence that environmental characteristics of a region can affect the weight gain of individuals.

Social exclusion of the adolescent with overweight: study of sociocentric social networks in the classroom

BACKGROUND

Multiple studies have shown the social consequences of suffering overweight, with social exclusion or isolation as some of the most important. In order to study the social patterns among adolescents, we have set as objectives to analyse the position of the individual within their network from a sociocentric perspective, comparing the relational pattern of the adolescents suffering from overweight with those who are normal weight.

METHOD

This was a cross-sectional descriptive study using logistic regression and social network analysis. We analysed the contact patterns of 235 adolescents in 11 social networks, classifying contact into three levels of intensity: minimum, intermediate and maximum (friendship). The WHO reference was used for the variable of overweight.

RESULTS

The prevalence of overweight was 30.2% (25.5% overweight and 4.7% obesity). An analysis of the relational patterns of individuals with overweight showed that at the minimum contact level, they established fewer relationships and less closeness (odds ratio [OR]: 2.32; confidence interval [CI] 95%: 1.17-4.66; p-value: 0.016). This effect was more marked in female adolescents. At intermediate contact level, they had few relationships and low prestige (OR: 3.29; CI: 95%; 1.03-10.51; p-value: 0.045, OR: 3.18; CI: 95%; 1.00-10.04; p-value: 0.049, respectively). At maximum contact level (friendship), female adolescents related little with other adolescents (OR: 3.78; CI: 95%; 1.07-13.32; p-value: 0.038).

CONCLUSIONS

Adolescents with overweight take up peripheral positions within their social network, choosing by themselves not to establish contact with others. Social network analysis is crucial to detect adolescents with overweight at risk of exclusion and help alleviate psychological and social deficits.

Network Interventions for Changing Physical Activity Behaviour in Preadolescents

Network interventions can help achieve behavioural change by inducing peer-pressure in the network. However, inducing peer-pressure without considering the structure of the existing social network may render the intervention ineffective or weaker. In a 7-week school-based field experiment using preadolescents' physical activity (PA) as a proxy for estimating behavioural change, we test the hypothesis that boys' and girls' distinct networks are susceptible to different social incentives. We run three different social-rewards schemes, in which classmates' rewards depend on the PA of two friends either reciprocally (directly or indirectly) or collectively. Compared to a random-rewards control, social-rewards schemes had an overall significantly positive effect on PA (51.8% increase), with females being more receptive to the direct reciprocity scheme (76.4%) and males to team (collective) rewards (131.5%). Differences in the sex-specific sub-networks can explain these findings. Network interventions adapted to the network-specific characteristics may constitute a powerful tool for behavioural change.

Applications of social network analysis to obesity: a systematic review

People's health behaviours and outcomes can be profoundly shaped by the social networks they are embedded in. Based on graph theory, social network analysis is a research framework for the study of social interactions and the structure of these interactions among social actors. A literature search was conducted in PubMed and Web of Science for articles published until August 2017 that applied social network analysis to examine obesity and social networks. Eight studies (three cross-sectional and five longitudinal) conducted in the US (n = 6) and Australia (n = 2) were identified. Seven focused on adolescents' and one on adults' friendship networks. They examined structural features of these networks that were associated with obesity, including degree distribution, popularity, modularity maximization and K-clique percolation. All three cross-sectional studies that used exponential random graph models found individuals with similar body weight status and/or weight-related behaviour were more likely to share a network tie than individuals with dissimilar traits. Three longitudinal studies using stochastic actor-based models found friendship network characteristics influenced change in individuals' body weight status and/or weight-related behaviour over time. Future research should focus on diverse populations and types of social networks and identifying the mechanisms by which social networks influence obesity to inform network-based interventions.

Body size reference norms and subjective weight status: A gender and life course approach

This paper uses data from The National Longitudinal Study of Adolescent to Adult Health (Add Health) to describe county-level variation in norms regarding physical weight among adolescents in the United States. We demonstrate that regardless of one's physical size, those residing in counties with a heavier weight norm are significantly less likely to see themselves as overweight than those residing in counties with a light weight norm. We further show that the local weight norm during adolescence (Wave 1) is associated with individuals' weight perceptions through adolescence and into young adulthood (Wave 4), though these associations attenuate in strength as respondents age. Our results suggest that weight norms have a stronger influence on weight perceptions among women compared to men and that the role of gender is particularly important during adolescence. We encourage life course researchers to consider the normative health environment during adolescence as an important context for understanding disparities in health and health lifestyles as people age.

Assessing Social Contagion in Body Mass Index, Overweight, and Obesity Using a Natural Experiment

IMPORTANCE

Little is known about whether the substantial clustering of obesity and overweight within social and geographic networks results from causal pathways, such as social contagion and shared environments, or from self-selection.

OBJECTIVES

This study aimed to determine whether exposure to communities with higher rates of obesity increases the body mass index (BMI) of individuals, calculated as weight in kilograms divided by height in meters squared, and their risk of being overweight or obese, and whether social contagion, shared environments, or self-selection can account for identified differences.

DESIGN, SETTING, AND PARTICIPANTS

This natural experiment study used the routine assignment of military service members to installations as a source of exogenous variation in exposure to communities with higher vs lower rates of obesity. The study, which used data collected by the Military Teenagers' Environments, Exercise, and Nutrition Study, examined families from 38 military installations around the United States to determine if individuals had higher BMI and greater odds of overweight and obesity when assigned to installations in counties with higher rates of obesity. The study also examined if the relationship persisted after controlling for shared built environments. The participants included 1 parent and 1 child aged 12 or 13 years from 1519 families of Army-enlisted personnel. Data analysis was completed from November 2016 to October 2017.

EXPOSURES

Adult obesity rate in the county where the assigned installation of the service member was located. Time at installation and location of residence (on-installation vs off-installation) were used to measure the degree of exposure.

MAIN OUTCOMES AND MEASURES

For parents, outcomes were BMI, overweight/obesity (BMI, ≥25) and obesity (BMI, ≥30). For children, outcomes were BMI z score, overweight/obesity (BMI percentile for age and sex, ≥85), and obesity (BMI percentile for age and sex, ≥95). These outcomes were based on self-reports for parents, self-reports and parent reports for all children, and anthropometric measurements for a subsample of children.

RESULTS

Members of 1519 families participated, including 1314 adults (of whom 740, or 56%, were fathers) and 1111 children (of whom 576, or 52%, were boys); anthropometric measurements were performed on 458 children. The sample was 40% white, 22% black, 24% Hispanic, and 14% other races/ethnicities. A 1-percentage point higher county obesity rate was associated with a higher BMI (a difference of 0.08; 95% CI, 0.02-0.13) and greater odds of obesity (adjusted odds ratio [aOR], 1.05; 95% CI, 1.02-1.08) in parents, and a higher BMI z score (0.01; 95% CI, 0.003-0.02) and greater odds of overweight/obesity (aOR, 1.04; 95% CI, 1.01-1.06) in children. The evidence supported stronger associations among families with more time at installation and off-installation residence. Associations persisted even after controlling for shared built environments.

CONCLUSIONS AND RELEVANCE

Exposure to counties with higher rates of obesity was associated with higher BMI and higher odds of overweight and/or obesity in parents and children. There was no evidence to support self-selection or shared built environments as possible explanations, which suggests the presence of social contagion in obesity.

Twitter as a means to study temporal behaviour

Biomedical research has exploited vital and other statistics (e.g., birth or death rates) for almost 200 years [1]. The Internet has become a rich source of digital databases, which are being used for many lines of research (e.g., circadian and seasonal [2] or metabolism [3,4]). Internet-based studies generally investigate large populations while individual social media accounts are rarely used to analyse, for example, individual sleep-wake behaviour (e.g., youtu.be/wBNcP-LkpfA). I therefore applied time series analyses, commonly used in circadian and sleep research, to approximately 12,000 tweets sent from a single Twitter account (@realdonaldtrump; December, 2014 to March, 2017). The account was clearly used by different individuals/groups launching tweets from various devices. Among these, the Android phone was the most consistent over the years. Its tweet activity peaked twice a day (early morning and late night), and both peaks showed a strong seasonality by tracking dawn.

Perceived Diet and Exercise Behaviors Among Social Network Members With Personal Lifestyle Habits of Public Housing Residents

Our objective was to characterize the relationship between public housing residents' diet/exercise habits with similar behaviors among their social network. We conducted a cross-sectional survey of randomly selected households in Baltimore, Maryland, from August 2014 to August 2015. Adult heads of household completed questions on diet, exercise, and perceived habits among network members. Our dependent variables were high added sugar intake (≥39.9 teaspoons/day), high fruit/vegetable intake (≥6.1 servings/day), and being physically active (≥moderately activity). Our network exposures were proportion of members perceived to daily consume (1) sugar-sweetened beverages, (2) sweets, (3) fruits, and (4) vegetables, as well as to weekly exercise (1) vigorously or (2) moderately. We used multivariate logistic regression to examine associations between habits with relevant network exposures. Our sample included 266 adults with mean age of 44.5 years, 86.1% women and 95.5% African American. We found a statistically significant association between study participants' high daily intake of added sugar with perceived network exposure to daily sugar-sweetened beverages (odds ratio [OR] = 1.10, 95% confidence interval [CI] [1.02, 1.20]) and daily sweets (OR = 1.10, 95% CI [1.02, 1.20]). Greater network exposure to weekly vigorous exercise was significantly associated with personally being physically active (OR = 1.15, 95% CI [1.04, 1.28]), but not network exposure to weekly moderate exercise. Among public housing residents, associations exist between individuals' and perceived networks' lifestyle habits of high added sugar foods consumption and vigorous exercise, which may hold promise for future social network interventions.

The social genome of friends and schoolmates in the National Longitudinal Study of Adolescent to Adult Health

Humans tend to form social relationships with others who resemble them. Whether this sorting of like with like arises from historical patterns of migration, meso-level social structures in modern society, or individual-level selection of similar peers remains unsettled. Recent research has evaluated the possibility that unobserved genotypes may play an important role in the creation of homophilous relationships. We extend this work by using data from 5,500 adolescents from the National Longitudinal Study of Adolescent to Adult Health (Add Health) to examine genetic similarities among pairs of friends. Although there is some evidence that friends have correlated genotypes, both at the whole-genome level as well as at trait-associated loci (via polygenic scores), further analysis suggests that meso-level forces, such as school assignment, are a principal source of genetic similarity between friends. We also observe apparent social-genetic effects in which polygenic scores of an individual's friends and schoolmates predict the individual's own educational attainment. In contrast, an individual's height is unassociated with the height genetics of peers.

Biological Networks Entropies: Examples in Neural Memory Networks, Genetic Regulation Networks and Social Epidemic Networks

Networks used in biological applications at different scales (molecule, cell and population) are of different types: neuronal, genetic, and social, but they share the same dynamical concepts, in their continuous differential versions (e.g., non-linear Wilson-Cowan system) as well as in their discrete Boolean versions (e.g., non-linear Hopfield system); in both cases, the notion of interaction graph G(J) associated to its Jacobian matrix J, and also the concepts of frustrated nodes, positive or negative circuits of G(J), kinetic energy, entropy, attractors, structural stability, etc., are relevant and useful for studying the dynamics and the robustness of these systems. We will give some general results available for both continuous and discrete biological networks, and then study some specific applications of three new notions of entropy: (i) attractor entropy, (ii) isochronal entropy and (iii) entropy centrality; in three domains: a neural network involved in the memory evocation, a genetic network responsible of the iron control and a social network accounting for the obesity spread in high school environment.

Network analysis of the NetHealth data: exploring co-evolution of individuals' social network positions and physical activities

Understanding the relationship between individuals' social networks and health could help devise public health interventions for reducing incidence of unhealthy behaviors or increasing prevalence of healthy ones. In this context, we explore the co-evolution of individuals' social network positions and physical activities. We are able to do so because the NetHealth study at the University of Notre Dame has generated both high-resolution longitudinal social network (e.g., SMS) data and high-resolution longitudinal health-related behavioral (e.g., Fitbit physical activity) data. We examine trait differences between (i) users whose social network positions (i.e., centralities) change over time versus those whose centralities remain stable, (ii) users whose Fitbit physical activities change over time versus those whose physical activities remain stable, and (iii) users whose centralities and their physical activities co-evolve, i.e., correlate with each other over time. We find that centralities of a majority of all nodes change with time. These users do not show any trait difference compared to time-stable users. However, if out of all users whose centralities change with time we focus on those whose physical activities also change with time, then the resulting users are more likely to be introverted than time-stable users. Moreover, users whose centralities and physical activities both change with time and whose evolving centralities are significantly correlated (i.e., co-evolve) with evolving physical activities are more likely to be introverted as well as anxious compared to those users who are time-stable and do not have a co-evolution relationship. Our network analysis framework reveals several links between individuals' social network structure, health-related behaviors, and the other (e.g., personality) traits. In the future, our study could lead to development of a predictive model of social network structure from behavioral/trait information and vice versa.

The statistical mechanics of human weight change

Over the past 35 years there has been a near doubling in the worldwide prevalence of obesity. Body Mass Index (BMI) distributions in high-income societies have increasingly shifted rightwards, corresponding to increases in average BMI that are due to well-studied changes in the socioeconomic environment. However, in addition to this shift, BMI distributions have also shown marked changes in their particular shape over time, exhibiting an ongoing right-skewed broadening that is not well understood. Here, we compile and analyze the largest data set so far of year-over-year BMI changes. The data confirm that, on average, heavy individuals become lighter while light individuals become heavier year-over-year, and also show that year-over-year BMI evolution is characterized by fluctuations with a magnitude that is linearly proportional to BMI. We find that the distribution of human BMIs is intrinsically dynamic-due to the short-term variability of human weight-and its shape is determined by a balance between deterministic drift towards a natural set point and diffusion resulting from random fluctuations in, e.g., diet and physical activity. We formulate a stochastic mathematical model for BMI dynamics, deriving a theoretical shape for the BMI distribution and offering a mechanism that may explain the right-skewed broadening of BMI distributions over time. An extension of the base model investigates the hypothesis that peer-to-peer social influence plays a role in BMI dynamics. While including this effect improves the fit with the data, indicating that correlations in the behavior of individuals with similar BMI may be important for BMI dynamics, testing social transmission against other plausible unmodeled effects and interpretations remains the subject of future work. Implications of our findings on the dynamics of BMI distributions for public health interventions are discussed.

Bariatric Surgery Patients and Their Families: Health, Physical Activity, and Social Support

BACKGROUND

This study evaluated the social environment of bariatric surgery patients in the preoperative period.

METHODS

Forty bariatric surgery patients (mean = 46.2 ± 11.2 years), 35 adult cohabitating family members (mean = 45.2 ± 12.7 years), and 15 cohabitating children (mean = 11.5 ± 3.6 years) were recruited from a large rural medical center. Adult participants (patients and family members) completed height, weight, body composition, blood draws, and physical activity assessments (accelerometry), as well as eating behavior and social support inventories before the patient underwent bariatric surgery. Child participants completed demographic, height, and weight assessment only.

RESULTS

Over 90 % of adult family members were overweight or obese (body mass index (BMI) ≥ 25 kg/m², as were 50 % of children (BMI percentile ≥ 85 %). More than one third (37.1 %) of family members met the criteria for moderate to severe insulin resistance. Physical activity measured by accelerometry was moderately correlated between the patient and adult family members (r = 0.46, p = 0.023). Bariatric surgery patients reported high levels of social support from their family members on multiple social support measures.

CONCLUSIONS

Many family members of bariatric surgery patients also lived with obesity and related comorbidities, and demonstrate high sedentary behavior. However, patients reported high levels of support from family members, including support in following a healthy diet and engaging in physical activity. Engaging families in behavior change may help bariatric surgery patients and their families to become healthier.

Racial disparities in health conditions among prisoners compared with the general population

This paper compares black-white health disparities among prisoners to disparities in the noninstitutionalized community to provide a more complete portrait of the nation’s heath. We use data from the 2004 Survey of Inmates in State and Federal Correctional Facilities and the 2002 and 2004 National Health and Nutrition Examination Survey for incarcerated and noninstitutionalized adult (aged 18–65) men and women, respectively. Health disparities between black and white male prisoners based on self-reported prevalence are similar to disparities in the general population for hypertension and diabetes but significantly reduced for kidney problems and stroke. Health disparities between black and white female prisoners are similar to disparities in the general population for obesity but significantly reduced for hypertension, diabetes, heart problems, kidney problems, and stroke. Our study reveals that prisoners report far worse health profiles than non-prisoners but there is differential health selection into prison for whites and blacks, and population health estimates for adult black men in particular underreport the true health burden for U.S. adults. Our findings highlight the importance of incorporating prison populations in demographic and public health analyses.

•

Inmates have poorer health overall than the noninstitutionalized population, but more so for white women demonstrating a differential health selection into prison.

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Health problems increase when inmates are included in national health statistics, especially for black men.

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U.S. health statistics may underestimate the health of the nation with potential consequences for understanding racial health disparities.

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Properly characterizing population health and health disparities requires the inclusion of incarcerated adults in mainstream epidemiologic studies.

Associations between friendship characteristics and HIV and HSV-2 status amongst young South African women in HPTN-068

INTRODUCTION

Prevalence of HIV among young women in South Africa remains extremely high. Adolescent peer groups have been found to be an important influence on a range of health behaviours. The characteristics of young women's friendships might influence their sexual health and HIV risk via connections to sexual partners, norms around sexual initiation and condom use, or provision of social support. We investigated associations between young women's friendships and their Herpes Simplex Virus Type 2 (HSV-2) and HIV infection status in rural South Africa.

METHODS

Our study is a cross-sectional, egocentric network analysis. In 2011 to 2012, we tested 13- to 20-year-old young women for HIV and HSV-2, and collected descriptions of five friendships for each. We generated summary measures describing friend socio-demographic characteristics and the number of friends perceived to have had sex. We used logistic regression to analyse associations between friend characteristics and participant HIV and HSV-2 infection, excluding likely perinatal HIV infections.

RESULTS

There were 2326 participants included in the study sample, among whom HIV and HSV-2 prevalence were 3.3% and 4.6% respectively. Adjusted for participant and friend socio-demographic characteristics, each additional friend at least one year older than the participant was associated with raised odds of HIV (odds ratio (OR) = 1.37, 95% CI 1.03 to 1.82) and HSV-2 (adjusted OR=1.41, 95% CI 1.18 to 1.69). Each additional friend perceived to have ever had sex also raised the odds of HIV (OR = 1.29, 95% CI 1.03 to 1.63) and HSV-2 (OR=1.18, 95% CI 1.03 to 1.35).

DISCUSSION

We found good evidence that a greater number of older friends and friends perceived to have had sex were associated with increased risk for HSV-2 and HIV infection among young women.

CONCLUSIONS

The characteristics of young women's friendships could contribute to their risk of HIV infection. The extent to which policies or programmes influence age-mixing and young women's normative environments should be considered.

Causal Spousal Health Spillover Effects and Implications for Program Evaluation

Current methods of cost effectiveness analysis implicitly assume zero spillovers among social ties. This can underestimate the benefits of health interventions and misallocate resources toward interventions with lower comprehensive effects. We discuss the implications of social spillovers for program evaluation and document the first evidence of causal spillovers of health behaviors between spouses by leveraging experimental data from the Lung Health Study (smoking) and COMBINE Study (drinking). We find large decreases in spousal substance use from treatments with a therapy component, which reduces the incremental cost effectiveness ratios of some treatments by 12 to 18 percent.

Estimating sibling spillovers in health: Evidence on symptoms

This paper estimates the sibling spillover effect in health symptoms using a sample of US adolescents from the National Longitudinal Study of Adolescent Health dataset. The research design of this paper is to restrict the sample to sibling pairs who are separated between schools, where one enters high school and the other middle school. Because of school separation, sibling pairs face independent health shocks from own school peers. The identification strategy further exploits variations in individual health across symptoms to control for unobserved individual heterogeneity, which flexibly partials out family correlated effects. Estimation results show that the sibling spillover effect is large as a one-standard-deviation increase in one sibling's frequency of developing a stomach ache or a loss of appetite increases the other sibling's frequency of having the same symptom by about 55% of a standard deviation. Further investigation suggests that the effect is not due to spillovers in drinking alcohol or depression, but probably due to the spread of contagious illnesses like the stomach flu.

Use of a mobile social networking intervention for weight management: a mixed-methods study protocol

INTRODUCTION

Obesity and physical inactivity are major societal challenges and significant contributors to the global burden of disease and healthcare costs. Information and communication technologies are increasingly being used in interventions to promote behaviour change in diet and physical activity. In particular, social networking platforms seem promising for the delivery of weight control interventions.We intend to pilot test an intervention involving the use of a social networking mobile application and tracking devices (Fitbit Flex 2 and Fitbit Aria scale) to promote the social comparison of weight and physical activity, in order to evaluate whether mechanisms of social influence lead to changes in those outcomes over the course of the study.

METHODS AND ANALYSIS

Mixed-methods study involving semi-structured interviews and a pre-post quasi-experimental pilot with one arm, where healthy participants in different body mass index (BMI) categories, aged between 19 and 35 years old, will be subjected to a social networking intervention over a 6-month period. The primary outcome is the average difference in weight before and after the intervention. Secondary outcomes include BMI, number of steps per day, engagement with the intervention, social support and system usability. Semi-structured interviews will assess participants' expectations and perceptions regarding the intervention.

ETHICS AND DISSEMINATION

Ethics approval was granted by Macquarie University's Human Research Ethics Committee for Medical Sciences on 3 November 2016 (ethics reference number 5201600716).The social network will be moderated by a researcher with clinical expertise, who will monitor and respond to concerns raised by participants. Monitoring will involve daily observation of measures collected by the fitness tracker and the wireless scale, as well as continuous supervision of forum interactions and posts. Additionally, a protocol is in place to monitor for participant misbehaviour and direct participants-in-need to appropriate sources of help.

Region-level obesity projections and an examination of its correlates in Quebec

OBJECTIVES

Regional public health policy-makers frequently adopt obesity programs and objectives that have been established at global, provincial/state or national levels. However, the presence of substantial inter-regional disparities could render this practice inefficient. Studies that collectively assess obesity prevalence, temporal trends and their heterogeneity at the region level are rare, though they could be used to support better regional surveillance and planning. To address this gap, our study projected obesity prevalence time series to 2023 for 16 health regions in Quebec. We also compared the extent to which yearly rates of increase (or slope) versus cross-sectional prevalence drove regional heterogeneity and correlated with obesity-related sociodemographic and behavioural characteristics.

METHODS

Projections were done using weighted compositional regression to fit and extrapolate obesity prevalence time series (1987-2012). Heterogeneity in obesity prevalence as a function of time and obesity slope were characterized using standard deviation. The correlation of region-level obesity prevalence and slope with 14 area-level obesity-related characteristics was assessed.

RESULTS

Obesity prevalence is projected to increase in all regions. Region-level heterogeneity in prevalence in 2012 (σ = 2.2%) is projected to increase to (σ = 3.1%) by 2023. The increase in prevalence heterogeneity appeared to be driven by region-level heterogeneity in slope (β = 0.22%-0.51%/year). Obesity-related characteristics were found to be more strongly correlated with slope than with prevalence.

CONCLUSION

Large area obesity trends mask substantial and increasing region-level disparities. Obesity slope appears to drive region-level heterogeneity and correlate strongly with explanatory factors, and may represent a pertinent metric for public health monitoring.

The role of smoking in social networks on smoking cessation and relapse among adults: A longitudinal study

Understanding the spread of smoking cessation and relapse within social networks may offer new approaches to further curb the smoking epidemic. Whether smoking behavior among social network members determines smoking cessation and relapse of adults however, is less known. For this study, longitudinal data of 4623 adults participating in the Dutch Longitudinal Internet Studies for the Social sciences (LISS) panel were collected in March 2013 with a follow-up in 2014. Logistic regression was used to examine the association between the proportion of smokers in social networks, and (1) smoking cessation (n=762) and (2) smoking relapse (n=1905). Analyses were adjusted for the size of the network, age, sex, and education. Respondents with the largest proportion of smokers in their social network were less likely to quit smoking (OR=0.25; 95% CI=0.11-0.66) and more likely to experience a relapse (6.08; 3.01-12.00). Smoking cessation and relapse were most strongly associated with the proportion of smokers among household members and friends. The proportion of smokers in family outside the household was not related to smoking cessation and smoking relapse. In conclusion, smoking behavior in social networks, especially among household members and friends, is strongly associated with smoking cessation and relapse. These findings further support the spread of smoking within social networks, and provide evidence for network-based interventions, particularly including household members and friends.

Leisure-Time Physical Activity and Characteristics of Social Network Support for Exercise Among Latinas

PURPOSE

To examine the association between characteristics of social support for exercise and moderate-to-vigorous leisure-time physical activity (LTPA) among Latinas.

DESIGN

This cross-sectional study used baseline data from a cluster randomized controlled trial.

SETTING

The study was conducted in 16 churches located in San Diego County.

PARTICIPANTS

Participants (N = 436) were Latinas between 18 and 65 years old who did not self-report >150 minutes or did not exceed 250 minutes of moderate-to-vigorous PA per week measured by accelerometer.

MEASURES

Latinas listed up to 6 individuals who had provided support for exercise within the past 6 months, including their gender, relationship with the respondent, types of support provided, and respondent's satisfaction with support. Self-reported LTPA was dichotomized (none vs any).

ANALYSES

We generated dyads between Latinas who named ≥1 supporter (n = 323) and each supporter they named (n = 569 dyads). Logistic regression analyses were conducted using generalized estimating equations to adjust for multiple observations per participant.

RESULTS

Having an exercise partner (odds ratio [OR]: 2.16; 95% confidence interval [CI]: 1.01-4.62), help with household duties (OR: 2.70; 95% CI: 1.35-3.38), being "very much" satisfied with support (OR: 2.33; 95% CI: 1.26-4.30), and naming >2 supporters (OR: 2.57; 95% CI: 1.06-6.25) was positively associated with LTPA.

CONCLUSIONS

Findings suggest specific aspects of support for exercise that should be targeted in future interventions to promote LTPA.

Do neighborhoods matter differently for movers and non-movers? Analysis of weight gain in the longitudinal dallas heart study

The few available population-based longitudinal studies examining the link between change in neighborhood condition and weight change to date have only examined neighborhood changes generated by residential mobility. Applying a difference-in-difference analytic framework to data from the Dallas Heart Study (DHS), a multi-ethnic, population-based cohort in Dallas County, TX, we evaluated the relationship between changes in neighborhood condition and weight change for both movers and non-movers over an approximate seven-year follow-up period. We employed a novel measure of neighborhood condition based on property appraisal data to capture temporally consistent measures of change in neighborhood condition regardless of residential mobility. We observed an inverse relationship between weight change and change in neighborhood condition which was more pronounced for non-movers (1.9 fewer kilograms gained per 1-standard deviation improvement in neighborhood condition) than for movers (1.5 fewer kilograms gained per 1-standard deviation improvement in neighborhood condition).

Gender-specific Pathways of Peer Influence on Adolescent Suicidal Behaviors

The author explores new directions of understanding the pathways of peer influence on adolescent suicidal behavior by leveraging quasi-experimental variation in exposure to peer suicidal behaviors and tracing the flows of influence throughout school environments and networks. The author uses variation in peers' family members' suicide attempts to deploy an across-grade level, within-school analysis to estimate causal effects. Key findings include a gender-specific pathway, whereby girls are affected by their female grademates' experiences with family member suicidality but are unaffected by their male grademates. These specific pathways allow novel approaches to be used that leverage the gender specificity of the influences within an instrumental variable analysis. The findings suggest large (gender-specific) peer effects on suicidal behaviors in adolescence.

Values, Norms, and Peer Effects on Weight Status

This study uses data from the European Social Survey in order to test the Prinstein-Dodge hypothesis that posits that peer effects may be larger in collectivistic than in individualistic societies. When defining individualism and collectivism at the country level, our results show that peer effects on obesity are indeed larger in collectivistic than in individualistic societies. However, when defining individualism and collectivism with individual values based on the Shalom Schwartz universal values theory, we find little support for this hypothesis.

Can longitudinal generalized estimating equation models distinguish network influence and homophily? An agent-based modeling approach to measurement characteristics

BACKGROUND

Connected individuals (or nodes) in a network are more likely to be similar than two randomly selected nodes due to homophily and/or network influence. Distinguishing between these two influences is an important goal in network analysis, and generalized estimating equation (GEE) analyses of longitudinal dyadic network data are an attractive approach. It is not known to what extent such regressions can accurately extract underlying data generating processes. Therefore our primary objective is to determine to what extent, and under what conditions, does the GEE-approach recreate the actual dynamics in an agent-based model.

METHODS

We generated simulated cohorts with pre-specified network characteristics and attachments in both static and dynamic networks, and we varied the presence of homophily and network influence. We then used statistical regression and examined the GEE model performance in each cohort to determine whether the model was able to detect the presence of homophily and network influence.

RESULTS

In cohorts with both static and dynamic networks, we find that the GEE models have excellent sensitivity and reasonable specificity for determining the presence or absence of network influence, but little ability to distinguish whether or not homophily is present.

CONCLUSIONS

The GEE models are a valuable tool to examine for the presence of network influence in longitudinal data, but are quite limited with respect to homophily.

Women's social eating environment and its associations with dietary behavior and weight management

As an unhealthy social eating environment is considered a risk factor for obesity, this study aimed to examine women's regular eating networks and the extent to which diet-related variables were associated with those of their regular eating companions. In Study Part I (N = 579), an egocentric network approach was used to investigate women's perceptions of their eating networks. In Study Part II (N = 262), the participants' most important eating companions responded to a similar survey, and the corresponding answers were matched. The results showed that women shared their meals most frequently with spouses and other family members. Women who dined more often with healthy eaters reported on average a higher diet quality and a lower body mass index (BMI), which were also significant after controlling for individual factors. Study Part II expanded these results by showing that different diet-related factors such as diet quality, eating styles and BMI were correlated between women and their most important eating companions (r = 0.16-0.30, p < 0.05). Moreover, an actor-partner interdependence model revealed that a higher diet quality of the eating companions was associated with a lower BMI in women, controlled for their own eating behavior (b = -0.45, p < 0.05). This study showed similarities and interdependence between women's dietary behavior and body weight and those of their regular eating companions. This might indicate that regular eating networks have a shared understanding of what constitutes a normal diet, which might be an important factor to consider in the promotion of healthy eating.

Alcohol consumption by youth: Peers, parents, or prices?

Using data from the National Longitudinal Survey of Adolescent to Adult Health, we estimate the effect of peers' alcohol consumption and alcohol prices on the drinking habits of high-school-age youth. We use the two-stage residual inclusion method to account for the endogeneity of peer drinking in nonlinear models. For our sample of high school students, we find that peer effects are statistically and economically significant regarding the choice to participate in drinking but are not significant for the frequency of drinking, including binge drinking. Regarding alcohol prices, even though we have good price variation in our sample, alcohol prices are not found to be significant. The results are important for policymakers who are considering policies to reduce underage drinking, as we conclude that no significant impact on underage drinking will result from low-tax states' increasing excise taxes on alcohol so they are similar to those of high-tax states. Policymakers may choose to focus instead on the influence of peers and changing the social norm behavior.

Friends and social contexts as unshared environments: a discordant sibling analysis of obesity- and health-related behaviors in young adolescents

OBJECTIVE

This study examines the contribution of best friends' weight and the peer social context (time spent alone versus with friends) as sources of unshared environment associated with variability in weight and health behaviors among weight-discordant siblings.

METHODS

Pairs of same-sex biologic siblings (N=40 pairs; ages 13-17) were originally recruited as part of a study evaluating putative factors contributing to differences in adiposity among weight-discordant siblings. Siblings were asked to bring their best friends to the laboratory and siblings and friends' height and weight were objectively measured. Siblings also completed multi-pass dietary recalls to assess energy intake and sugar sweetened beverage (SSB) consumption. Siblings' physical activity was measured using accelerometry. Experience sampling methodology was used to assess sedentary behaviors/screen time and the number of occasions siblings spent alone and in the presence of friends. Multilevel models were used to estimate the relationships between predictors (best friends' zBMI, time spent alone or with friends) and outcomes (siblings' zBMI and obesity-related health behaviors).

RESULTS

Best friends' zBMI was the best predictor of participants' zBMI, even when controlling for child's birth weight. Best friends' weight (zBMI) further predicted participants' SSB intake and time engaged in sedentary behaviors. Being active with friends was positively associated with participants' overall physical activity, whereas spending time alone was negatively associated with accelerometer counts regardless of siblings' adiposity.

CONCLUSIONS

A friends' weight and the social context are unshared environmental factors associated with variability in adiposity among biologically-related weight-discordant siblings.

Longitudinal social networks impacts on weight and weight-related behaviors assessed using mobile-based ecological momentary assessments: Study Protocols for the SPARC study

Background

The transition from the home to college is a phase in which emerging adults shift toward more unhealthy eating and physical activity patterns, higher body mass indices, thus increasing risk of overweight/obesity. Currently, little is understood about how changing friendship networks shape weight gain behaviors. This paper describes the recruitment, data collection, and data analytic protocols for the SPARC (Social impact of Physical Activity and nutRition in College) study, a longitudinal examination of the mechanisms by which friends and friendship networks influence nutrition and physical activity behaviors and weight gain in the transition to college life.

Methods

The SPARC study aims to follow 1450 university freshmen from a large university over an academic year, collecting data on multiple aspects of friends and friendship networks. Integrating multiple types of data related to student lives, ecological momentary assessments (EMAs) are administered via a cell phone application, devilSPARC. EMAs collected in four 1-week periods (a total of 4 EMA waves) are integrated with linked data from web-based surveys and anthropometric measurements conducted at four times points (for a total of eight data collection periods including EMAs, separated by ~1 month). University databases will provide student card data, allowing integration of both time-dated data on food purchasing, use of physical activity venues, and geographical information system (GIS) locations of these activities relative to other students in their social networks.

Discussion

Findings are intended to guide the development of more effective interventions to enhance behaviors among college students that protect against weight gain during college.

Peer Group Similarity in Perceptions of Pubertal Timing

Self-report measures of perceived pubertal timing correspond only weakly with clinical measures of "objective" physical development. Peer and school contexts shape adolescents' self-perceptions of pubertal timing. The current study examined associations between perceived pubertal timing and the pubertal timing reported by nominated friends and schoolmates. Participants included 2817 adolescents (Mage = 16.6; 49 % female; 16 % Black; 20 % Hispanic) from the National Longitudinal Study of Adolescent Health. Three measures of pubertal timing were included: age-standardized ratings of body changes, comparisons of development relative to peers (relative timing), and, in females, age at menarche. It was hypothesized that relative timing, which explicitly asks adolescents to compare themselves to their peers, would be related to the age-standardized pubertal timing of nominated friends and schoolmates. Surprisingly, there were no associations between relative timing and age-standardized pubertal timing reported by peers, suggesting that pubertal self-perceptions do not fluctuate in response to the average level of development in a friend group. Instead, males were similar to nominated friends and schoolmates in age-standardized ratings of body changes, and females were similar to nominated friends in relative timing, controlling for race, ethnicity, and age. Different self-report measures of pubertal timing index different underlying constructs, and the social processes that influence adolescents' perceptions of pubertal maturation may differ between genders.

The Local Food Environment and Body Mass Index among the Urban Poor in Accra, Ghana

Obesity in the sub-Saharan Africa region has been portrayed as a problem of affluence, partly because obesity has been found to be more common in urban areas and among the rich. Recent findings, however, reveal rising prevalence among the poor particularly the urban poor. A growing body of literature mostly in Western countries shows that obesity among the poor is partly the result of an obesogenic-built environment. Such studies are lacking in the African context. This study examines the characteristics of the local food environment in an urban poor setting in Accra, Ghana and further investigates the associated risk of obesity for residents. Data on the local food environment was collected using geographic positioning system (GPS) technology. The body mass indices (BMI) of females (15-49 years) and males (15-59 years) were calculated from measured weight and height. Data on the socio-demographic characteristics and lifestyle behaviors of respondents was also collected through a household survey. Spatial analysis tools were used to examine the characteristics of the local food environment while the influence of the food environment on BMI was examined using a two-level multilevel model. The measures of the food environment constituted the level 2 factors while individual socio-demographic characteristics and lifestyle behaviors constituted the level 1 factors. The local food environment in the study communities is suggestive of an obesogenic food environment characterized by an abundance of out-of-home cooked foods, convenience stores, and limited fruits and vegetables options. The results of the multilevel analysis reveal a 0.2 kg/m(2) increase in BMI for every additional convenience store and a 0.1 kg/m(2) reduction in BMI for every out-of-home cooked food place available in the study area after controlling for individual socio-demographic characteristics, lifestyle behaviors, and community characteristics. The findings of this study indicate that the local food environment in urban poor Accra is associated with increased risk of obesity through providing access to convenience stores. In order to reduce the risk of obesity in these urban poor communities, there is the need to regulate the availability of and access to convenience stores while also encouraging healthier offerings in convenience stores.

The Impact of Long-Term Physical Activity Interventions for Overweight/Obese Postmenopausal Women on Adiposity Indicators, Physical Capacity, and Mental Health Outcomes: A Systematic Review

Physical activity interventions have recently become a popular strategy to help postmenopausal women prevent and manage obesity. The current systematic review evaluates the efficacy of physical activity interventions among overweight and obese postmenopausal women and sheds light on the behavioral change techniques that were employed in order to direct future research. Method. Five electronic databases were searched to identify all prospective RCT studies that examine the impact of physical activity on adiposity indicators, physical capacity, and/or mental health outcomes among healthy, sedentary overweight, and obese postmenopausal women in North America. The behavior change technique taxonomy was used to identify the various strategies applied in the programs. Results. Five RCTs met the inclusion criteria. The findings showed that adiposity indicators and physical capacity outcomes significantly improved following long-term interventions; however, mental health outcomes showed nonsignificant changes. Furthermore, 17 behavior change techniques were identified with the taxonomy across all trials. The intrapersonal-level techniques were the most common. Conclusion. Physical activity interventions had a positive effect on adiposity measures and physical capacity. Future research should focus on testing the effectiveness of physical activity interventions on mental health and incorporate strategies at the individual and environmental level to maximize the health impact on the population.

School- and Individual-level Predictors of Weight Status Misperception among Korean Adolescents: A National Online Survey

Background

Growing body of literature has reported that weight status estimation pattern, including accurate-, under-, and overestimation, was associated with weight related behaviors and weight change among adolescents and young adults. However, there have been a few studies investigating the potential role of school contexts in shaping adolescents’ weight status estimation pattern among Korea adolescents.

Objective

The aim of the present study was to investigate the association between weight status misperception patterns and factors at individual-, family-, and school-level, simultaneously, and whether there was significant between schools variation in the distribution of each weight status misperception pattern, underestimation and overestimation respectively, among Korean adolescents aged 12–18 years.

Method

Data from the Eighth Korea Youth Risk Behavior Web-based Survey (KYRBS), 2012, a nationally representative online survey of 72,228 students (boys = 37,229, girls = 34,999) from a total of 797 middle and high schools were used. Sex stratified multilevel random intercept multinomial logistic models where adolescents (level 1) were nested within schools (level 2) were performed.

Results

At the school level, attending a school with higher average BMI (kg/m²) was positively associated with weight status underestimation, and inversely associated with weight status overestimation among boys and girls. Single-sex schooling was positively associated with weight status underestimation among girls. At the family level, higher household income (high/middle versus low) was inversely associated with both weight status under- and overestimation among boys and girls. Higher maternal education (equal to or more than college graduate versus equal to or less than high school graduate) was positively associated with weight status overestimation among boys, and living with both parents (compared to not living with both parents) was inversely associated with weight status underestimation among girls. At the individual level, high academic achievement (compared to low) was positively associated with weight status underestimation among boys and girls.

Conclusions

While further research with prospective designs and objectively measured anthropometric information is needed, school environmental factors such as sex composition and school average BMI, as well as, family contexts such as socioeconomic status need to be considered when developing and implementing obesity prevention programs.

Changes in Body Mass Index and Obesity Risk in Married Couples Over 25 Years: The ARIC Cohort Study

Married couples might be an appropriate target for obesity prevention interventions. In the present study, we aimed to evaluate whether an individual's risk of obesity is associated with spousal risk of obesity and whether an individual's change in body mass index (BMI; weight in kilograms divided by height in meters squared) is associated with spousal BMI change. We analyzed data from 3,889 spouse pairs in the Atherosclerosis Risk in Communities Study cohort who were sampled at ages 45-65 years from 1986 to 1989 and followed for up to 25 years. We estimated hazard ratios for incident obesity by whether spouses remained nonobese, became obese, remained obese, or became nonobese. We estimated the association of participants' BMI changes with concurrent spousal BMI changes using linear mixed models. Analyses were stratified by sex. At baseline, 22.6% of men and 24.7% of women were obese. Nonobese participants whose spouses became obese were more likely to become obese themselves (for men, hazard ratio = 1.78, 95% confidence interval: 1.30, 2.43; for women, hazard ratio = 1.89, 95% confidence interval: 1.39, 2.57). With each 1-unit increase in spousal BMI change, women's BMI change increased by 0.15 (95% confidence interval: 0.13, 0.18) and men's BMI change increased by 0.10 (95% confidence interval: 0.09, 0.12). Having a spouse become obese nearly doubles one's risk of becoming obese. Future research should consider exploring the efficacy of obesity prevention interventions in couples.

Self-reported health and gender: The role of social norms

The role of social norms in accounting for the different attitudes of men and women with respect to health is still an open issue. In this research, we investigate the role of social norms associated with specific gender environments in the workplace in accounting for differences in health-reporting behaviours across men and women. Using the 2010 European Working Conditions Survey, we build a database containing 30,124 observations. We first replicate the standard result that women report worse health than men, whatever the health outcome we consider. We then proxy social norms by the gender structure of the workplace environment and study how the latter affects self-reported health for men and women separately. Our findings indicate that individuals in workplaces where women are a majority tend to report worse health than individuals employed in male-dominated work environments, be they men or women. These results are robust to controlling for a large array of working condition indicators, which allows us to rule out that the poorer health status reported by individuals working in female-dominated environments could be due to worse job quality. This evidence suggests that social norms associated with specific gender environments play an important role in explaining differences in health-reporting behaviours across gender, at least in the workplace.

A call for research exploring social media influences on mothers' child feeding practices and childhood obesity risk

There is increasing interest in leveraging social media to prevent childhood obesity, however, the evidence base for how social media currently influences related behaviors and how interventions could be developed for these platforms is lacking. This commentary calls for research on the extent to which mothers use social media to learn about child feeding practices and the mechanisms through which social media influences their child feeding practices. Such formative research could be applied to the development and dissemination of evidence-based childhood obesity prevention programs that utilize social media. Mothers are identified as a uniquely important target audience for social media-based interventions because of their proximal influence on children's eating behavior and their high engagement with social media platforms. Understanding mothers' current behaviors, interests, and needs as they relate to their social media use and child feeding practices is an integral first step in the development of interventions that aim to engage mothers for obesity prevention. This commentary highlights the importance of mothers for childhood obesity prevention; discusses theoretical and analytic frameworks that can inform research on social media and mothers' child feeding practices; provides evidence that social media is an emerging context for social influences on mothers' attitudes and behaviors in which food is a salient topic; and suggests directions for future research.

Male Obesity

Many cross-sectional analyses and longitudinal studies have examined the association between adiposity and pubertal development. In addition, the impact of an increased fat mass on reproduction and fertility in human obese men and in male animal models of obesity has been studied. A trend toward earlier pubertal development and maturation in both sexes has been shown, and the notion that obese boys might progress to puberty at a slower pace than their nonobese peers can no longer be substantiated. Impaired fertility markers and reduced reproductive functions have been observed in obesity. Obesity affects both pubertal development and fertility in men.

Friends Like Me: Associations in Overweight/Obese Status among Adolescent Friends by Race/Ethnicity, Sex, and Friendship Type

BACKGROUND

Little is known about how interpersonal friend relationships are associated with obesity in young people, particularly with regard to how race/ethnicity, type of friendship, and sex affect the association between friends' and adolescents' weight status. This study examined associations in weight status among adolescents and their friends, exploring magnitudes of associations across friendship type, sex, and race/ethnicity.

METHODS

As part of EAT-2010 (Eating and Activity in Teens), friend nominations and anthropometrics were obtained from adolescents (n = 2099: 54% female; 80% nonwhite; mean age: 14.2 ± 1.9 years). Generalized estimating equation logistic regression models were used to test associations between adolescents' overweight/obese status and friends' (i.e., friend group, female friends, male friends, female best friends, and male best friends) overweight/obese status. Interactions by adolescent race/ethnicity were examined.

RESULTS

The majority of significant associations were observed among white female adolescents' who had a 22-40% higher prevalence of overweight/obesity if their friends were overweight compared to white females whose friends were not overweight. In contrast, there were few significant differences for other adolescent female and male racial/ethnic groups for girls and boys. Results for friend groups and best friends were generally similar to one another.

CONCLUSIONS

The association between friend and adolescent overweight/obese status depended on adolescents' sex, race/ethnicity, and friendship type. Given the similarities among friends, obesity interventions targeting youth, especially white females, should consider involving friends.

Stigma and the etiology of depression among the obese: An agent-based exploration

BACKGROUND

Obesity and depression are comorbid more often than chance predicts. However, depression among the obese is more common in settings where obesity is less common. This suggests that body habitus norms and social stigmatization may play a role in the etiology of depression among the obese.

METHODS

We developed an agent-based social network model to explore mechanisms by which deviance from normative body habitus may contribute to social isolation in the obese. At each of 240 simulated months (20 years), each agent updated its body mass index based on environmental, peer influence, and stochastic factors. At each month, each agent was subject to social ostracization and consequent depression if its body mass index deviated from that of its peers and the network-wide mean. We compared risk of depression as a function of obesity and obesity norms through simulations of a high-obesity context simulating the US state of Mississippi and a low-obesity context simulating the US state of Colorado, then explored the relationship between global obesogenic forces and agent-specific resistance to the forces.

RESULTS

Over 1000 simulations in each context, 25 percent of obese agents in simulated Colorado were ever-depressed as compared to 21 percent in simulated Mississippi, although 10 percent overall were ever-depressed in both settings. High and low levels of resistance to obesogeneity prevented the most depression, whereas medium resistance levels were more depressogenic.

CONCLUSIONS

Social stigma and ostracization that occur as a consequence of deviance from body habitus norms may be a plausible mechanism by which weight stigma may influence depression in the obese. Public health interventions targeting individuals rather than obesogenic environments may modify body habitus norms with the unintended consequence of increasing stigma-based social isolation among those who remain obese.

Overweight and obesity in India: policy issues from an exploratory multi-level analysis

This article analyses a nationally representative household dataset-the National Family Health Survey (NFHS-3) conducted in 2005 to 2006-to examine factors influencing the prevalence of overweight/obesity in India. The dataset was disaggregated into four sub-population groups-urban and rural females and males-and multi-level logit regression models were used to estimate the impact of particular covariates on the likelihood of overweight/obesity. The multi-level modelling approach aimed to identify individual and macro-level contextual factors influencing this health outcome. In contrast to most studies on low-income developing countries, the findings reveal that education for females beyond a particular level of educational attainment exhibits a negative relationship with the likelihood of overweight/obesity. This relationship was not observed for males. Muslim females and all Sikh sub-populations have a higher likelihood of overweight/obesity suggesting the importance of socio-cultural influences. The results also show that the relationship between wealth and the probability of overweight/obesity is stronger for males than females highlighting the differential impact of increasing socio-economic status on gender. Multi-level analysis reveals that states exerted an independent influence on the likelihood of overweight/obesity beyond individual-level covariates, reflecting the importance of spatially related contextual factors on overweight/obesity. While this study does not disentangle macro-level 'obesogenic' environmental factors from socio-cultural network influences, the results highlight the need to refrain from adopting a 'one size fits all' policy approach in addressing the overweight/obesity epidemic facing India. Instead, policy implementation requires a more nuanced and targeted approach to incorporate the growing recognition of socio-cultural and spatial contextual factors impacting on healthy behaviours.

Testing and Modeling Dependencies Between a Network and Nodal Attributes

Network analysis is often focused on characterizing the dependencies between network relations and node-level attributes. Potential relationships are typically explored by modeling the network as a function of the nodal attributes or by modeling the attributes as a function of the network. These methods require specification of the exact nature of the association between the network and attributes, reduce the network data to a small number of summary statistics, and are unable provide predictions simultaneously for missing attribute and network information. Existing methods that model the attributes and network jointly also assume the data are fully observed. In this article we introduce a unified approach to analysis that addresses these shortcomings. We use a previously developed latent variable model to obtain a low dimensional representation of the network in terms of node-specific network factors. We introduce a novel testing procedure to determine if dependencies exist between the network factors and attributes as a surrogate for a test of dependence between the network and attributes. We also present a joint model for the network relations and attributes, for use if the hypothesis of independence is rejected, that can capture a variety of dependence patterns and be used to make inference and predictions for missing observations.