Racial Variation in the Association between Positive Urgency and Body Mass Index among American Children

Background: Positive urgency reflects a specific facet of impulsivity and correlates with several health-related risk behaviors such as obesity, food addiction, and substance use. However, less is known about whether positive urgency is similarly or differently associated with high body mass index (BMI) across diverse racial groups. Aim: The aim of this study was to investigate racial differences in the associations between positive urgency and BMI in 9-10-year-old children in the US. Materials and Methods: This cross-sectional study used the Adolescent Brain Cognitive Development (ABCD) study. Participants were 11590 American children between ages 9 and 10 years old. The independent variable was positive urgency measured by the Urgency, Premeditation (lack of), Perseverance (lack of), Sensation Seeking, Positive Urgency, Impulsive Behavior Scale (UPPS-SS). The primary outcome was BMI. Race was the moderator. Demographic variables (age and sex) were covariates. Mixed-effects regression models were used for data analysis to adjust for the nested nature of the ABCD data. We also used weights (propensity score) to generate nationally representative results. Results: In the pooled sample, race showed a statistically significant interaction with positive urgency on children’s BMI, indicating a stronger effect of positive urgency on BMI for White children, compared to African American children. Conclusion: The association between positive urgency and BMI seems to be weaker in African American children than in White American children. The role of individual-level risk factors such as impulsive traits may be smaller for African American than White American children. Future research should study the role of obesogenic environments and other area level indicators in altering the effects of individual-level risk factors on BMI and obesity. www.scholink.org/ojs/index.php/rhs Research in Health Science Vol. 5, No. 3, 2020 130 Published by SCHOLINK INC.


Aims
We borrowed data from the Adolescent Brain Cognitive Development (ABCD) study, which has a large, diverse, national sample of 9-10-year-old children (Alcohol Research: Current Reviews Editorial, 2018;Casey et al., 2018;Karcher, O'Brien, Kandala, & Barch, 2019;Lisdahl et al., 2018;Luciana et al., 2018), in order to conduct a study with the following two aims. First, to see if there is any association between positive urgency and BMI in American children. Second, to compare the association between positive urgency and BMI by race. We expected high positive urgency to be linked to higher BMI (Hypothesis 1), but we expected this association to be weaker for African American than White children (Hypothesis 2).
Our expected stronger association between impulsive personality and BMI in White than African American children was based on previously published work on the weaker effect of positive urgency on BMI in African American than White children (Assari, 2020c).

Design and Setting
For this cross-sectional study, we conducted a secondary analysis of existing data. We borrowed data from the Adolescent Brain Cognitive Development (ABCD) study (Alcohol Research: Current Reviews Editorial, 2018;Casey et al., 2018;Karcher et al., 2019;Lisdahl et al., 2018;Luciana et al., 2018). The ABCD is a national study of children's brain development in the US (Alcohol Research: Current Reviews Editorial, 2018; Auchter et al., 2018). The ABCD study protocol was approved by the Institutional Review Board (IRB) at the University of California, San Diego (UCSD), as well as several other institutions. The ABCD participants signed consent or assent, depending on their age (Auchter et al., 2018).
The current analysis included 11590 9-10 years old children who had data on our study variables, including baseline BMI and positive urgency. Children were included regardless of their race or ethnicity. No additional eligibility was considered for this analysis. As we used a fully de-identified data set, our study was exempt from a full review by the Institutional Review Board (IRB). www.scholink.org/ojs/index.php/rhs Research in Health Science Vol. 5, No. 3, 2020 132 Published by SCHOLINK INC.

Measures and Measurements
Positive urgency was measured using UPPS-SS (Lynam, Smith, Whiteside, & Cyders, 2006). Positive urgency is a construct that reflects an aspect of impulsivity. In this study, positive urgency was treated as a continuous measure, with a higher score indicating higher positive urgency traits (higher impulsivity). The UPPS-SS is a valid and reliable measure (Verdejo-Garcí a et al., 2010). Figure 1 shows the distribution of the predictor and outcomes. Race identified by the parents was a categorical variable: African American, Asian, other/mixed race, and White (reference group). Racial variation in sense of urgency is well described (Holochwost et al., 2016). Age was a continuous measure in months.
Sex, 1 for males and 0 for females, was a dichotomous variable. Parents reported the age of the children.

Data Analysis
This analysis was performed in the Data Analysis and Exploration Portal (DEAP), National Data Archive (NDA), and the National Institutes of Health (NIH). We reported both weighted and unweighted mean (SD) and frequencies (%) for continuous and categorical variables in the pooled sample and by race to summarize our descriptive statistics. Weights (propensity scores) were applied to generate nationally representative results. We also used Chi-square and Analysis of Variance (ANOVA) for comparison of racial groups. This study applied mixed (random) effects models to address the data's nested nature for our main analysis. As participants were nested within families, who were themselves nested within 21 sites, we corrected for non-independence of our sample. Two mixed-effects models were performed. Appendix 1 shows the result of testing assumptions. In both models, positive urgency was the predictor, BMI was the outcome, race was the moderator, and covariates included sex, age, family, site, and propensity score. Model 1 (no interaction) was our model in the absence of any interaction terms. Model 2 (the interaction model) was our model that also included interaction terms between race and positive urgency. Appendix 2 shows the formula used for Model 1 and Model 2 in the DEAP system. Regression coefficient (b), standard error (SE), and p-values were reported for our parameters.   show an overall effect of positive urgency on BMI in the pooled sample. This table also summarizes our mixed-effects regression model which included interaction terms between race and positive urgency.

Mixed Effects Models
Model 2 (Interaction Model) showed a significant interaction between race and positive urgency on BMI in the pooled sample.

Overall Associations and Racial Variations
Figure 1 explored the association between positive urgency and BMI in the pooled sample. As this figure shows, we could not find an overall effect of positive urgency on BMI in the pooled sample. Figure 2 shows an interaction between race and positive urgency on BMI in the pooled sample. This figure showed a significant interaction between race and positive urgency on BMI in the pooled sample.

Discussion
Our findings showed a stronger link between higher positive urgency and BMI in White than African American adolescents. While higher scores on positive urgency were associated with higher BMI levels in White children, positive urgency was less relevant to the BMI levels of African American children.
As mentioned before, literature has established a link between positive urgency and BMI (VanderBroek-Stice et al., 2017). Our main contribution was to document racial variation in this link. We are only aware of one study that has explored racial variation in the effect of positive urgency on health outcomes. Using the Adolescent Brain Cognitive Development (ABCD) study data, race is found to interact with suicidal behaviors on children's positive urgency, indicating a weaker link between suicidality and positive urgency for African American and other/mixed race children compared to their White counterparts (Assari, 2020c). To our knowledge, this is the first study that documents racial variation in the positive urgency-BMI link in children.
This is, however, not the first study to find weaker effects of economic and psychological risk factors on BMI of African American compared to White individuals. In various studies, these factors have been shown to have a stronger effect on BMI for White individuals (Assari, 2014(Assari, , 2019aAssari, 2020b;Assari & Caldwell, 2015;Carter & Assari, 2016). For example, sustained obesity has been correlated with sustained depression in White but not African American people (Carter & Assari, 2016). A study concluded that emotion regulation may be of highest salience as a predictor of obesity for White females than any other race by sex group (Carter & Assari, 2016). In other studies, high SES had a stronger association with BMI for White than African American children (Assari, 2018;Assari, Caldwell, & Bazargan, 2019;Assari, Thomas, Caldwell, & Mincy, 2018) and adults. It has been suggested that any source of social marginalization may reduce the salience of individual level risk factors on BMI and obesity (Assari, 2019b). Thus, although many previous studies have shown differential correlates of BMI by race, this is one of the first papers to document racial differences in the association between positive urgency and BMI in 9-10-year-old children.

Future Directions
A wide range of structural and environmental factors increase risk of obesity in African American communities. Such structural factors may be why we observe a diminished effect of individual-level risk factors such as a higher score on the positive urgency trait. For example, Kwate (2008) showed that, due to racial and residential segregation, food options for African American and White children are fried chicken and apples, respectively. Review studies have shown that a higher density of fast food stores may increase obesity in sections of society, regardless of personal risk factors (Fleischhacker, Evenson, Rodriguez, & Ammerman, 2011). Thus, some BMI inequalities are due to structural inequalities in food options (Black, Moon, & Baird, 2014). The same inequalities exist for exercise (Lopez & Hynes, 2006;McNeill, Kreuter, & Subramanian, 2006) and walking (Connor, 2006).
A unique set of social and psychological risk factors may be particularly relevant to the risk of obesity in African American communities and can potentially explain the weaker effect potential urgency has on www.scholink.org/ojs/index.php/rhs Research in Health Science Vol. 5, No. 3, 2020 136 Published by SCHOLINK INC.
Similarly, environmental influences may be a larger cause of obesity in African American than White families. In this view, individual-level predictors lose some of their effects, while structural factors show stronger influences on African American individuals outcomes such as obesity (Assari, 2020a;Assari, 2020).

Study Limitations
Like other studies, our study had a few limitations. Since the design was cross-sectional, the results do not imply causations but associations. This study did not measure all factors that could impact BMI and positive urgency. These include SES as well as access to food, diet, exercise, and health. Although the sample was not entirely random, by applying the ABCD propensity score (weights), our results are generalizable to 9-10-year-old children in the US. We also did not measure parents' BMI or feeding habits. Our sample size was unequal across racial groups, with a larger n in White, and smaller n in other racial groups. None of these limitations, however, are fatal flaws.

Implications for Policy and Practice
Our results may have implications for psychological and public health interventions and programs that aim to prevent obesity among racially diverse samples of American children. The results also have clinical implications for working with African American children at risk of obesity. Emotion regulation, impulsivity, and positive urgency may have less salient effects for a high BMI in African American than White children (Cummins et al., 2020;Frisco, Quiros, & Van Hook, 2016). Investing and addressing such impulsive traits may have a larger return for preventing high BMI in White than African American children. That means our results advocate for tailoring existing BMI prevention strategies across racial groups of children.

Research Implications
The observed racial differences also have research implications. Researchers tend to treat race as a control variable in BMI research (Quinto et al., 2011). This practice assumes that BMI and obesity correlates are similar across racial groups (Norman, Nyberg, Elinder, & Berlin, 2015). One size, however, does not fit all (Field, Camargo, & Ogino, 2013). Although race has a direct effect on BMI, it also alters the correlates of BMI. Thus, race should not be reduced to a control variable. Instead, intersections of race, sex, SES, and risk and protective factors should be investigated.

Conclusions
Positive urgency contributes differently to children's high BMI across racial groups. As our results showed, positive urgency may be a less salient psychological determinant of BMI for African American children, compared to White children. The results are of importance given racial variation in childhood BMI. More research is needed to understand why psychological risk factors such as positive urgency