First results from a new National Cohort - Investigating Associations between Health Behaviors, Socio-Cultural Context, Obesity and Health Outcomes in School Children

Background: The prevalence of obesity quadrupled over the last 25 years among children, and has more than doubled among adolescents. This rapid increase of obesity raises important questions in regards to its etiology and how to prevent a further increase. The study of etiological factors that are linked to obesity and metabolic risk factors in children and tracking these factors and their interactions over time is of vital importance. School environments provide an important venue to collect relevant information on health behaviors in children and their association to the environment and health outcomes. However, they are also important vehicles to form and implement improved health behaviors. In order to address these issues the PhysicalGenesis Study was initiated in 2014 recruiting students from Seventh-day Adventists (SDA) schools from across the US. 

Objectives: The primary purpose of the PhysicalGenesis study is to investigate associations and interactions between physical fitness and activity, health behaviors, obesity, health and academic performance and transgenerational effects in students enrolled in US schools, grades 5-11. In this report we will present first results of the data collection that took place during the Spring of 2015.

Methods: A longitudinal school based cohort study of schoolchildren attending SDA schools in the US. All students attending 5^th to 11^thgrade are eligible to enroll in the study. The PhysicalGenesis study population has unique characteristics that can provide interesting insights in the associations and interactions between health behaviors and health outcomes as 59% of the students are SDA that may have a higher prevalence of certain health behaviors. Previous studies have shown that SDA adults have low smoking rates (2%), low alcohol consumption rate (<8%) and a very high prevalence of vegetarians (45%). The study population can thus provide interesting contrasts and facilitate the analysis. Data collection for the 2014/2015 school year was carried out between March and June of 2015 and recruited students from approximately 10 percent of all eligible schools. All participating students and their parents completed an online questionnaire that assessed demographics, health behaviors and lifestyle factors including  smoking status, physical activity, sedentary behaviors, dietary patterns, general health status, environmental factors and other important information that relate to the study goals of the project. Physical fitness was assessed using the FITNESSGRAM™ protocol. Body height and weight were measured at the time of the fitness tests and also reported in the questionnaire. Chi square tests, analysis of variance and logistic regression were used for the analysis.

Results: A total of 869 students in 89 schools were assessed during the pilot phase of the project from March 1 to June 15, 2015. Many of the school were characterized by small student populations, 42% had 25 or less students, 27% had between 26 and 75 students, 19% had between 76 and 150 students and 12% had more than 150 students. Cole sex and age adjusted BMI values showed that 20% were overweight and 9% were obese. Students attending smaller school had significantly higher odds of being obese after adjusting for sex, age and maternal education, than students attending larger schools. The odds ratio (OR) of being obese was 0.25 (CI 0.10-0.59) for the largest schools (more than 150 students) and 0.41 (CI 0.18-0.90) for schools that had between 26 and 75 students when compared to schools that had less than 25 students. Age was positively associated with obesity with an OR of 1.40 (CI 1.18-1.65).

Conclusions: Preliminary data is showing an interesting mix of small to medium sized schools from which the eligible student population is being recruited. The results indicate that school size is highly associated with obesity rates and may be an indicator of sociocultural and regional variation that will need to be further explored. The PhysicalGenesis Study has the potential to provide new data that can help to differentiate multidimensional factors that may contribute to obesity and other adverse health outcomes.