Home environmental influences on adolescents' energy balance related behaviours. The HEIA cohort study

Abstract

The global obesity epidemic represents an enormous potential threat to public health, because overweight and obesity are major risk factors of non-communicable diseases. The prevalence of overweight has furthermore increased among children and adolescents worldwide, and creates a growing health challenge for the next generation as children who are overweight are more likely to become overweight and obese as adults. Dietary, physical activity and sedentary behaviours are energy balance related behaviours (EBRB) that positively or negatively are related to weight status. It is agreed upon that the obesity epidemic is driven by large environmental changes over the past few decades, negatively influencing the EBRB. Social inequalities are furthermore consistently observed in children’s and adolescents’ weight status and health behaviours. Thus, there is a need for research to identify environmental factors influencing children’s and adolescents EBRB across age and within diverse social groups, in order to establish good opportunities of a healthy future. The main aims of this thesis were first to investigate the changes and tracking in children’s dietary behaviours during the transition into adolescence, and possible differences by parental education. Second to examine how the home environment influences young adolescents’ dietary and sedentary behaviours between the ages of 11 and 13 years, including social differences as measured by parental education. Longitudinal data from the Norwegian HEalth In Adolescents (HEIA) cohort study (2007–09) is included. Data was collected through questionnaires among a baseline sample of 975 adolescents at the age of 11 years (T0), and followed up at age 12 (T1) and 13 (T2) years. Furthermore, questionnaires were collected from both mothers (n=738) and fathers (n=630) at T0, and followed up at T2. Dietary intakes of fruits, vegetables, energy dense snacks, sugar sweetened soft drinks and sugar sweetened squash were examined prospectively, as well as screen time behaviours of television and video viewing (TV/DVD), and computer and electronic game use (PC/game). Parental education, parental modelling, parental regulation, availability and accessibility were explored as possible determinants in the home environment. Analyses of tracking was used to investigate changes and stability in dietary behaviours over time, and mediation analyses explored possible influences of the home environment on adolescents’ prospective soft drink intake and screen time. Tracking of the frequency of fruit, vegetable and snack intake, and in the amount of soft drinks and squash consumption was observed among boys and girls between the ages of 11 and 13 years. The intake of soft drinks did furthermore increase significantly during this time period. An inverse association was found between level of parental education and tracking in adolescents’ soft drink and squash consumption, as higher odds of a stable low than a stable high intake of soft drinks and squash was observed among those with a higher level of parental education. A higher level of parental education did furthermore predict a lower intake of soft drinks at the age of 13 years. A higher availability and accessibility of soft drinks at home subsequently predicted an increased intake among adolescents between the ages of 11 and 13 years. Moreover, the relationship of parental education predicting adolescents’ soft drink intake was explained trough the accessibility of soft drinks at home, identified as a mediating factor. In addition, a higher level of parental education predicted less time spent on PC/games among 13 year olds. A positive relationship was observed between parental modelling and adolescents’ TV/DVD time and an inverse relationship between parental regulation and adolescents’ TV/DVD time was subsequently found between the ages of 11 and 13 years. Finally, maternal and paternal modelling of TV/DVD viewing were found to mediate the relationship of parental education predicting adolescents’ TV/DVD time at the age of 13 years. The present study contributes to international research by enhancing the understanding of children’s and adolescents’ dietary and sedentary behaviours in a longitudinal perspective. The findings indicate tracking of dietary behaviours between the ages of 11 and 13 years, and thus emphasize the importance of starting before the age of 11 years to prevent the establishment of unfavourable dietary behaviours later in adolescence. Moreover, the parental role in adolescents’ dietary and screen time behaviours is highlighted through availability and accessibility in the home, parental modelling and regulation by implying that raising awareness of these determinants may result in a healthier lifestyle which further can influence weight status. Finally, the present analyses emphasize differences by parental education in adolescents’ dietary and screen time behaviours which could contribute to social inequalities in health. The accessibility of soft drinks at home and parental modelling of TV/DVD time was identified as important targets in future health education and health promotion programs aiming to reduce social differences in such health behaviours among adolescents.