Influence of the home environment on diet quality and weight status of adolescents : a social ecological framework
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The home environment is a critical setting for the development of weight status in adolescence. At present a limited number of valid and reliable tools are available to evaluate the weight-related comprehensive home environment of this population. Aim 1a was to develop and validate the Multidimensional Home Environment Scale (MHES), which measures multiple components of the home. This scale includes psychological, social, and environmental domains from the perspective of adolescents and their mothers. After establishing content validity via an expert panel in nutrition, a validation sample of 218 mother-adolescent dyads completed a demographics survey and original version of the MHES. A focus group with the target population of adolescents (n=7) was conducted and feedback regarding item difficulty, content, bias, and relevance was incorporated. Principal components analysis yielded a 12-factor structure for adolescents and 14-factor structure for mothers. Internal consistency reliability was achieved for the majority of subscales, with α=0.5-0.9 for adolescents and α=0.7-0.9 for mothers. In addition, the MHES showed test-retest reliability for both adolescents (r=0.90) and mothers (r=0.91). Aim 1 b was to develop and validate a Nutrition Knowledge scale using the same sample as Aim 1a. Nutrition knowledge was assessed in this sample of 114 dyads. A 20-item scale was modified from previous version developed by the author. This instrument was composed of multiple-choice questions classified into four categories of knowledge: macronutrient, micronutrient, healthy eating and physical activity recommendations and fast-food nutrition. Content validity of the scale was established using feedback from an expert panel in nutrition (n=10) and a focus group of the sample population tested (n=7). The scale demonstrated high internal consistency reliability (adolescents: α=0.70, mothers: α=0.78) and test-retest reliability (adolescents: r=0.47, p=0.01, mothers: r=0.77, p=0.00). Aim 2 was to examine the impact of the comprehensive home environment on diet quality and weight status of adolescents using the MHES. A sample of 206 mothers and adolescents were recruited from local middle schools in the Austin area and completed a demographics survey, final version of the MHES, Food Frequency Questionnaire, and a Nutrition Knowledge scale online. Weight and height of adolescents were measured by the author using a standard protocols. Body Mass Index (BMI)-for-age percentiles were determined using the Center for Disease Control growth charts. Diet quality was estimated using the Healthy Eating Index-2010. Two models were created and reported in this dissertation. The first univariate model included each of the home environment factors as independent variables, and diet quality and BMI as dependent variables. The second model was developed using significant variables only from the initial model. Availability of healthy foods (p=0.00), healthy eating attitude (p=0.01), and accessibility to unhealthy foods (p=0.04) in the home were the strongest predictors of diet quality. Self-efficacy (p=0.02) and availability of healthy foods (p=0.02) emerged as significant predictors of BMI. Aim 3 of this dissertation research was to determine the effect of nutrition knowledge on the home environment and diet quality using the Healthy Eating Index-2010. This aim was accomplished using the same sample as Aim 2. It was hypothesized that the comprehensive home, with its psychological, social, and environmental features, would mediate the relationship between maternal nutrition knowledge and diet quality. A non-linear relationship between nutrition knowledge of the mother and diet quality of the adolescent was observed. Inclusion of the mediator in the model yielded significant estimates of the indirect effect (β=0.61, 95% CI: 0.3-1.0), with a 65.2% reduction in the model. This suggests that the home environment functioned as a partial mediator of the influence of nutrition knowledge on diet quality. Then, mediation analysis with the combination of psychological, social, and environmental factors was conducted in three separate regressions. Psychological (β=0.46), social (β=0.23), and environmental (β=0.65) variables were all significant mediators of nutrition knowledge on diet quality. Collectively, these results suggest that the MHES is an appropriate tool for measurement of the nutritional home environment of adolescents. The home environment appeared to significantly modulate diet quality and BMI of adolescents, particularly with respect to availability of healthy foods, healthy eating attitudes, and self-efficacy.