Agreement Between self-reported weight and height with measured values in Otago adolescents, and associated factors.
Kerr, Rachael Jade
Background: New Zealand has the third highest rate of obesity in the world. Monitoring health trends from a young age can help health promotors get a better idea of what is happening as our population ages and can provide insight into challenges that different age group faces in terms of health. Adolescents are a key part of our population to monitor as they are old enough to start making their own decisions, but are still young enough to be positively influences about lifestyle habits. Self-reports have always been a controversial area of data collection due to the human error in reporting. Previous studies have assessed the agreement between self-reported and measured height, weight and calculated from these values, body mass index (BMI), in adolescents however, no studies have investigated ability of New Zealand adolescents to self-report. Objective: The aim of the current study is to investigate if Otago adolescents could accurately self-report weight and height, if these self-reported values could be used to calculate and accurately place individuals into the correct BMI categories, and if not, what factors influenced adolescent’s ability to self-report. Design: The Otago Secondary Schools Lifestyle Survey Two (OSSLS2) provided the cross-sectional data for this thesis. Participants completed an online survey which consisted of a set of seven questionnaires which collected data on several aspects of nutrition and health. Weights and heights were measured by trained researchers after completion of the relevant self-report questions. Bland Altman plots were used to assess the agreement of the data between self-reported and measured values. Results: 681 Otago secondary students participated from 11 schools across the area, and on average, adolescents significantly underestimated height and weight by 2cm and 0.8kg respectively (both p<0.001). BMI was significantly overestimated by 0.6kg/m2 (p<0.001). However, 81.7% were categorized into the correct BMI category using self-reported height and weight. Male adolescents underestimated height to a greater extent than their female peers (mean difference -2.5cm, p= 0.029). 25% of overweight and 39% of obese participants significantly underestimated their weight by a mean 2.3kg and 5.5kg more so than those in the normal BMI category (both p<0.05). Conclusion: Despite some misclassification, the Bland-Altman plots showed that self-reports for this population were accurate considering the extreme body changes adolescents go through during this time. Some groups within this population did tend to underestimate weight to a greater extent than others, however the 81.7% of the population could be correctly placed into the correct BMI category by the self-reported values the adolescents provided. This shows the usefulness that self-reported data can bring to large population based studies with limited time, budget or resources and could be useful in epidemiological studies.
Advisor: Skidmore, Paula; Haszard, Jill
Degree Name: Master of Dietetics
Degree Discipline: Human Nutrition
Publisher: University of Otago
Keywords: weight; height; bmi; measured; actual; adolescents
Research Type: Thesis