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Web-based self-reported height, weight, and body mass index among Swedish adolescents: a validation study.

Ekström S, Kull I, Nilsson S, Bergström A - J. Med. Internet Res. (2015)

Bottom Line: Females underestimated weight to a higher extent than males and overweight and obese participants underestimated weight to a higher extent than normal-weight participants, which resulted in higher underestimation of BMI.In the multivariable prediction model, only gender and BMI status significantly predicted discrepancy between reported and measured BMI.Web-collected BMI may be used as a valid, quick, and cost-effective alternative to measured BMI among Swedish adolescents.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden. Sandra.Ekstrom@ki.se.

ABSTRACT

Background: Web-collected height and weight are increasingly used in epidemiological studies; however, the validity has rarely been evaluated.

Objective: The aim of the study was to validate self-reported height, weight, and corresponding body mass index (BMI) among Swedish adolescents aged approximately 16 years. A secondary aim was to investigate possible prediction factors for validity of self-reported BMI.

Methods: The study included 1698 adolescents from the population-based cohort BAMSE. Height and weight were collected through a Web-based questionnaire and subsequently measured using standard procedures. Differences between reported and measured height, weight, and corresponding BMI were compared by t tests and agreement was evaluated by Pearson correlation and Bland-Altman plots. Multivariable linear regression analysis was used to investigate whether lifestyle and demographic factors predicted validity of self-reported BMI.

Results: On average, weight was underestimated by 1.1 kg and height was overestimated by 0.5 cm, leading to an underestimation of BMI by 0.5 kg/m2. Correlation coefficients were .98 for height, .97 for weight, and .94 for BMI, and highly significant. Females underestimated weight to a higher extent than males and overweight and obese participants underestimated weight to a higher extent than normal-weight participants, which resulted in higher underestimation of BMI. Underweight participants, on the contrary, overestimated weight and correspondingly BMI. Overall, a high proportion of participants were classified into the correct BMI category; however, among overweight and obese participants, only 60.2% (139/231) and 46% (20/44) were correctly classified, respectively. In the multivariable prediction model, only gender and BMI status significantly predicted discrepancy between reported and measured BMI.

Conclusions: Web-collected BMI may be used as a valid, quick, and cost-effective alternative to measured BMI among Swedish adolescents. The accuracy of self-reported BMI declines with increasing BMI and self-reported BMI should not be used to estimate the prevalence of overweight or obesity.

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Histogram of difference between self-reported and measured a) height, b) weight, and c) BMI.
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figure1: Histogram of difference between self-reported and measured a) height, b) weight, and c) BMI.

Mentions: Figure 1 shows histograms of differences between self-reported and measured height, weight, and corresponding BMI. Differences ranged from –9.4 to 19.6 cm for height, –24.9 to 16.3 kg for weight, and –7.5 to 5.4 kg/m2 for BMI. The differences were relatively normally distributed, although somewhat negatively skewed for weight and BMI. A higher proportion of females compared to males recalled their height within 1 and 2 cm, respectively (550/889, 61.9% and 788/889, 88.6% among females; 415/809, 51.3% and 620/809, 76.6% among males). No such differences were observed for comparable weight or BMI categories (data not shown).


Web-based self-reported height, weight, and body mass index among Swedish adolescents: a validation study.

Ekström S, Kull I, Nilsson S, Bergström A - J. Med. Internet Res. (2015)

Histogram of difference between self-reported and measured a) height, b) weight, and c) BMI.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4382564&req=5

figure1: Histogram of difference between self-reported and measured a) height, b) weight, and c) BMI.
Mentions: Figure 1 shows histograms of differences between self-reported and measured height, weight, and corresponding BMI. Differences ranged from –9.4 to 19.6 cm for height, –24.9 to 16.3 kg for weight, and –7.5 to 5.4 kg/m2 for BMI. The differences were relatively normally distributed, although somewhat negatively skewed for weight and BMI. A higher proportion of females compared to males recalled their height within 1 and 2 cm, respectively (550/889, 61.9% and 788/889, 88.6% among females; 415/809, 51.3% and 620/809, 76.6% among males). No such differences were observed for comparable weight or BMI categories (data not shown).

Bottom Line: Females underestimated weight to a higher extent than males and overweight and obese participants underestimated weight to a higher extent than normal-weight participants, which resulted in higher underestimation of BMI.In the multivariable prediction model, only gender and BMI status significantly predicted discrepancy between reported and measured BMI.Web-collected BMI may be used as a valid, quick, and cost-effective alternative to measured BMI among Swedish adolescents.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden. Sandra.Ekstrom@ki.se.

ABSTRACT

Background: Web-collected height and weight are increasingly used in epidemiological studies; however, the validity has rarely been evaluated.

Objective: The aim of the study was to validate self-reported height, weight, and corresponding body mass index (BMI) among Swedish adolescents aged approximately 16 years. A secondary aim was to investigate possible prediction factors for validity of self-reported BMI.

Methods: The study included 1698 adolescents from the population-based cohort BAMSE. Height and weight were collected through a Web-based questionnaire and subsequently measured using standard procedures. Differences between reported and measured height, weight, and corresponding BMI were compared by t tests and agreement was evaluated by Pearson correlation and Bland-Altman plots. Multivariable linear regression analysis was used to investigate whether lifestyle and demographic factors predicted validity of self-reported BMI.

Results: On average, weight was underestimated by 1.1 kg and height was overestimated by 0.5 cm, leading to an underestimation of BMI by 0.5 kg/m2. Correlation coefficients were .98 for height, .97 for weight, and .94 for BMI, and highly significant. Females underestimated weight to a higher extent than males and overweight and obese participants underestimated weight to a higher extent than normal-weight participants, which resulted in higher underestimation of BMI. Underweight participants, on the contrary, overestimated weight and correspondingly BMI. Overall, a high proportion of participants were classified into the correct BMI category; however, among overweight and obese participants, only 60.2% (139/231) and 46% (20/44) were correctly classified, respectively. In the multivariable prediction model, only gender and BMI status significantly predicted discrepancy between reported and measured BMI.

Conclusions: Web-collected BMI may be used as a valid, quick, and cost-effective alternative to measured BMI among Swedish adolescents. The accuracy of self-reported BMI declines with increasing BMI and self-reported BMI should not be used to estimate the prevalence of overweight or obesity.

Show MeSH
Related in: MedlinePlus