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Validity of self-reported body mass index among middle-aged participants in the Norwegian Women and Cancer study.

Skeie G, Mode N, Henningsen M, Borch KB - Clin Epidemiol (2015)

Bottom Line: Demographic and anthropometric were compared using t-tests and chi-square tests of independence.The distribution of BMI categories did not differ between self-reported and measured values.While there was substantial agreement between self-reported and measured BMI values, there was small but statistically significant under-reporting of weight and thus self-reported BMI.

View Article: PubMed Central - PubMed

Affiliation: Department of Community Medicine, UiT The Arctic University of Norway, Tromsø, Norway.

ABSTRACT

Background: Body mass index (BMI) based on self-reported height and weight has been criticized as being biased because of an observed tendency for overweight and obese people to overestimate height and underestimate weight, resulting in higher misclassification for these groups. We examined the validity of BMI based on self-reported values in a sample of Norwegian women aged 44-64 years.

Methods: The study sample of 1,837 participants in the Norwegian Women and Cancer study self-reported height and weight, and then, within 1 year, either self-reported anthropometric again, or were measured by medical staff. Demographic and anthropometric were compared using t-tests and chi-square tests of independence. Misclassification of BMI categories was assessed by weighted Cohen's kappa and Bland-Altman plot.

Results: On average, the two measurements were taken 8 months apart, and self-reported weight increased by 0.6 kg (P<0.05), and BMI by 0.2 kg/m(2) (P<0.05). The distribution of BMI categories did not differ between self-reported and measured values. There was substantial agreement between self-reported values and those measured by medical staff (weighted kappa 0.73). Under-reporting resulting in misclassification of BMI category was most common among overweight women (36%), but the highest proportion of extreme under-reporting was found in obese women (18% outside the 95% limits of agreement). The cumulative distribution curves for the measured and self-reported values closely followed each other, but measurements by medical staff were shifted slightly toward higher BMI values.

Conclusion: While there was substantial agreement between self-reported and measured BMI values, there was small but statistically significant under-reporting of weight and thus self-reported BMI. The tendency to under-report was largest among overweight women, while the largest degree of under-reporting was found in the obese group. Self-reported weight and height provide a valid ranking of BMI for middle-aged Norwegian women.

No MeSH data available.


Related in: MedlinePlus

Difference in BMI between the two measurements versus the average of the two values.Note: Dashed lines indicate overall mean and 95% limits of agreement, vertical lines indicate limits for overweight and obese BMI values.Abbreviation: BMI, body mass index.
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f2-clep-7-313: Difference in BMI between the two measurements versus the average of the two values.Note: Dashed lines indicate overall mean and 95% limits of agreement, vertical lines indicate limits for overweight and obese BMI values.Abbreviation: BMI, body mass index.

Mentions: The overall mean difference between the average of self-reported BMI and that measured by medical staff was −0.29 kg/m2, indicating a small bias toward under-reporting of BMI in self-reported values. The 95% limits of agreement (Figure 2) for the differences between the two measurements demonstrate both high overall precision and higher variation between measurements for women in the obese BMI category compared with those in the normal range. Women with an average BMI in the obese range were more likely to have under-reported their BMI beyond the 95% limits of agreement (18%, 6/33) than those with an average BMI in the overweight range (5%, 4/82). Over the entire range of BMI values, the level of agreement between the two measurements was substantial, as demonstrated by very similar cumulative distribution curves (Figure S1). The under-reporting was slightly greater than that observed for repeated self-reports, which also showed greater variation in the obese BMI range, with 12% of women outside the 95% limits of agreement compared with only 6% outside the limits for the remaining women (Figure 2).


Validity of self-reported body mass index among middle-aged participants in the Norwegian Women and Cancer study.

Skeie G, Mode N, Henningsen M, Borch KB - Clin Epidemiol (2015)

Difference in BMI between the two measurements versus the average of the two values.Note: Dashed lines indicate overall mean and 95% limits of agreement, vertical lines indicate limits for overweight and obese BMI values.Abbreviation: BMI, body mass index.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493970&req=5

f2-clep-7-313: Difference in BMI between the two measurements versus the average of the two values.Note: Dashed lines indicate overall mean and 95% limits of agreement, vertical lines indicate limits for overweight and obese BMI values.Abbreviation: BMI, body mass index.
Mentions: The overall mean difference between the average of self-reported BMI and that measured by medical staff was −0.29 kg/m2, indicating a small bias toward under-reporting of BMI in self-reported values. The 95% limits of agreement (Figure 2) for the differences between the two measurements demonstrate both high overall precision and higher variation between measurements for women in the obese BMI category compared with those in the normal range. Women with an average BMI in the obese range were more likely to have under-reported their BMI beyond the 95% limits of agreement (18%, 6/33) than those with an average BMI in the overweight range (5%, 4/82). Over the entire range of BMI values, the level of agreement between the two measurements was substantial, as demonstrated by very similar cumulative distribution curves (Figure S1). The under-reporting was slightly greater than that observed for repeated self-reports, which also showed greater variation in the obese BMI range, with 12% of women outside the 95% limits of agreement compared with only 6% outside the limits for the remaining women (Figure 2).

Bottom Line: Demographic and anthropometric were compared using t-tests and chi-square tests of independence.The distribution of BMI categories did not differ between self-reported and measured values.While there was substantial agreement between self-reported and measured BMI values, there was small but statistically significant under-reporting of weight and thus self-reported BMI.

View Article: PubMed Central - PubMed

Affiliation: Department of Community Medicine, UiT The Arctic University of Norway, Tromsø, Norway.

ABSTRACT

Background: Body mass index (BMI) based on self-reported height and weight has been criticized as being biased because of an observed tendency for overweight and obese people to overestimate height and underestimate weight, resulting in higher misclassification for these groups. We examined the validity of BMI based on self-reported values in a sample of Norwegian women aged 44-64 years.

Methods: The study sample of 1,837 participants in the Norwegian Women and Cancer study self-reported height and weight, and then, within 1 year, either self-reported anthropometric again, or were measured by medical staff. Demographic and anthropometric were compared using t-tests and chi-square tests of independence. Misclassification of BMI categories was assessed by weighted Cohen's kappa and Bland-Altman plot.

Results: On average, the two measurements were taken 8 months apart, and self-reported weight increased by 0.6 kg (P<0.05), and BMI by 0.2 kg/m(2) (P<0.05). The distribution of BMI categories did not differ between self-reported and measured values. There was substantial agreement between self-reported values and those measured by medical staff (weighted kappa 0.73). Under-reporting resulting in misclassification of BMI category was most common among overweight women (36%), but the highest proportion of extreme under-reporting was found in obese women (18% outside the 95% limits of agreement). The cumulative distribution curves for the measured and self-reported values closely followed each other, but measurements by medical staff were shifted slightly toward higher BMI values.

Conclusion: While there was substantial agreement between self-reported and measured BMI values, there was small but statistically significant under-reporting of weight and thus self-reported BMI. The tendency to under-report was largest among overweight women, while the largest degree of under-reporting was found in the obese group. Self-reported weight and height provide a valid ranking of BMI for middle-aged Norwegian women.

No MeSH data available.


Related in: MedlinePlus