Chiolero, Arnaud

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Letters to the EditorRE: “COMPARISONS OF THE STRENGTH OF ASSOCIATIONS WITH FUTURE TYPE 2 DIABETES RISK AMONGANTHROPOMETRIC OBESITY INDICATORS, INCLUDING WAIST-TO-HEIGHT RATIO: A META-ANALYSIS”Kodama et al. (1) conducted a systematic review of prospec-tive studies to compare the strength of associations of waist-to-height ratio, body mass index, waist circumference, andwaist-to-hip ratio, respectively, with type 2 diabetes. For a 1–standard deviation increase in these indices, the relative risk ofdiabetes was 1.62 (95% conﬁdence interval (CI): 1.48, 1.78)for waist-to-height ratio, 1.55 (95% CI: 1.43, 1.69) for bodymass index, 1.63 (95% CI: 1.49, 1.79) for waist circumference,and 1.52 (95% CI: 1.40, 1.66) for waist-to-hip ratio, respec-tively. The authors concluded that the waist-to-height ratio (orwaist circumference) is a better predictor of future diabetesthan is body mass index or waist-to-hip ratio (1). To betterevaluate the meaning of these observations, one must considerthe reliability of the waist circumference measurement in com-parison with the reliability of the other anthropometric indices.It is well established that the reliability of weight andheight measurements is higher than the reliability of waistcircumference and hip circumference measurements (2).Intraobserver and interobserver technical error and reliabilityof these measurements were systematically reviewed by Uli-jaszek and Kerr (2) and are reported in Table 1. The intra-observer reliability of all these metrics is high (reliabilitycoefﬁcients on average of 0.97 or above). However, whilethe interobserver reliability of weight or height is high, it islower for waist circumference and hip circumference (reli-ability coefﬁcient on average of 0.94 and 0.89, respectively).Similar observations were made in children (3).A low reliability implies a relatively large random measure-ment error for waist or hip circumference measurement. Be-cause of the regression dilution bias associatedwith the randommeasurement error in an exposure (4), estimates of the relativerisk of the outcome diabetes are underestimated for the waist-to-height ratio, waist circumference, or waist-to-hip ratio. Intheory, this would confer additional arguments for the useof waist circumference to assess the risk of diabetes if anadjustment is made for the regression dilution bias (5). Never-theless, in practice, the poor reliability of waist circumference,the difﬁculty to adjust for the regression dilution bias (4), andthe availability and high reliability of weight and height mea-surements suggest that the waist-to-height ratio, waist circum-ference, or waist-to-hip ratio should not be preferred to bodymass index to assess the risk of diabetes.ACKNOWLEDGMENTSConﬂict of interest: none declared.REFERENCES1. Kodama S, Horikawa C, Fujihara K, et al. Comparisons of thestrength of associations with future type 2 diabetes risk amonganthropometric obesity indicators, including waist-to-heightratio: a meta-analysis. Am J Epidemiol. 2012;176(11):959–969.2. Ulijaszek SJ, Kerr DA. Anthropometric measurement error and theassessment of nutritional status. Br J Nutr. 1999;82(3):165–177.3. Stomfai S, Ahrens W, Bammann K, et al. Intra- and inter-observer reliability in anthropometric measurements in children.Int J Obes. 2011;35(suppl 1):S45–S51.4. Hutcheon JA, Chiolero A, Hanley JA. Random measurementerror and regression dilution bias. BMJ. 2010;340:1402–1406.5. Knuiman MW, Divitini ML, Buzas JS, et al. Adjustment forregression dilution in epidemiological regression analyses. AnnEpidemiol. 1998;8(1):56–63.Arnaud Chiolero (e-mail: arnaud.chiolero@chuv.ch)Institute of Social and Preventive Medicine, UniversityHospital Center and University of Lausanne,1010 Lausanne, SwitzerlandDOI: 10.1093/aje/kwt037; Advance Access publication: March 28, 2013Table 1. Intraobserver and Interobserver Technical Error of Measurement and Reliability for the Measurement ofWeight, Height, Waist Circumference, and Hip CircumferenceaIntraobserver InterobserverTechnical Errorof MeasurementCoefficientof ReliabilityTechnical Errorof MeasurementCoefficientof ReliabilityMean Range Mean Range Mean Range Mean RangeWeight, kg 0.2 0.1–0.3 0.98 0.95–1.00 1.3 0.1–4.1 0.98 0.94–1.00Height, cm 0.4 0.1–1.3 0.98 0.93–0.99 0.4 0.2–0.8 0.99 0.95–1.00Waist circumference, cm 1.3 1.0–1.6 0.97 0.97–0.98 2.3 0.6–4.2 0.94 0.86–0.99Hip circumference, cm 1.3 1.2–1.4 0.97 0.96–0.99 2.8 0.7–6.1 0.89 0.68–0.99a Mean values and range are reported from a systematic review by Ulijaszek and Kerr (2).862 Am J Epidemiol. 2013;177(8):862–866American Journal of Epidemiology© The Author 2013. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School ofPublic Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.Vol. 177, No. 8

Re: "Comparisons of the Strength of Associations with Future Type 2 Diabetes Risk Among Anthropometric Obesity Indicators, Including Waist-to-Height Ratio: A Meta-Analysis”

Re: "Comparisons of the Strength of Associations with Future Type 2 Diabetes Risk Among Anthropometric Obesity Indicators, Including Waist-to-Height Ratio: A Meta-Analysis”

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