n e w e ng l a n d j o u r na l
m e dic i n e
component required for proof. Although the formal statistical boundary was conservative and evaluated only after accrual of ample data, the board elected to continue the trial for an additional 6 months after the boundary was crossed. Data that were accrued thereafter independently confirmed both the magnitude and statisticalsignificance of the apparent benefit. We thus respectfully disagree with Pierard and Davis. The board appropriately protected the interests of society and the trial participants and provided a valid estimate of the treatment effect.4 The evaluation by Koller et al. ignores the significant reduction in death from any cause that we observed. If death from any cause is added to our primary compositeoutcome (a standard ap-
proach to account for competing risks), then the absolute risk difference increases and the number needed to treat declines. Paul M Ridker, M.D. Robert J. Glynn, Sc.D.
Brigham and Women’s Hospital Boston, MA 02115 email@example.com
1. Ridker PM, Cannon CP, Morrow D, et al. C-reactive protein lev-
els and outcomes after statin therapy. N Engl J Med 2005;352:20-8. 2.Morrow DA, de Lemos JA, Sabatine MS, et al. Clinical relevance of C-reactive protein during follow-up of patients with acute coronary syndromes in the Aggrastat-to-Zocor Trial. Circulation 2006;114:281-8. 3. Pocock SJ. Current controversies in data monitoring for clinical trials. Clin Trials 2006;3:513-21. 4. Goodman SN. Stopping at nothing? Some dilemmas of data monitoring in clinical trials. AnnIntern Med 2007;146:882-7.
Obesity and Risk of Death
To the Editor: A challenging issue with the study reported on by Pischon et al. (Nov. 13 issue)1 is where to measure the waist. The accepted standard for measuring the waist circumference put forth by the third National Health and Nutrition Examination Surveys (NHANES III) protocol,2 as noted by Mahley in the Williams Textbook ofEndocrinology,3 is: “to measure waist circumference, locate the top of the right iliac crest. Place a measuring tape in a horizontal plane around the abdomen at the level of the iliac crest. Before reading the tape measure, ensure that the tape is snug but does not compress the skin and is parallel to the floor. Measurement is made at the end of a normal expiration.” However, Pischon et al. report that intheir study, “waist circumference was measured either at the narrowest circumference of the torso or at the midpoint between the lower ribs and the iliac crest.” International acceptance of measurement tools is paramount. Margaret M. Gaglione, M.D.
Tidewater Bariatrics Chesapeake, VA 23320 firstname.lastname@example.org
1. Pischon T, Boeing H, Hoffmann K, et al. General and ab-
dominal adiposity and risk ofdeath in Europe. N Engl J Med 2008;359:2105-20. 2. Department of Health and Human Services, Public Health Service. NHANES III anthropometric procedures video. Washington, DC: Government Printing Office, 1996. 3. Mahley RW. Disorders of lipid metabolism. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR, eds. Williams textbook of endocrinology. 11th ed. Philadelphia: Saunders Elsevier, 2008:1589-631.
To the Editor: Pischon et al. support the use of waist circumference or waist-to-hip ratio in addition to body-mass index (BMI) in assessing the risk of death. Engeland et al. found that height is inversely associated with mortality among men and to some degree among women.1 My recent study2 and a meta-analysis,3 both of which used cross-sectional data, provide support for the superiorityof measures of central obesity — especially waist-to-height ratio — over BMI for discriminating the presence or absence of cardiologic and metabolic risk factors. Pischon et al. appropriately adjusted for height when calculating the mortality risk associated with anthropometric indexes. It would be helpful if the authors would determine the relative risk of death according to waist-to-height...