There were plenty of people whose normal weight belied the higher cardiovascular risk evident in their waist size, according to a pooled analysis of over a dozen cohort studies.
Among those with normal weight or overweight measured by body mass index (BMI), a large waist circumference (WC) and a high waist-to-hip ratio (WHR) were associated with a 15% to 50% excess risk for most heart disease outcomes over 20 years, reported Michael Blaha, MD, MPH, of the Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease in Baltimore, and colleagues.
Notably, people with obesity and a small waist circumference had largely similar clinical outcomes to their normal-weight counterparts; the risk of all-cause mortality even favored some individuals with obesity and smaller waists.
Significance of Waist Measurements
“In our study of participants without a reported history of CHD [coronary heart disease], we demonstrated that relying on BMI alone, without accounting for measures of central adiposity, can obscure meaningful heterogeneity in CVD [cardiovascular disease] risk,” Blaha and team wrote in the Journal of the American College of Cardiology (JACC).
“WC and WHR identifies misclassification of conventional BMI categories and reclassifies CVD risk across normal weight, overweight, and obesity, adding diagnostic and prognostic value,” they emphasized. “We encourage clinicians to consider central adiposity distribution across the entire BMI spectrum when evaluating cardiovascular risk in primary prevention settings.”
In 2023, the American Medical Association advised against using BMI as a standalone diagnostic tool, given that it often fails to reflect actual body fat percentage. A Lancet Commission subsequently recommended that a clinical diagnosis of obesity be verified against at least one additional anthropometric measure (e.g., WC, WHR, waist-to-height ratio) or direct fat mass measurements.
In an accompanying editorial, Kershaw Patel, MD, of Houston Methodist DeBakey Heart and Vascular Center, and Neela Thangada, MD, MSCI, of Northwestern University’s Feinberg School of Medicine in Chicago, noted that prior to this study, the relative contributions of WC to specific CVD endpoints had been “a key knowledge gap in the field.”
Blaha and colleagues sought to fill the gap with a study population of 259,388 individuals from 15 cohorts predominantly in the U.S. Outcomes of interest were first fatal or nonfatal myocardial infarction, fatal or nonfatal stroke, heart failure, atrial fibrillation, total CHD, total CVD, CHD mortality, CVD mortality, and all-cause mortality.
Findings on Waist Circumference
The study followed the standard cutoffs for high WC (>88 cm for women, >102 cm for men) and high WHR (>0.85 for women, >0.90 for men). Traditional BMI calculations determined normal weight (BMI 18.5 to <25), overweight (BMI 25 to <30), and obesity (BMI ≥30).
Among individuals with normal weight, 5% had a large WC and 18% had a high WHR. For those with overweight, 39% had a large WC and 40% had a high WHR. Conversely, among those with obesity, 9% had a small WC and 45% had a low WHR.
For those with obesity, the population attributable risk associated with a large WC or a high WHR ranged from 13% to 49%, with high WC most strongly tied to heart failure and atrial fibrillation.
“It is time to abandon a sole focus on body mass index,” said JACC Editor-in-Chief Harlan Krumholz, MD, of the Yale School of Medicine in New Haven, Connecticut, in a statement.
“This enormously important study, based on data from hundreds of thousands of participants in large-scale cohort studies, authoritatively shows that waist circumference and waist-to-hip ratio provide critical information about cardiovascular risk, even among people with a BMI considered normal,” he continued. “Where fat is distributed matters, and these simple measures should be part of routine cardiovascular risk assessment.”
Future Research Directions
Patel and Thangada nevertheless cautioned that several major unknowns remain.
“Additional studies are needed to evaluate whether reducing central adiposity, rather than total body weight, is a mechanistically relevant target to modify CVD risk,” they suggested, adding that several important questions remain: “Does incorporation of these measures of central adiposity into existing models meaningfully improve CVD risk assessment? Are longitudinal changes in measures of central adiposity prognostically important and how frequently should WC and WHR be measured?”
Sex differences would also be a topic of interest. Blaha’s team reported that unlike men, women with obesity but low WHR were still at higher risk for the studied clinical outcomes compared with those with normal weight and low WHR, albeit with smaller hazard ratios than women with obesity and high WHR.
The study lacked measures of physical activity, diet, or genetic risks, the authors acknowledged. They also relied on a single assessment of WC and WHR, precluding longitudinal analysis, and could not exclude residual confounding from the observational study.
Disclaimer
The information provided in this article is for educational purposes only and is not intended to replace professional medical advice. Always consult with a healthcare provider for personal health decisions.
Fuente: https://www.medpagetoday.com/primarycare/obesity/122562
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