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Abel Romero-Corral, Virend K. Somers, Justo Sierra-Johnson, Yoel Korenfeld, Simona Boarin, Josef Korinek, Michael D. Jensen, Gianfranco Parati, Francisco Lopez-Jimenez, Normal weight obesity: a risk factor for cardiometabolic dysregulation and cardiovascular mortality, European Heart Journal, Volume 31, Issue 6, March 2010, Pages 737–746, https://doi.org/10.1093/eurheartj/ehp487
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Abstract
We hypothesized that subjects with a normal body mass index (BMI), but high body fat (BF) content [normal weight obesity (NWO)], have a higher prevalence of cardiometabolic dysregulation and are at higher risk for cardiovascular (CV) mortality.
We analysed 6171 subjects >20 years of age from the Third National Health and Nutrition Examination Survey (NHANES III) and the NHANES III mortality study, whose BMI was within the normal range (18.5–24.9 kg/m2), and who underwent a complete evaluation that included body composition assessment, blood measurements, and assessment of CV risk factors. Survival information was available for >99% of the subjects after a median follow-up of 8.8 years. We divided our sample using sex-specific tertiles of BF%. The highest tertile of BF (>23.1% in men and >33.3% in women) was labelled as NWO. When compared with the low BF group, the prevalence of metabolic syndrome in subjects with NWO was four-fold higher (16.6 vs. 4.8%, P < 0.0001). Subjects with NWO also had higher prevalence of dyslipidaemia, hypertension (men), and CV disease (women). After adjustment, women with NWO showed a significant 2.2-fold increased risk for CV mortality (HR = 2.2; 95% CI, 1.03–4.67) in comparison to the low BF group.
Normal weight obesity, defined as the combination of normal BMI and high BF content, is associated with a high prevalence of cardiometabolic dysregulation, metabolic syndrome, and CV risk factors. In women, NWO is independently associated with increased risk for CV mortality.
Comments
We read with great interest the article "Normal weight obesity: a risk factor for cardiometabolic dysregulation and cardiovascular mortality"by Abel Romero-Corral et al. The authors concluded that BF(body fat) was associated with an increased risk for Cardiovascular mortality as a continuous variable (adjusted HR 1.07, 95% CI 1.01-1.14) and as sex- adjusted tertiles (adjusted HR 2.2, 95% CI 1.03-4.67) in women. But there was no association between Cardiovascular mortality and BF in men. And also, the lack of association was observed between total mortality and BF in men and women.[1] Unfortunately, the authors did not raise a reasonable explanation for the conclusion. We note that the investigators performed the statistical analyses with adjusting for waist circumference and waist-to-hip ratio, but not for BMI. However, BMI may be a real confounding factor which had effect on the result of the research. Several epidemiologic studies had shown the association between BMI and the risk of death [2,3]. Although the subjects enrolled in this study had a normal BMI (18.5-24.9 kg/m2), the difference between BF tertiles was significant(P<0.0001) [1]and the impact of BMI on mortality may still exist. According to the study of Pischon T et al[3], when BMI ranged from 18.5kg/m2 to 25kg/m2, the all- cause mortality declined with the BMI index increased, ( HR 1.39 ,95% CI 1.24-1.57, BMI 18.5-21.0 versus BMI 23.5-25.0). Whitlock G et al [4]reported the consistent result. Thus, BMI could seriously affect the mortality as a confounding factor even though a normal range(18.5-24.9 kg/m2). Under such condition, the relationship of BF and mortality must be considered carefully and further investigations should be worked up.
Cong Lu, MD Jian Xun Zhao, MD Yu Cheng Chen, MD Department of Cardiology, West China Hospital, Sichuan University, Chengdu, China E-mail: [email protected]
References
1. Abel Romero-Corral, Virend K. Somers, Justo Sierra-Johnson. Normal weight obesity: a risk factor for cardiometabolic dysregulation and cardiovascular mortality. Eur Heart J 2010;31:737-746.
2. Flegal KM, Graubard BI, Williamson DF, Gail MH. Cause-specific excess deaths associated with underweight, overweight, and obesity. JAMA 2007;298:2028-2037.
3. Pischon T, Boeing H, Hoffmann K, Bergmann M. General and abdominal adiposity and risk of death in Europe. N Engl J Med 2008;359:2105-2120.
4. Whitlock G, Lewington S, Sherliker P, Clarke R, Emberson J, Halsey J, Qizilbash N, Collins R, Peto R. Body-mass index and cause-specific mortality in 900 000 adults:collaborative analyses of 57 prospective studies. Lancet 2009;373:1083-1096.
Conflict of Interest:
None declared