title: Optimal central obesity measurement site for assessing cardiometabolic and type 2 diabetes risk in middle-aged adults.
abstract: OBJECTIVE
  Despite recommendations that central obesity assessment should be employed as a marker of cardiometabolic health, no consensus exists regarding measurement protocol. This study examined a range of anthropometric variables and their relationships with cardiometabolic features and type 2 diabetes in order to ascertain whether measurement site influences discriminatory accuracy. In particular, we compared waist circumference (WC) measured at two sites: (1) immediately below the lowest rib (WC rib) and (2) between the lowest rib and iliac crest (WC midway), which has been recommended by the World Health Organisation and International Diabetes Federation.
  
  
  METHODS
  This was a cross-sectional study involving a random sample of 2,002 men and women aged 46-73 years. Metabolic profiles and WC, hip circumference, pelvic width and body mass index (BMI) were determined. Correlation, logistic regression and area under the receiver operating characteristic curve analyses were used to evaluate obesity measurement relationships with metabolic risk phenotypes and type 2 diabetes.
  
  
  RESULTS
  WC rib measures displayed the strongest associations with non-optimal lipid and lipoprotein levels, high blood pressure, insulin resistance, impaired fasting glucose, a clustering of metabolic risk features and type 2 diabetes, in both genders. Rib-derived indices improved discrimination of type 2 diabetes by 3-7% compared to BMI and 2-6% compared to WC midway (in men) and 5-7% compared to BMI and 4-6% compared to WC midway (in women). A prediction model including BMI and central obesity displayed a significantly higher area under the curve for WC rib (0.78, P=0.003), Rib/height ratio (0.80, P<0.001), Rib/pelvis ratio (0.79, P<0.001), but not for WC midway (0.75, P=0.127), when compared to one with BMI alone (0.74).
  
  
  CONCLUSIONS
  WC rib is easier to assess and our data suggest that it is a better method for determining obesity-related cardiometabolic risk than WC midway. The clinical utility of rib-derived indices, or alternative WC measurements, deserves further investigation.
authors.affiliation: HRB Centre for Health and Diet Research, Department of Epidemiology and Public Health, University College Cork, Cork, Ireland.
authors.forename: Seán R
authors.initials: SR
authors.lastname: Millar
authors.affiliation: HRB Centre for Health and Diet Research, Department of Epidemiology and Public Health, University College Cork, Cork, Ireland.
authors.forename: Ivan J
authors.initials: IJ
authors.lastname: Perry
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway.
authors.forename: Jan
authors.initials: J
authors.lastname: Van den Broeck
authors.affiliation: HRB Centre for Health and Diet Research, Department of Epidemiology and Public Health, University College Cork, Cork, Ireland.
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Phillips
mesh_terms: D000328:Adult; D000368:Aged; D000886:Anthropometry; D002318:Cardiovascular Diseases / Q000209:etiology*; D016001:Confidence Intervals; D003924:Diabetes Mellitus, Type 2 / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D056128:Obesity, Abdominal / Q000473:pathology*; D016017:Odds Ratio; D012372:ROC Curve; D012307:Risk Factors