Are metabolically healthy obese individuals really a benign cardiovascular group? An analysis of 162,590 participants with measures of arterial stiffness in UK BIOBANK

Abstract Background There is conflicting evidence as to whether so called metabolically healthy but overweight and obese individuals are at increased cardiovascular risk or mortality. Purpose We assessed whether metabolic health correlates with vascular health among these individuals using severity of arterial stiffness as a proxy for vascular health and cardiovascular risk. Methods Participants in UK Biobank with body-mass index (BMI) and arterial stiffness index (ASI) recorded at initial assessment between 2006-2010, and free from stroke and myocardial infarction and not underweight (BMI<18.5kg/m2) were included. Participants were stratified by BMI (normal, overweight, obese) and presence of metabolic abnormalities (hypertension, diabetes, dyslipidaemia). The primary outcome was the severity of ASI analysed using multivariate-adjusted linear regression. Results Of 162,590 participants, 55.0% were female, mean age was 57 years (SD 8), 42.5% were overweight and 24.4% obese. Within the normal BMI strata, 50.7% had ≥1 metabolic abnormality. Compared to individuals with normal BMI and no metabolic abnormalities (ref group), increased weight or metabolic abnormalities were similarly associated with higher ASI; adjusted β-coefficient [β] 0.35, 95%CI 0.30 to 0.40 for participants with normal BMI and ≥1 metabolic abnormality; β 0.32, 95%CI 0.26 to 0.37 for overweight participants without metabolic abnormalities. Obese individuals with no metabolic abnormalities had higher ASI (β 0.65; 95%CI 0.57 to 0.74) but was lower than overweight participants with metabolic abnormalities (β 0.80; 95%CI 0.75 to 0.84). Obese participants with metabolic abnormalities had the highest ASI (β 1.07; 95%CI 1.02 to 1.12) among all six metabolic combinations, p<0.001 for each vs ref group. Sensitivity analysis suggested higher ASI with increasing number of metabolic abnormalities within BMI categories. Conclusion Excess weight and metabolic abnormalities, are independently associated with adverse measures of vascular health to a similar degree, suggesting that the so called metabolically healthy obese are not a benign group. Primary prevention strategies should be considered in overweight, or obese individuals even if metabolic abnormalities are absent.