Independent Relevance of Different Measures of Adiposity for Carotid Intima-Media Thickness in 40 000 Adults in UK Biobank.

Background Uncertainty persists about carotid intima-media thickness (CIMT) as a marker of subclinical atherosclerosis and the independent relevance of different measures of adiposity for CIMT. We assessed the independent relevance of general adiposity (body mass index), central adiposity (waist circumference), and body composition (fat mass index and fat-free mass index) with CIMT among adults in the United Kingdom. Methods and Results Multivariable linear regression of cross-sectional analyses of UK Biobank assessed the mean percentage difference in CIMT associated with equivalent differences in adiposity measures. To assess independent associations, body mass index and waist circumference were mutually adjusted, as were fat mass index and fat-free mass index. Among 39 367 participants (mean [SD] age 64 [8] years, 52% female, 97% White), median (interquartile range) CIMT was 0.65 (0.14) mm in women and 0.69 (0.18) mm in men. All adiposity measures were linearly and positively associated with CIMT after adjusting for confounders. Fat-free mass index was most strongly associated with CIMT after adjustment for fat mass index (% difference in CIMT: 1.23 [95% CI 0.93-1.53] women; 3.44 [3.01-3.86] men), while associations of fat mass index were attenuated after adjustment for fat-free mass index (0.28 [-0.02, 0.58] women; -0.59 [-0.99, -0.18] men). After mutual adjustment, body mass index remained positively associated with CIMT, but waist circumference was completely attenuated. Conclusions Fat-free mass index was the adiposity measure most strongly associated with CIMT, suggesting that CIMT may reflect vascular compensatory remodeling rather than atherosclerosis. Hence, screening for subclinical atherosclerosis should evaluate carotid plaques in addition to CIMT.