Waist-to-height ratio and body fat percentage as risk factors for ischemic cardiovascular disease: a prospective cohort study from UK Biobank

Abstract

Background: The independent effect of waist-to-height ratio (WHtR) and body fat percentage (BF%) on ischemic cardiovascular disease (CVD) remains uncertain.

Objectives: This study aimed to investigate the independent associations of WHtR and BF% with ischemic CVD.

Methods: This prospective cohort study used data from the UK Biobank. BF% was calculated as fat mass divided by body weight, measured by bioimpedance. Cox models estimated hazard ratios (HRs) with 95% confidence intervals (CIs) for overall and sex-specific associations of BF% and WHtR with risks of ischemic CVD and its main subtypes [myocardial infarction (MI) and ischemic stroke (IS)], adjusted for a range of potential confounders, including mutual adjustment for BF% and WHtR.

Results: In total, 468,333 participants without existing CVD were included in the analysis. During 12 y of follow-up, 20,151 ischemic CVD events, 13,604 MIs, and 6681 ISs were recorded. WHtR was linearly associated with ischemic CVD, MI, and IS, with an HR per 5% increase of 1.23 (95% CI: 1.20, 1.25), 1.24 (95% CI: 1.21, 1.27), and 1.22 (95% CI: 1.18, 1.26), respectively, independent of BF%. A stronger association between WHtR and MI was seen in females than in males. The association of BF% with these outcomes was substantially attenuated in both sexes after adjustment for WHtR. For example, in females, the HR (highest compared with lowest fifth) was reduced from 1.94 (95% CI: 1.76, 2.15) to 1.04 (95% CI: 0.90, 1.01) for ischemic CVD, from 2.04 (95% CI: 1.79, 2.32) to 0.97 (95% CI: 0.81, 1.16) for MI, and from 1.81 (95% CI: 1.54, 2.13) to 1.07 (95% CI: 0.85, 1.33) for IS.

Conclusions: WHtR, when used as a proxy measure for central obesity, is linearly associated with ischemic CVD in both sexes, which is independent of BF%. In contrast, the relationship of BF% with these health outcomes is predominantly driven by its correlation with WHtR.

Keywords: UK Biobank; body fat percentage; ischemic cardiovascular diseases; ischemic stroke; myocardial infarction; waist-to-height ratio.

FIGURE 1

Associations between waist-to-height ratio, body fat percentage, and ischemic cardiovascular diseases (using sex-specific quintiles). Red solid lines show the associations estimated in model 1, i.e., without mutual adjustment of body fat percentage and waist-to-height ratio. Blue dotted lines show the associations estimated in model 2, i.e., with mutual adjustment of body fat percentage and waist-to-height ratio. Models were stratified by region, age group, education, and ethnicity and adjusted for sex, deprivation, smoking status, drinking status, and physical activity. Fifths were defined using sex-specific quintiles. Analysis of the overall cohort was additionally adjusted for sex. HR, hazard ratio.

FIGURE 2

Subgroup analysis for sex-specific associations between waist-to-height ratio and ischemic cardiovascular diseases. The associations were estimated in models with mutual adjustment of body fat percentage and waist-to-height ratio. Models are stratified by region, age group, education, and ethnicity and adjusted for deprivation, smoking status, drinking status, physical activity, and body fat percentage. Vertical gray lines indicate the overall association. CI, confidence interval; HR, hazard ratio.

FIGURE 2

Subgroup analysis for sex-specific associations between waist-to-height ratio and ischemic cardiovascular diseases. The associations were estimated in models with mutual adjustment of body fat percentage and waist-to-height ratio. Models are stratified by region, age group, education, and ethnicity and adjusted for deprivation, smoking status, drinking status, physical activity, and body fat percentage. Vertical gray lines indicate the overall association. CI, confidence interval; HR, hazard ratio.

FIGURE 2

Subgroup analysis for sex-specific associations between waist-to-height ratio and ischemic cardiovascular diseases. The associations were estimated in models with mutual adjustment of body fat percentage and waist-to-height ratio. Models are stratified by region, age group, education, and ethnicity and adjusted for deprivation, smoking status, drinking status, physical activity, and body fat percentage. Vertical gray lines indicate the overall association. CI, confidence interval; HR, hazard ratio.