Waist-to-Height Ratio Identifies Cardiometabolic Risk Not Captured by Body Mass Index: The All of Us Research Program
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Background
Body mass index (BMI) does not characterize central adiposity and may obscure cardiometabolic risk among adults classified as normal weight. We evaluated associations between waist-to-height ratio (WHtR) and incident disease across the BMI spectrum and among adults with normal BMI.
Methods
We studied 308,600 adults in the All of Us Research Program. Participants with the corresponding prevalent disease were excluded separately for eight cardiometabolic outcomes. Cause-specific Cox models adjusted for demographic, socioeconomic, smoking, and BMI-related factors. We evaluated continuous and nonlinear WHtR associations, elevated WHtR among normal-BMI adults, and incremental discrimination. Additional analyses tested WHtR-by-BMI-category interactions.
Results
Among 77,684 adults with normal BMI, 24,301 (31.3%) had WHtR ≥0.50. In whole-cohort analyses, adjusted hazard ratios (HRs) per 0.05 higher WHtR ranged from 1.07 to 1.31 across the eight outcomes. In BMI-stratified interaction models, corresponding diabetes HRs were 1.52 (95% CI, 1.43–1.61) in normal BMI, 1.42 (1.36–1.49) in overweight, and 1.22 (1.20–1.25) in obesity (P for interaction <0.001). Hypertension associations also differed across BMI groups (P for interaction <0.001). Among normal-BMI adults, WHtR ≥0.50 versus <0.50 was associated with diabetes (HR, 1.74), myocardial infarction (1.49), and ischemic stroke (1.52). Associations with all eight outcomes persisted in normal-BMI landmark analyses excluding the first year. Flexible age adjustment preserved the principal findings. Adding nonlinear WHtR improved cross-validated discrimination, most notably for diabetes (ΔC-index=0.0134).
Conclusions
WHtR identified cardiometabolic risk beyond BMI classification. Associations with diabetes and hypertension were particularly pronounced among normal-BMI adults, supporting assessment of central adiposity alongside BMI.
Clinical Perspective
What Is New?
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In this longitudinal cohort of 308,600 adults, higher waist-to-height ratio (WHtR) was associated with incident type 2 diabetes, hypertension, ischemic heart disease, myocardial infarction, ischemic stroke, heart failure, atrial fibrillation, and chronic kidney disease independently of body mass index (BMI).
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Among adults with normal BMI, 31.3% had WHtR ≥0.50, identifying a phenotype associated with higher incidence of all eight evaluated cardiometabolic outcomes. These associations persisted after excluding the first year of follow-up.
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The association between continuous WHtR and incident diabetes was stronger among adults with normal BMI than among those with obesity. For hypertension, the association was stronger in normal-BMI adults than in both overweight and obesity.
What Are the Clinical Implications?
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BMI alone can miss clinically relevant central adiposity and associated cardiometabolic risk among adults classified as having normal weight.
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WHtR is a practical complementary measure that clinicians may consider alongside BMI during preventive cardiometabolic assessment, particularly when a patient has a normal BMI but other risk factors or clinical concerns.
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WHtR should not be treated as a stand-alone risk model or a universal treatment threshold; its incremental prognostic value and exposure-response patterns differed by outcome.
