Comparison of novel and traditional anthropometric indices: which is the best indicator of frailty in older adults?

BACKGROUND: Frailty is a critical geriatric syndrome associated with adverse health outcomes and exhibits a complex relationship with obesity. Traditional anthropometrics, such as body mass index (BMI), inadequately assess obesity-related risks in the aging population. Emerging indices better capture visceral adiposity, potentially enhancing frailty prediction. This study evaluates these indices' associations with frailty in older adults. METHODS: This study analyzed existing data collected between 2002 and 2007 as part of the National Health and Nutrition Examination Survey (NHANES). BMI, body roundness index (BRI), a body shape index (ABSI), waist-to-height ratio (WHtR), and waist/height0.5 (WHT·5R) were calculated using waist circumference, weight, and height. We used a modified frailty index (FI) with 36 standardized parameters to quantify the severity of frailty by the cumulative proportion of deficits. RESULTS: In the adjusted model, increases in all indices except ABSI were statistically significantly associated with increases in FI (BRI: β(95%CI) = 0.004(0.003, 0.005); BMI: β(95%CI) = 0.001(0.0001, 0.001); ABSI: β(95%CI) = 2.034(1.627, 2.440); WHtR: β(95%CI) = 0.093(0.067, 0.119); WHT·5R: β(95%CI) = 0.007(0.005,0.009)). Bootstrap analysis showed that BRI had a greater impact on FI than BMI (difference = 0.0019), while WHtR and WHT·5R had a stronger impact on FI than BRI (difference = -0.0746 and -0.0027, respectively). The effect of WHtR on FI was significantly higher than that of WHT·5R (difference = 0.0719). CONCLUSION: This study highlighted that WHtR was more strongly associated with FI than BMI, BRI, and WHT·5R, and highlighted the priority of waist-centered obesity measures in frailty risk assessment and clinical intervention in the elderly.