Figure 2. Differences in frailty-related factors according to serum kynurenine tertiles (A) before and (B) after adjusting for sex, age, and BMI. Frailty index is calculated based on the Rockwood’s proposal. The estimated means with 95% confidence intervals were generated and compared using analysis of covariance. Serum kynurenine tertiles: T1 = 0.78–1.52 μM, T2 = 1.53–2.01 μM, and T3 = 2.02–4.44 μM. * and † indicate statistically significant differences from T1 and T2 tertiles, respectively. Abbreviations: PHQ-2, patient health questionnaire-2; SPPB, short physical performance battery.