When CKM Syndrome Stage Is Not a Severity Scale: Audiometric Hearing Thresholds in Older U.S. Adults

Background: Cardiovascular, kidney, and metabolic conditions have each been associated with hearing outcomes, but little is known about whether cardiovascular-kidney-metabolic (CKM) syndrome staging tracks objective hearing sensitivity in older adults. Methods: We analyzed NHANES 2017-March 2020 pre-pandemic data for adults aged 70-79 years. CKM syndrome Stages 0-4 were operationalized from ascertainable domains of the 2026 AHA/ACC/ADA/ASN guideline, including HbA1c and design-valid fasting plasma glucose criteria for dysglycemia. The outcome was bilateral pure-tone average at 0.5, 1, 2, and 4 kHz (PTA4). Survey-weighted models adjusted for age, sex, race/ethnicity, education, smoking, and occupational and nonoccupational noise exposure. Results: The primary CKM syndrome stage analysis included 285 participants (Stage 0, n=1; Stage 1, n=18; Stage 2, n=103; Stage 3, n=65; Stage 4, n=98). The five-stage omnibus Wald test was statistically significant (F(4,25)=21.405, p=9.01e-8), but Stage 0 contained only one participant and the adjusted means were nonmonotonic (9.49, 24.3, 31.0, 29.0, and 33.4 dB HL). None of the planned Stage 2-4 contrasts remained significant after Holm adjustment, and a Stage 2-4-only robustness analysis did not support overall heterogeneity (p=0.197). Waist circumference was the only one of nine continuous CKM-related measures retained after the nine-test Holm adjustment: bilateral PTA4 was 1.57 dB HL higher per 10 cm greater waist circumference (95% CI, 0.74-2.39; adjusted p=0.00547). A post-hoc spline diagnostic did not show clear evidence of nonlinearity (p=0.128). Five-stage component-by-stage interaction models were not estimable because Stage 0 contained a single participant; among Stages 2-4, none of six primary interaction tests met the Holm-adjusted threshold. Conclusions: The primary hypothesis of progressively poorer hearing with advancing CKM syndrome stage was not supported. Although the five-stage omnibus test was statistically significant, its interpretation was constrained by the single-participant Stage 0 category; analyses restricted to Stages 2-4 did not support a progressive stage pattern. Waist circumference showed a small secondary association with PTA4 after multiplicity adjustment, but its individual-level clinical significance remains uncertain.