Functional Vulnerability and Long-Term Mortality in Adults With Ankle-Brachial Index-Defined Peripheral Artery Disease: A NHANES Cohort Study

Functional limitations are common in peripheral artery disease (PAD), but the association of a brief self-reported functional-burden measure with objectively defined PAD and long-term mortality remains incompletely characterized.

We analyzed National Health and Nutrition Examination Survey 1999-2004 participants aged >=40 years with ankle-brachial index (ABI), physical functioning, and linked mortality data. PAD was defined as minimum ABI <=0.90. A NHANES-derived functional vulnerability index (NFVI; range 0-4) was constructed from difficulty walking a quarter mile, walking up ten steps, stooping/crouching/kneeling, and standing for long periods. NFVI was intended as a brief functional-burden measure rather than a diagnostic frailty instrument. Survey-weighted models evaluated PAD status, NFVI, and mortality, with validated modified cardiovascular health (mCVH) used for additional adjustment.

The PAD NFVI cohort included 462 participants and 375 deaths. PAD was associated with high NFVI after adjustment for sociodemographic factors and mCVH (OR 1.748, 95% CI 1.218-2.510; P=0.005). In PAD participants, each 1-point higher NFVI was associated with all-cause mortality after adjustment for sociodemographic factors and minimum ABI (HR 1.095, 95% CI 1.017-1.179; P=0.017). After additional mCVH adjustment, the continuous association was attenuated (HR 1.075, 95% CI 0.993-1.165; P=0.075), whereas high NFVI remained associated with mortality (HR 1.346, 95% CI 1.026-1.767; P=0.032). Complete-case selection was substantial (462/647 PAD participants), with marked differences between included and excluded participants, particularly in age, potentially limiting generalizability.

Functional vulnerability was more common among adults with ABI-defined PAD and was associated with long-term all-cause mortality. These findings demonstrate an epidemiologic association rather than the clinical utility, validation, or incremental prognostic value of NFVI and do not establish a clinically meaningful NFVI mortality threshold. Prospective PAD-specific validation and comparison with established frailty measures are required before clinical use.