Functional Capacity and Functional Performance in Peripheral Arterial Disease: A Multigroup Analysis.

Abstract

Older adults with peripheral arterial disease (PAD) can experience impairments in both functional capacity (FC) and functional performance (FP). Few studies have examined the effect of PAD severity on FC and FP utilizing a latent variable model. The purpose of this secondary analysis of the National Health and Nutrition Examination Survey (NHANES) 1999 – 2002 survey cycles was to develop and test a latent variable model of FC and FP in older adults with and without PAD. The study sample included a subpopulation of all NHANES participants from the 1999-2002 survey cycles (N = 21,004) over the age of 50 years (n = 3695) who had screening performed for PAD. Subjects were then separated into a ‘no PAD’ (n = 3317) and ‘PAD’ (n = 378) group for analysis. Measures included ankle-brachial index (PAD severity), maximum calf circumference, quadriceps strength (lower extremity strength), Semmes-Weinstein monofilament test (lower extremity sensory impairment), 20-foot timed walk (usual gait speed), self-reported level of physical activity, and physical function questionnaire (ability to perform routine daily tasks). Analyses included multigroup confirmatory factor analysis (MG-CFA) of the measurement model, structural equation modeling, and indirect effect testing. The MG-CFA of the measurement model demonstrated configural, metric, and scalar invariance between the ‘no PAD’ and ‘PAD’ groups. Multigroup structural equation modeling demonstrated acceptable fit of the model to the data controlling for PAD severity, age, and gender (RMSEA 0.058, CFI 0.811, and SRMR 0.069). The fit was also acceptable after controlling for PAD severity, age, gender, and diabetes (RMSEA 0.059, CFI 0.782, and SRMR 0.069). Indirect effect testing showed FC to mediate the relationship between PAD severity and FP in the ‘PAD’ group. These findings support the applicability of a latent variable model for evaluating the effect of PAD severity on FC and FP in older adults with PAD.