Baseline functional performance predicts the rate of mobility loss in persons with peripheral arterial disease

Abstract

Objectives: We compared rates of mobility loss among persons with versus without peripheral arterial disease (PAD). Associations between baseline functional performance and mobility loss in persons with and without PAD were studied.

Background: Persons with PAD have poorer functional performance than persons without PAD. The prognostic value of poorer performance in persons with PAD is unknown.

Methods: Participants were 398 persons with and 240 without PAD who were free of mobility impairment at baseline. Participants were followed for a median of 50 months. Baseline measures included the 6-min walk and the Short Physical Performance Battery score. Mobility status, assessed annually, was defined as the self-reported loss of the ability to walk one-quarter mile or walk up and down one flight of stairs without assistance.

Results: Adjusting for age and gender, we found that PAD participants had a greater rate of mobility loss than persons without PAD (hazard ratio [HR] 1.63; 95% confidence interval [CI] 1.03 to 2.56). This difference was not statistically significant after additional adjustment for baseline performance. Among PAD participants, risk of mobility loss in the lowest versus the 2 highest quartiles of baseline performance were as follows: HR 9.65 (95% CI 3.35 to 27.77, p < 0.001) for the 6-min walk and HR 12.84 (95% CI 4.64 to 35.55, p < 0.001) for the Short Physical Performance Battery when adjusting for confounders.

Conclusions: Persons with PAD experience greater mobility loss than persons without PAD. This association was explained by poorer baseline functional performance among participants with PAD. Poorer lower extremity performance predicts increased mobility loss in persons with and without PAD.

Figure 1. Hazard Ratios for Mobility Loss at 50-Month Follow-Up Among Men and Women With PAD, According to Baseline Functional Performance

Model 1: adjusts for age, gender, race, ankle-brachial index, body mass index, pack-years of cigarette smoking, leg symptoms, walking exercise frequency, and comorbidities. Model 2: Adjusts for variables in model 1 and blocks walked for exercise. Categories of performance: 6-min walk = Category 1 (lowest quartile): ≤1,001 ft; Category 2 (second quartile): 1,001 to ≤1,304 ft; Category 3 (third and fourth quartiles combined): >1,304 ft. 4-m walk (usual pace) = Category 1 (lowest quartile): ≤0.792 m/s; Category 2 (second quartile): 0.792 to ≤0.915 m/s; Category 3 (third and fourth quartiles combined): >0.915 m/s. 4-m walk (fast pace) = Category 1 (lowest quartile): ≤1.078 m/s; Category 2 (second quartile): 1.078 to ≤1.274 m/s; Category 3 (third and fourth quartiles combined): >1.274 m/s. Short Physical Performance Battery (0 to 12 scale, 12 = best) = Category 1: 1 to 8; Category 2: 9 to 10; Category 3: 11 to 12. *p < 0.01 relative to the highest 2 categories **p < 0.05 relative to the highest 2 categories. PAD = peripheral arterial disease.

Figure 2. Hazard Ratios for Mobility Loss at 50-Month Follow-Up Among Men and Women Without PAD, According to Baseline Functional Performance

Model 1: adjusts for age, gender, race, body mass index, pack-years of cigarette smoking, walking exercise frequency, and comorbidities. Model 2: adjusts for variables in model 1 and blocks walked for exercise. Categories of performance: 6-min walk = Category 1 (lowest quartile): ≤1,001 ft; Category 2 (second quartile): 1,001 to ≤1,304 ft; Category 3 (third and fourth quartiles combined): >1,304 ft. 4-m walk (usual pace) = Category 1 (lowest quartile): ≤0.792 m/s; Category 2 (second quartile): 0.797 to ≤0.915 m/s; Category 3 (third and fourth quartiles combined): >0.915 m/s. 4-m walk (fast pace) = Category 1 (lowest quartile): ≤1.078 m/s; Category 2 (second quartile): 1.078 to ≤1.274 m/s; Category 3 (third and fourth quartiles combined): >1.274 m/s. Short Physical Performance Battery (0 to 12 scale, 12 = best) = Category 1: 1 to 8; Category 2: 9 to 10; Category 3: 11 to 12. *p < 0.05 relative to the highest 2 quartiles; **p < 0.001 relative to the highest 2 quartiles. PAD = peripheral arterial disease.

Figure 3. Rates of Mobility Loss for Participants With and Without PAD, According to Baseline Functional Performance Categories Defined for the Entire Cohort

Categories of performance: 6-min walk = Category 1 (lowest quartile): ≤1,001 ft; Category 2 (second quartile): 1,001 to ≤1,304 ft; Category 3 (third and fourth quartiles combined): >1,304 ft. 4-m walk (usual pace) = Category 1 (lowest quartile): ≤0.792 m/s; Category 2 (second quartile): 0.792 to ≤0.915 m/s; Category 3 (third and fourth quartiles combined): >0.915 m/s. 4-m walk (fast pace) = Category 1 (lowest quartile): ≤1.078 m/s; Category 2 (second quartile): 1.078 to ≤1.274 m/s; Category 3 (third and fourth quartiles combined): >1.274 m/s. Short Physical Performance Battery (0 to 12 scale, 12 = best) = Category 1: 1 to 8; Category 2: 9 to 10; Category 3: 11 to 12. PAD = peripheral arterial disease.