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. 2009 Mar 24;53(12):1056-62.
doi: 10.1016/j.jacc.2008.09.063.

Associations of borderline and low normal ankle-brachial index values with functional decline at 5-year follow-up: the WALCS (Walking and Leg Circulation Study)

Mary M McDermott  1 , Jack M Guralnik, Lu Tian, Kiang Liu, Luigi Ferrucci, Yihua Liao, Leena Sharma, Michael H Criqui
Affiliations

Associations of borderline and low normal ankle-brachial index values with functional decline at 5-year follow-up: the WALCS (Walking and Leg Circulation Study)

Mary M McDermott et al. J Am Coll Cardiol. .

Abstract

Objectives: We studied associations of borderline and low normal ankle-brachial index (ABI) values with functional decline over a 5-year follow-up.

Background: The associations of borderline and low normal ABI with functional decline are unknown.

Methods: The 666 participants included 412 with peripheral arterial disease (PAD). Participants were categorized as follows: severe PAD (ABI <0.50), moderate PAD (ABI 0.50 to 0.69), mild PAD (ABI 0.70 to 0.89), borderline ABI (0.90 to 0.99), low normal ABI (1.00 to 1.09), and normal ABI (ABI 1.10 to 1.30). Outcomes were assessed annually for 5 years. Mobility loss was defined as loss of the ability to walk one-quarter mile or walk up and down 1 flight of stairs without assistance among participants without baseline mobility impairment. Becoming unable to walk for 6 min continuously was defined as stopping during the 6-min walk at follow-up among those who walked for 6 min continuously at baseline. Results were adjusted for age, sex, race, comorbidities, and other confounders.

Results: Hazard ratios (HRs) for mobility loss according to ABI category were as follows: severe PAD, HR: 4.16 (95% confidence interval [CI]: 1.58 to 10.92); moderate PAD, HR: 3.82 (95% CI: 1.66 to 8.81); mild PAD, HR: 3.22 (95% CI: 1.43 to 7.21); borderline ABI, HR: 3.07 (95% CI: 1.21 to 7.84); and low normal ABI, HR: 2.61 (95% CI: 1.08 to 6.32; p trend = 0.0018). Similar associations were observed for becoming unable to walk for 6 min continuously (p trend < 0.0001).

Conclusions: At 5-year follow-up, persons with borderline ABI values have a higher incidence of mobility loss and becoming unable to walk for 6 min continuously compared with persons who have a normal baseline ABI. A low normal ABI is associated with an increased incidence of mobility loss compared with persons who have a normal ABI.

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Figures

Figure 1
Figure 1
Adjusted associations of baseline ankle brachial index and mobility loss at five year follow-up among persons age 55 and older (n=631) Results are adjusted for age, sex, race, comorbidities, body mass index, smoking, and physical activity levels. The ‘y’ axis shows the hazard ratio representing the risk of mobility loss at five year follow-up. Number of events per ankle brachial index (ABI) category: ABI <0.50: 12; ABI 0.50-0.69: 30; ABI 0.70-0.89: 30; ABI 0.90-99: 11; ABI 1.00-1.09: 16; ABI 1.10-1.30: 8. Number of deaths per ankle brachial index (ABI) category: ABI <0.50: 20; ABI 0.50-0.69: 39; ABI 0.70-0.89: 28; ABI 0.90-99: 8; ABI 1.00-1.09: 9; ABI 1.10-1.30: 10.
Figure 2
Figure 2
Adjusted associations of baseline ankle brachial index and loss of the ability to walk continuously for six minutes at five year follow-up among persons age 55 and older (n=276). Results are adjusted for age, sex, race, comorbidities, body mass index, smoking, and physical activity levels. The ‘y’ axis shows the hazard ratio representing risk of becoming unable to walk continuously for six minutes at five year follow-up. Excludes participants with knee arthritis, hip arthritis, spinal stenosis, and disk disease because of a significant interaction between the presence vs. absence of lower extremity arthritis and spinal disk disease and the association of the ankle brachial index with becoming unable to walk for six-minutes continuously. ABI <0.50: 12; ABI 0.50-0.69: 19; ABI 0.70-0.89: 15; ABI 0.90-99: 4; ABI 1.00-1.09: 4; ABI 1.10-1.30: 3 Number of deaths per ABI category: ABI <0.50: 4; ABI 0.50-0.69: 21; ABI 0.70-0.89: 28; ABI 0.90-99: 8; ABI 1.00-1.09: 9; ABI 1.10-1.30: 10.
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