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Gait Speed in Older HIV Group Not Fast Enough to Cross Street Safely
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20th International AIDS Conference, July 20-25, 2014, Melbourne
Mark Mascolini
On average, older US HIV-positive adults with an undetectable viral load did not walk fast enough on a standard 8-foot walk test to cross streets safely, according to results of a 108-person study in North Carolina [1]. Findings on two other physical function tests indicated that these people did not meet criteria necessary to remain physically independent through their predicted life span.
More than half of HIV-positive people in the United States will be 50 or older in 2015, according to researchers from Duke University who conducted the physical function study. Much research shows signs of accelerated aging in people with HIV, but studies to date often include high proportions of white men and sometimes rely on self-report to gauge physical function.
To get a better idea of how physical function in older HIV-positive people compares with norms in an age- and gender-matched population, the Duke team focused on 108 people at least 50 years old who completed four standard tests. They also determined whether a person's nadir CD4 count affected their performance on these tests. Among 1820 HIV-positive people in active care at the clinic, 45% are 50 or older and 13% are 60 or older.
The 108 people in this analysis--all 50 or older--had taken a stable antiretroviral regimen for at least 6 months and had no viral loads above 200 copies in the past 12 months. The investigators excluded people with active substance abuse, current cardiovascular disease, neurologic problems affecting physical function, dementia or mental disorders preventing study participation, severe hearing or vision loss, or chronic pain that might limit test performance.
All study participants completed four tests: (1) 8-foot walk to measure gait speed, (2) 30-second chair stand to measure lower extremity strength, (3) grip strength to measure muscle function and strength, and (4) 6-minute walk test to measure aerobic endurance.
Participants averaged 60.3 years in age (range 50.2 to 78.1) and 28.6 kg/m2 in body mass index (range 17.4 to 51.2), putting the group in the overweight range. Time since HIV diagnosis averaged 15.3 years (range 1.4 to 31.7), and current CD4 count averaged 691 (range 83 to 2096). Fifty-three people (49%) were 50 to 59 years old, 49 (45%) were 60 to 69, and 6 (6%) were 70 or older. The group included 76 men (70%) and 32 women; 64 (59%) were black, 41 (38%) white, and 3 (3%) Hispanic.
Results of all four tests indicated diminished performance compared with normal reference ranges for healthy older adults matched by age and gender:
Weighted difference from healthy population norms
-- 8-foot walk test, gait speed, usual speed (m/sec): -0.20 +/- 0.25
-- 8-foot walk test, gait speed, maximal speed (m/sec): -0.21 +/- 0.37
-- 30-second chair stand, lower extremity strength (sec): -1.11 +/- 4.06
-- Grip strength (kg): -3.89 +/- 8.89
-- 6-minute walk distance, aerobic endurance (m): -105.15 +/- 100.93
Nadir CD4 count had no association with physical function as measured by any of the tests.
The Duke team determined that for people over 50 years old, a gait speed difference greater than 0.1 meter/second on the 8-foot walk test can be considered clinically meaningful. They figured that the average usual gait speed of these study participants means they walked more slowly than necessary to cross a street safely.
For the 6-minute walk test, the investigators determined that a difference greater than 50 meters can be considered clinically meaningful for people over 50. Walking an average 105.5 meters less in 6 minutes than the norm, the study group far surpassed this threshold of clinical significance. The Duke team figured that for the 6-minute walk test and the 30-second chair stand, participants did not meet criteria necessary to remain physically independent through their projected life span.
These findings are especially striking since all study participants had an undetectable viral load, and none had major comorbidities that might limit physical function. The researchers stressed the importance of determining whether older HIV-positive adults "have diminished physical performance in order to prevent future complications, such as falls or disability."
Reference
1. Lan A, Morey M, Chin T, et al. Diminished physical function in older HIV+ adults despite successful antiretroviral therapy. AIDS 2014. 20th International AIDS Conference. July 20-25, 2014. Melbourne. Abstract THPE056.
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