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Gait Speed Slows More With Age in MACS Men With Than Without HIV
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5th International Workshop on HIV and Aging. October 20-21, 2014. Baltimore
Mark Mascolini
Gait speed, a marker of biological aging, was slower in HIV-positive than HIV-negative men over 40 in the Multicenter AIDS Cohort Study (MACS) [1]. And gait speed slowed faster with age in HIV-positive men than in their HIV-negative cohort counterparts.
Data from the Baltimore Longitudinal Study of Aging indicate that gait speed starts to decline around age 40 in the general population, with a steeper drop after age 60 [2]. Research also shows that slowed gait speed predicts functional decline and disability, and pooled analysis of 9 cohort studies linked gait to survival in older adults [3].
Studies of frailty in HIV populations often include 6-minute walk distance and 400-meter walk time, Johns Hopkins investigators who conducted the MACS analysis observed. But most such studies are cross-sectional, involve small and younger populations, and lack a control group. To assess gait speed in HIV-positive gay/bisexual men in MACS and HIV-negative MACS members, these researchers scrutinized MACS functional assessment data collected from 2007 through 2013.
The analysis focused on 973 HIV-positive men and 1052 men without HIV. Average age at the 2007 baseline visit was younger in the HIV group (48.7 versus 52.1, P < 0.001), and body mass index was lower in men with HIV (25.5 versus 27.3 kg/m2, P < 0.001). The HIV group included a higher proportion of nonwhites (39.8% versus 24.6%, P < 0.001) and a higher proportion who reported drug use (49.8% versus 43.4%, P = 0.004). The HIV contingent also had higher proportions with HBV infection (4.1% versus under 1%, P < 0.001) and HCV infection (15.5% versus 8.9%, P < 0.001).
Average baseline gait speed at age 50 was significantly slower among men with HIV than in the HIV-negative group (1.19 versus 1.24 m/sec, P < 0.001). Among men in their early and mid-40s, 95% confidence intervals around usual gait speed overlapped in those with and without HIV. Starting in the late 40s, though, the curves describing declining gait speed diverged in the HIV-positive and negative groups, with an accelerating decline among men infected with HIV. Yearly rate of declining gait speed was significantly greater in men with than without HIV (-0.03 m/sec per year).
Among all men 40 or older, variables independently associated with slower gait speed included HIV infection (coefficient -0.027, P < 0.001), older age (coefficient -0.009, P < 0.001), and the interaction of HIV infection and age (coefficient -0.002, P = 0.007). The last association indicates that men with HIV tended to walk more slowly with advancing age than did men without HIV.
When the investigators analyzed the association between age and usual gait speed separately in men with and without HIV, they linked older age, lower weight, and nonwhite race to slower gait speed in both groups of men. In the HIV group, higher nadir CD4 count was associated with faster gait speed, and in the HIV-negative group, HCV infection significantly predicted slower gait speed. Greater height and more education were associated with faster gait speed in men with and without HIV.
Adjusted analysis indicated that men with HIV had a 57% higher risk of gait speed below 1.0 m/sec than men without HIV (adjusted hazard ratio 1.57, 95% confidence interval 1.29 to 1.92, P < 0.001).
The MACS team concluded that gait speed at age 50 is 0.05 m/sec slower with HIV than without HIV in this cohort. They characterized this finding as "evidence of a clinically meaningful difference [in gait speed] in middle age." The investigators proposed that "those aging with HIV may have a greater risk of future mobility limitations and subsequent disability" than men without HIV.
References
1. Schrack JA, Althoff KN, Erlandson KM, et al. Accelerated longitudinal gait speed decline in HIV-infected older adults. 5th International Workshop on HIV and Aging. October 20-21, 2014. Baltimore. Abstract 12.
2. Schrack JA, Simonsick EM, Chaves PH, Ferrucci L. The role of energetic cost in the age-related slowing of gait speed. J Am Geriatr Soc. 2012;60:1811-1816. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3470763/
3. Studenski S, Perera S, Patel K, et al. Gait speed and survival in older adults. JAMA. 2011;305:50-58. http://jama.jamanetwork.com/article.aspx?articleid=644554
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