2012 Annual Conference

QUIBEN, MYLA

University of Texas Health Science Center at San Antonio; San Antonio, TX

Walking speed (WS) is an established outcome measure for function and mobility, and a powerful predictor of health status and functional decline. While normative data for sex and age strata have been published, no study has examined possible ethnic differences in WS or the applicability of existing WS norms across ethnic groups. The purpose of this study was to determine whether WS differs between community-dwelling Mexican American (MA) and European American (EA) male and female older adults. 

WS was analyzed in 703 older adults (aged 65-80 years), comprised of 366 MAs and 377 EAs who participated in the San Antonio Longitudinal Study of Aging (SALSA), a community-based study of the disablement process. 

Participants were given a comprehensive home-based assessment conducted in the participant’s home and a performance-based assessment conducted at the University’s clinical research center (CRC). WS was measured as part of the CRC performance-based assessments.  Participants were asked to complete two 15 meter (50 feet) walks with a short break in between. Each trial began from a standing start and participants were asked to walk at a usual and comfortable pace. Time to complete the walks was measured with a stopwatch by trained examiners using standardized instructions. The two trials were averaged and WS was calculated as distance (meters) divided by time (seconds).

Sex and ethnic differences in WS were analyzed using two-way ANOVA.  Because sex and ethnic variations in height may account for observed differences in WS, a two-way ANCOVA was also performed with height as a covariate. All analyses were performed with SPSS 20.

EAs walked significantly faster than MAs (mean speed 1.22 m/s vs. 1.09 m/s, respectively; p<0.001), and males in both ethnic groups walked significantly faster than females (MA Males: 1.15 m/s, Female: 1.04 m/s; EA Males: 1.28 m/s Females: 1.18m/s; sex main effect: p=0.02) There was no significant ethnic-sex interaction effect. MAs of both sexes were significantly shorter than EAs (Males: 66.1 vs. 68.7 in.; Females: 60.3 vs. 63.4 in.). After adjustment for height, the ethnic difference in walking speed was no longer statistically significant (p=0.52), but interestingly, females in both ethnic groups walked significantly faster than males (MA Females: 1.17 m/s, Males: 1.07 m/s; EA Females: 1.21 m/s Males: 1.09 m/s; sex main effect, p=0.03). 

Ethnic differences in WS between older MAs and EAs were explained by corresponding differences in height. While females had slower WS compared with males in unadjusted comparisons, after adjusting for height, females of both ethnic groups had faster WS than their male counterparts. Overall, height accounted for 4.1% of the variance in WS in this bi-ethnic community-dwelling cohort of older MAs and EAs, after accounting for the variance in WS explained by ethnic group and sex (adjusted R2 = 3.3%).

To appropriately assess the clinical implications of WS, it may be necessary to utilize ethnic and/or sex-specific norms or cut-points that adjust for height.