A twin study on the heritability of walking ability among older women

Abstract

Background. This study examined the role of genetic and environmental factors explaining individual differences in women's walking ability in old age. Methods. A maximal walking speed test over 10 meters and a 6-minute walking endurance test were done under standard conditions among 92 monozygotic and 105 dizygotic pairs of twin sisters reared together, aged 63-75 years. Results. The mean maximum walking speed was 1.73 ± 0.32 m/s and the mean distance covered in the 6-minute walking test was 525.6 ± 77.3 m. Multivariate genetic modeling showed that a minor part of the variances in walking speed (16%, 95% confidence interval [CI]: 0%-54%) and endurance (20%, 95% CI: 0%-56%) were accounted for by genetic influences, and that the genetic influences were common to both traits. The corresponding proportions for common environmental factors were 37% (95% CI: 4%-58%) and 26% (95% CI: 0%-52%), and for individual environmental factors 46% (95% CI: 35%-59%) and 54% (95% CI 42%-68%), respectively. The environmental effects were partially common to both traits. Conclusions. Among relatively healthy older women, a modest portion of the variances of walking speed and endurance were accounted for by genetic factors, whereas shared and individual environmental factors explained most of the variance in both traits. Copyright 2006 by The Gerontological Society of America.