Familial resemblance and shared latent familial variance in recurrent fall risk in older women.

BACKGROUND A possible familial component to fracture risk may be mediated through a genetic liability to fall recurrently. METHODS Our analysis sample included 186 female sibling-ships (n=401) of mean age 71.9 yr (SD=5.0). Using variance component models, we estimated residual upper-limit heritabilities in fall-risk mobility phenotypes (e.g., chair-stand time, rapid step-ups, and usual-paced walking speed) and in recurrent falls. We also estimated familial and environmental (unmeasured) correlations between pairs of fall-risk mobility phenotypes. All models were adjusted for age, height, body mass index, and medical and environmental factors. RESULTS Residual upper-limit heritabilities were all moderate (P<0.05), ranging from 0.27 for usual-paced walking speed to 0.58 for recurrent falls. A strong familial correlation between usual-paced walking speed and rapid step-ups of 0.65 (P<0.01) was identified. Familial correlations between usual-paced walking speed and chair-stand time (-0.02) and between chair-stand time and rapid step-ups (-0.27) were both nonsignificant (P>0.05). Environmental correlations ranged from 0.35 to 0.58 (absolute values), P<0.05 for all. CONCLUSIONS There exists moderate familial resemblance in fall-risk mobility phenotypes and recurrent falls among older female siblings, which we expect is primarily genetic given that adult siblings live separate lives. All fall-risk mobility phenotypes may be coinfluenced at least to a small degree by shared latent familial or environmental factors; however, up to approximately one-half of the covariation between usual-paced walking speed and rapid step-ups may be due to a common set of genes.