The functional ACTN3 577X variant increases the risk of falling in older females: results from two large independent cohort studies.

Background: Falls among elderly people is a major issue in public health, causing debilitating outcomes including fracture. The identification of genetic risk factors for falling may provide a strategy for effectively targeting falls prevention programs. We investigated whether a common functional variant of skeletal muscle α-actinin-3 (ACTN3 p. R577X) previously associated with impairments in muscle strength, power, and physical functioning represents a risk factor for falls.

Methods: Case-control analysis was conducted using two large cohorts of Caucasian postmenopausal women--the North of Scotland Osteoporosis Study (n = 1,245) and the Aberdeen Prospective Osteoporosis Screening Study (n = 2,918)--for whom self-reported falls status and DNA samples were available. Cross-sectional analysis of fallers versus nonfallers at baseline and follow-up was performed. In addition, individuals who reported having fallen at more than one timepoint (recurrent fallers) were compared with those who reported not falling at any timepoint.

Results: Association between R577X genotype and falls was identified and validated. Carriage of 577X (one or two copies) was significantly associated with a 33% (10%-61%) increased risk of falling, with the effect apparent at both baseline and follow-up assessments (meta-analysis p = .003 and p = .02, respectively). No significant effect on recurrent falls was observed.

Conclusion: This study reports for the first time that the functional ACTN3 R577X genotype represents a genetic risk factor for falling in older females.