Falls incidence underestimates the risk of fall-related injuries in older age groups: a comparison with the FARE (Falls risk by Exposure)

Background: up till now, the risk of falls has been expressed as falls incidence (i.e. the number of falls or fallers per 100 person-years). However, the risk of an accident or injury is the probability of having an accident or injury per unit of exposure. The FARE ( Falls risk by Exposure) is a measure for falls risk which incorporates physical activity as a measure of exposure. The objective of this study was to compare falls incidence and the FARE when expressing the age-related risk of fall-related injuries. Methods: data of 21,020 community-dwelling elderly aged >= 55 years (60.3% women) obtained from a national survey (2000-05) were used to compare incidence of fall-related injuries and the FARE. In order to compare both measures, risk ratios (of both outcome measures) were calculated for each age group. Hierarchical regression analyses (linear versus exponential model) were conducted to check the best model fit when expressing falls risk by age for the total study population and for men and women separately. Results: the risk of fall-related injuries, calculated on the basis of the incidence of fall-related injuries, showed a linear relationship with age, whereas the risk calculated on the basis of fall-related injuries corrected for exposure (falls risk by exposure, FARE) showed an exponential relationship. Calculations on the basis of the incidence of fall-related injuries underestimated the risk of fall-related injuries in people aged 70 years and older, and especially in women. Conclusion: calculation of the risk of fall-related injuries based on the incidence of these injuries underestimates the risk of such injuries relative to that calculated on the basis of the FARE. FARE-based calculations enable the early identification of people at high risk of falls and provide a more sensitive outcome measure for studies evaluating falls prevention interventions.