Secular trends of hip fractures in France: impact of changing characteristics of the background population.

Hip fractures are a societal burden because of their high morbidity and mortality and the cost they generate. With the aging of the population, worries grow about an increase of the incidence and incidence rate of hip fracture in the future. Controversial data have been provided in relation to the referencepopulation used. The aim of this study was to assess the impact of the choice of the reference population in the incidence rate of hip fracture. Data were extracted from the French National Hospital Database related to the hospitalizations for hip fracture in France between 2002 and 2013 in patients over 59 years and were classified by gender and age (59-74, 75-84, over 84 years, over 59 years). The crude incidence rates of hip fracture were calculated by dividing the number of hospitalizations for hip fracture by the corresponding populations. To assess the impact of the choice of the reference population, we then calculated the adjusted incidence rates using direct standardization on age for the 2013 reference population. From 2002 to 2013, the incidence of hip fracture rose by 4.8% in women (from 49,287 to 51,661) and 21.8% in men (from 12,716 to 15,482) aged over 59 years. Meanwhile, French population over 59 years increased more with a rise of 21.3% in women and 28.7% in men, resulting in a decrease in the crude incidence rates of 13.6% in women and 5.4% in men. However, this decrease was larger after direct standardization on the 2013 population of reference as 25.6% in women and 19.2% in men as a result of a difference in age-structure of the population. The incidence of hip fractures continues to grow despite a reduced incidence rate throughout a 12-year-period.