Trends in Incidence of Hip Fracture and Hip Replacement in Denmark, 1996 to 2018.

Importance: The past several decades have witnessed substantial changes in treatments that are particularly relevant for older patients. Objectives: To assess changes in national-level incidence rates of fracture- and musculoskeletal-related (ie, arthritis-related) hip replacement procedures for individuals aged 40 to 104 years over a 23-year period in Denmark. Design, Setting, and Participants: This cohort study used national Danish health registers to include the Danish population aged 40 to 104 years from January 1, 1996, to December 31, 2018. Data were analyzed from May 31, 2022, to February 14, 2024. Main Outcomes and Measures: Age- and period-specific incidence rates of hip fracture and hip replacement stratified on fracture-related vs arthritis-related indication. Results: From 1996 to 2018, a total of 3 664 979 individuals were followed up for a mean (SD) of 14.6 (7.7) years, resulting in a follow-up time of 53 517 861 person-years and 158 982 (first) hip fractures, of which 42 825 involved fracture-related hip replacement procedures. A further 104 422 individuals underwent arthritis-related hip replacement. During the first 2 decades of the 21st century, hip fracture rates declined by 35% to 40% for individuals aged 70 to 104 years, and the proportion of the population undergoing fracture-related hip replacement increased by 50% to 70%, with modest variation across those aged 75 to 99 years. Rates of arthritis-related hip replacements peaked for individuals aged 75 to 79 years, but with the largest relative rate increase (75%-100%) occurring for those aged 80 to 94 years, primarily from 2001 to 2015, whereafter it remained nearly unchanged. The decline in rates of arthritis-related hip replacement after 75 to 79 years of age was gradual and did not suggest an upper age limit for access to arthritis-related hip replacement. Conclusions and Relevance: The findings of this cohort study suggest that during the past several decades in Denmark, the incidence of hip fractures declined by 35% to 40% among patients aged 80 to 104 years, while the proportion receiving fracture-related hip replacement remained relatively constant after 75 years of age. During the first decades of the 21st century, arthritis-related hip replacement incidence increased by 50% to 100% among older patients and stabilized hereafter, with no apparent cutoff age for this type of procedure. These patterns indicate a positive overall trend with declining hip fracture incidence over the last decades in Denmark, and the observed hip replacement incidence suggests that age is currently not a major determining factor guiding this type of surgery.