Background We have previously shown that hip fracture rates in Norway declined from the 1990s through 2013. During the past decades, the number of people who are living with a total hip replacement has increased. We aimed to investigate whether hip fracture rates continued to decline after 2013, and whether the increase in total hip replacements have impacted on the decline, assuming that living with a total hip prosthesis precludes fracture of the hip concerned.
Methods All hospital stays with a hip fracture in Norway 1999–2019 are available in the Norwegian Epidemiologic Osteoporosis Studies (NOREPOS) hip fracture database. Population size according to sex and 1-year age groups are available in official population tables from Statistics Norway. Primary total hip replacements (for any cause except acute hip fracture and sequela after hip fracture) 1989–2019 were obtained from The Norwegian Arthroplasty Register (NAR). We calculated the annual age-standardised incidence rates of hip fracture by sex for the period 1999–2019. The hip fracture rates in a scenario with no hip prostheses were calculated by subtracting 0.5 persons from the population at risk for each prevalent hip prosthesis, considering that each person has two hips at risk of fracture. We calculated the difference between the observed and expected number of hip fractures in 2019, given unchanged fracture rates since 1999, and estimated how much of the decline could be attributed to the increased prevalence of hip prostheses.
Results From 1999 to 2019, age-standardised incidence rates decreased by 27% in women and 20% in men. The rates remained stable in those under 70 years and decreased in those 70 and above. Excluding replaced hips from the population at risk led to higher incidence rates, and this impact was considerably greater at higher ages. For women and men above 80 years, hip fracture rates in 2019 increased by 13% and 7%, respectively, after excluding prevalent hip prostheses from the population at risk. The increased prevalence of hip prostheses over the period accounted for approximately 18% (11% in men and 20% in women) of the observed decline in hip fracture rates.
Conclusion The incidence of hip fractures in Norway declined between 1999 and 2019. The increasing number of people living with hip prostheses may have significantly contributed to the observed declining time trends in incidence of hip fractures, particularly in the older age groups.
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