Explaining the declining hip fracture incidence in Denmark 1999-2018. The Hip-IMPACT model

Abstract Background Age-specific incidence rates of hip fractures have declined in many countries, yet the future fracture burden may increase dramatically due to the ageing population unless preventive efforts are intensified. We quantified the contributions of changes in osteoporosis treatment and population risk factors to the observed time trends in hip fracture rates in Denmark during 1999-2018. Methods Based on the IMPACT coronary heart disease model, we have previously developed the Hip-IMPACT model with hip fracture incidence as outcome, applying the principle of population attributable fractions. The model was based on Danish incidence rates of hip fractures, medication uptake and prevalence of established lifestyle risk factors in sex- and five-year age groups (50 to 90+ years) in 1999 and 2018. Results Hip fracture rates declined by 39% from 1999 to 2018, corresponding to a difference between expected and observed number hip fractures in 2018 of 6012. There was an increase in uptake of anti-osteoporosis treatment during the period which explained 15% of the decline in fracture rates, of which alendronate accounted for the majority. Use of fall risk-increasing hypnotics (benzodiazepines and Z drugs) declined; this change explained 28% of the decline in hip fracture rates. Use of opioids increased and had a net negative impact, while glucocorticoid use was relatively stable. Increased prevalence of people living with total hip arthroplasty for osteoarthritis explained 7%, higher physical activity explained 4%, and increased body mass index explained 9% of the decline. Conclusions In our preliminary analyses, approximately half of the observed decline in hip fracture rates in Denmark from 1999 to 2018 could be attributed to increased uptake of anti-osteoporosis medications, reduced use of fall risk-increasing drugs (hypnotics), and changes in population risk factors such as increases in body mass index, physical activity, and prevalence of hip arthroplasty. Key messages • Knowledge about the drivers of the observed time trends in incidence rates of hip fracture may help identify missed opportunities for prevention and inform public health policy. • The relatively low contribution of uptake of anti-osteoporosis drugs to the observed decline over time in hip fracture incidence suggests an unfulfilled preventive potential of osteoporosis treatment.