Every hour, two new forearm fractures and one new hip fracture occur in Norway. Hip fractures are painful, reduce function, shorten life expectancy, and entail large healthcare costs. Although the risk of hip fracture has declined during the past decades, an increase in the number of fractures is expected due to a growing elderly population. There are some well-established risk factors for fracture, but the question of why Norway is the world leader remains unresolved. We use national fracture data in combination with health studies and registries covering the total population of Norway to study factors considered important to reduce the number of fractures. The project has three work packages. In the first work package, we have developed a pioneer model for estimating the contribution of changes in risk factors and treatments over two decades to explain the decline in hip fracture incidence. The model was developed in collaboration with the University of Liverpool, based on their IMPACT model originally designed for cardiovascular disease. We found that two-thirds of the decline in hip fracture incidence from 1999 to 2019 could be explained by changes in risk factors such as body weight, smoking, and physical activity. Interestingly, we discovered that the increase in the number of individuals with total hip replacements, which prevent fractures in the operated hip, contributed substantially to the decline, especially among women. One-fifth of the decline could be attributed to increased use of osteoporosis medication during the period.
Secondly, there is an intriguing link between the immune system and bone metabolism. In a large sample from the general Norwegian population, we have found that the variation in tuberculin skin test responses after BCG vaccination as a measure of normal variation in immune function is related to long-term risk of hip fracture in men. Interestingly, no such clear association was observed in women. Based on these findings, we have contributed in further studies assessing the association between variation in immune function and other diseases (multiple sclerosis and osteoarthritis of the hip, respectively). Together with our collaborators, we have also investigated the association of dietary inflammatory pattern and fracture risk in the US Nurses’ Health Study.
In the third work package, we explore causes of geographic variations in fracture risk by combining data on weather conditions, climate changes, topography, and air pollution with individual-level sociodemographic and fracture outcome data. For example, we have found a clear increase in the risk of forearm fractures at cold ambient temperatures, especially at temperatures around the freezing point. The corresponding association was somewhat weaker for hip fractures, although there was still and increasing risk at low temperatures. Additionally, excess post–hip fracture mortality was found at cold ambient temperatures. There also seems to be a somewhat higher risk of forearm and hip fractures in both women and men at high levels of air pollution in Norway, and the risk seems to be highest among the thinnest.
The research is conducted by NOREPOS (the Norwegian Epidemiologic Osteoporosis Studies), a longstanding national research network comprising the four medical faculties in Norway and the Norwegian Institute of Public Health.
To postdoktorer og en midlertidig forsker har vært tilknyttet prosjektet. De to postdoktorene har kvalifisert seg til videre vitenskapelig arbeid ved omfattende analyser av data, publisering, vitenskapelig og populærvitenskapelig formidling, undervisning og veiledning, samt forskningsopphold hos internasjonale samarbeidspartnere. Forskeren har i kjølvannet av prosjektet fått fast stilling som førsteamanuensis ved Universitetet i Oslo, og vil ha videreføring av prosjektet som sitt forskningsfokus. Vi har etablert flere vitenskapelige samarbeid, knyttet studenter til prosjektet, og søkt om videre finansiering fra EU. I tillegg har vi gjennom prosjektperioden blitt involvert i det EU-finansierte European Health Data & Evidence Network (EHDEN)-samarbeidet. Prosjektets utstrakte nasjonale og internasjonale samarbeid har hatt stor betydning for prosjektets gjennomføring, kvalitet og virkninger. Det internasjonale samarbeidet har bidratt til videreutvikling og internasjonalisering av vår forskning og etablert fremtidige samarbeidsarenaer.
I arbeidspakke 1 har vi utviklet en ny modell, Hip-IMPACT, i samarbeid med University of Liverpool, og vi planlegger nå å applisere modellen på nasjonale danske data sammen med våre samarbeidspartnere ved Syddansk universitet. Selv om risiko for hoftebrudd for den enkelte har gått ned over tid, vil antall hoftebrudd øke i fremtiden, og det må tas grep for å bremse utviklingen. Modellen gir oss samlet kunnskap om hvor mye ulike årsaker har bidratt til nedgangen i risiko. Slik kunnskap gjør det mulig for beslutningstakere å identifisere hvilke faktorer som har hatt stor innflytelse på forebygging, og hvor forebyggingspotensialet er underutnyttet.
I arbeidspakke 2 har vi benyttet resultater fra tuberkulintest etter BCG-vaksine i masseundersøkelser for å studere normalvariasjon i immunrespons, og dens sammenheng med bruddrisiko flere tiår senere. Dette var et nyskapende eksempel på å benytte eksisterende befolkningsdata for å undersøke mulige uutforskede forklaringsfaktorer for utvikling av sykdom. Basert på denne studien har vi videre bidratt til studier som har undersøkt betydning av normalvariasjon i immunfunksjon for andre tilstander (multippel sklerose og hofteartrose).
I arbeidspakke 3 har vi etablert en database med klima- og miljømålinger som kan utvides for videre å besvare relaterte forskningsspørsmål, og for framtidig forskning på brudd eller andre helseutfall. Studier av betydning for temperatursvingninger for risiko for ulike typer brudd gjøres i samarbeid med Meteorologisk Institutt, og kan danne grunnlag for føre- og broddevarsel på yr.no.
Gjennom prosjektperioden har vi produsert relevant kunnskap, både deskriptiv og analytisk, som inngår i det samlede kunnskapsgrunnlaget som kunnskapsstøtte for forebygging av osteoporose og brudd som folkehelseproblem
Every year, more than 9000 Norwegians suffer a hip fracture. A decline in age-specific incidence has been observed. However, fracture burden is projected to increase due to an ageing population. The current project is organized into three work packages (WPs), intended to give novel and comprehensive information on an old public health problem that has long remained unresolved. We will use our national database of hip fractures (NORHip) in combination with health studies and registers covering the entire Norwegian population. New methodological approaches will be applied.
In WP1 we develope a pioneer model (named Hip-IMPACT) for estimating the contribution of changes in risk factors and treatments to explain the decline in hip fracture incidence. In collaboration with the University of Liverpool this is a further development of their IMPACT model originally developed for cardiovascular disease mortality.
The basis for WP2 is the connection between immune function and bone metabolism. However, it has been unsettled if variation in immune function in the general population affects the risk of fracture. We are utilizing the unique possibility to study long-term risk of osteoporosis and hip fracture across the range of immune responses assessed by the tuberculin skin test in a very large population-wide cohort. As a spinoff, we are also studying the association between immune response and osteoarthritis of the hip.
In WP3 we combine already available data on day-to-day weather conditions, climate changes, topography and air pollution with individual-level socio-demographic and fracture outcome data integrated in a Geographic Information System (GIS). This will enable us to quantify the influence of these environmental factors on fracture incidence across Norway.
The research is conducted by NOREPOS, a longstanding national research network comprising the four medical faculties in Norway and the Norwegian Institute of Public Health.
