title: A comparison of hip fracture incidence rates among elderly in Sweden by latitude and sunlight exposure.
abstract: BACKGROUND
  Research has shown that hip fracture risk increases with latitude; hypothetically due to reduced sunlight exposure and its effect on bone quality. Sweden, with large differences in latitude and UV radiation, is ideal to study in order to analyse the association between latitude and UV radiation on age- and sex-specific hip fracture rates among elderly.
  
  
  METHODS
  Aggregated (2006-2008) age- and sex-specific hip fracture data was obtained for each Swedish municipality as well as the municipality's latitudinal coordinates and aggregated (2006-2008) UV radiation levels. Pearson correlations were calculated between hip fracture incidence rates, latitude and UV radiation. Independent t tests were calculated on tertile-categorized latitudinal data in order to investigate the difference in hip fracture risk between these categories.
  
  
  RESULTS
  Statistically significant correlations were seen in all groups between hip fracture incidence rates and latitude as well as UV radiation. The independent t tests showed that this correlation was mainly due to high incidence rates in high latitude municipalities.
  
  
  CONCLUSIONS
  Statistically significant correlations are seen between hip fracture incidence rates and latitude as well as UV radiation in Sweden and the northern parts of Sweden have an increased risk of hip fractures compared to the middle and southern parts. To our knowledge this is the first study using a national discharge register that shows this relationship and provides a starting point for further research to investigate why populations in northern Sweden have a higher risk of hip fractures compared to other Swedish regions.
authors.affiliation: Division of Risk Management, Department of Environmental and Life Sciences, Karlstad University, Karlstad, Sweden.
authors.forename: Finn
authors.initials: F
authors.lastname: Nilson
authors.forename: Syed
authors.initials: S
authors.lastname: Moniruzzaman
authors.forename: Ragnar
authors.initials: R
authors.lastname: Andersson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000531:Altitude; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D005260:Female; D006620:Hip Fractures / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008297:Male; D012042:Registries; D012307:Risk Factors; D013472:Sunlight; D013548:Sweden / Q000453:epidemiology
keywords: Elderly; UV radiation; epidemiology; falls; hip fractures; latitude