Introduction: Epidemiological observations suggest that sunlight exposure is an important determinant of hip fracture risk. The aim of this ecological study was to examine the relationship between latitude and hip fracture probability.
Methods: Hip fracture incidence and mortality were obtained from literature searches and 10-year hip fracture probability computed from fracture and death hazards.
Results: There was a significant association between latitude and 10-year hip fracture probability. For each 10 degrees change in latitude from the equator (e.g., from Paris to Stockholm), fracture probability increased by 0.3% in men, by 0.8% in women and by 0.6% in men and women combined. There was also a significant association between economic prosperity and hip fracture risk as judged by gross domestic product (GDP)/capita or the use of mobile phones/capita. A US $10,000 higher GDP/capita was associated with a 1.3% increase in hip fracture probability. The association between latitude and hip fracture probability persisted after adjusting for indices of economic prosperity.
Conclusions: These findings provide support for an important role of sunlight exposure in the global variation of hip fracture risk. In addition, there is a need to identify the factors related to socioeconomic prosperity that may provide mechanisms for the variation in hip fracture probability worldwide.