Epidemiology of hip fractures in Oslo, Norway.

The incidence of hip fractures in Oslo has shown a secular increase during the past decades. The main aims of the present study were to report the current incidence of hip fractures in Oslo and to determine whether there is a seasonal variation in the occurrence of fractures. Using the electronic diagnosis registers and the lists of the operating theater for the hospitals in Oslo with somatic care, all patients with ICD-9 code 820.X (hip fracture) from May 1, 1996 to April 30, 1997 were identified. Medical records for all identified patients were obtained and diagnosis was verified. Using the population of Oslo on January 1, 1997 as the population at risk, the age- and gender-specific annual incidence rates were calculated. These rates were compared with those for 1988/89 and 1978/79. Outdoor temperature data for Oslo were obtained to study the relation between temperature and number of hip fractures. A total number of 1316 hip fractures was included, of which 78% occurred in women. An exponential increase in incidence with age was observed in both genders. The age-adjusted fracture rates per 10,000 for the age group > or =50 years were 118.0 and 44.0 in 1996/97, 124.3 and 44.9 in 1988/89, and 104.5 and 35.8 in 1978/79 for women and men, respectively. There was no significant seasonal variation in the incidence of hip fractures and no correlation between mean outdoor temperature and number of fractures for each month in 1996/97. The data show that the incidence of hip fractures in Oslo has not changed significantly during the last decade, and it is still the highest reported. The cold climate of Oslo does not seem to contribute to the high incidence.