Regional differences in hip bone mineral density levels in Norway: the NOREPOS study

Summary

Large regional differences in hip fracture rates within Norway have previously been shown. However, regional differences in hip bone mineral density (BMD) have not yet been assessed. In this study including 10,504 hip scans, there were significant regional differences in BMD. Further studies to address reasons for the regional differences in hip fracture risk are warranted.

Introduction

Bone mineral density (BMD) at the hip is an important determinant of hip fracture. While regional differences in Norwegian hip fracture rates have previously been shown, no comparative studies of hip BMD have been conducted.

Methods

Total hip BMD was measured by DXA in two population-based studies across Norway during 1997–2002. Valid hip scans with in vivo calibration were obtained from 5127 subjects in Tromsø (age 30–89 years) and 5377 subjects in Bergen (age 47–50 and 71–75 years).

Results

Women ≥60 years in Tromsø had 0.052 g/cm² higher age-adjusted BMD than women in Bergen, whereas BMD among women <60 years was similar in Tromsø and Bergen. Age-adjusted total hip BMD was 0.035 g/cm² lower in men ≥60 years in Bergen compared with Tromsø, and the corresponding figure for men <60 years was 0.028 g/cm². While adjustment for body mass index explained some, but not all of the differences, smoking, physical activity, diabetes prevalence, self-perceived health, intake of alcohol and estrogen use did not.

Conclusions

Regional differences in BMD at the hip were found in Norway. Reasons for this and potential impact on hip fracture rates should be explored in further studies.