Association between the Sp1-binding-site polymorphism in the collagen type I alpha 1 (COLIA1) gene and bone phenotypes: the Dubbo Osteoporosis Epidemiology Study.

Introduction: Polymorphisms within the collagen 1 alpha 1 gene (COLIA1) have been shown to be associated with bone mineral density (BMD). This study aimed to test the hypothesis that COLIA1 polymorphisms are associated with bone loss and fragility fractures.

Materials and methods: The study involved 809 postmenopausal women aged 60 years and above in the Dubbo Osteoporosis Epidemiology Study who had COLIA1 genotypes and at least two BMD measurements over a 30-year period. BMD at the lumbar spine (LSBMD) and femoral neck (FNBMD) was measured biennially by dual-energy X-ray absorptiometry (GE-Lunar Prodigy). Fragility fracture has been ascertained by X-ray reports between 1990 and 2020. The G-> T polymorphism at the Sp1-binding site in the COLIA1 gene (rs1800012) was determined by the PCR-based method, and coded as GG, GT, and TT.

Results: Women homozygous for the minor allele (TT) tended to have greater bone loss (-0.72%/year) than those with GT (-0.58%/year) or GG (-0.56%/year) though the difference did not achieve statistical significance (P = 0.84). Women of the TT genotype were associated with a two-fold greater risk of any fracture (adjusted hazard ratio: 2.21; 95%CI 1.42-3.46) and almost fourfold greater risk of hip fracture (3.78; 1.83-7.82) than those with either GG or GT genotype.

Conclusions: Polymorphisms at the Sp1 site in the COLIA1 gene are associated with fracture risk, independent of bone loss.