Association of the collagen type 1 (COL1A 1) Sp1 binding site polymorphism to femoral neck bone mineral density and wrist fracture in 1044 elderly Swedish women

Identification of risk factors for osteoporosis has been essential for understanding the development of osteoporosis and related fragility fractures. A polymorphism of the binding site for the transcription factor Sp1 of the collagen I alpha 1 gene (COLIA1) has shown an association to bone mass and fracture, but the findings have not been consistent, which may be related to population differences. The Sp1 polymorphism was determined in 1044 women, all 75 years old, participating in the population-based Osteoporosis Prospective Risk Assessment study in Malmo (OPRA). Bone mineral density, heel ultrasound and all previous fractures were registered. BMD was 2.7% lower in the femoral neck in women carrying at least one copy of the "s" allele (P = 0.027). There was no difference in bone mass at any other site, weight, BMI or age at menopause. Women with a prevalent wrist fracture (n = 181) had an increased presence of the "s" allele. The odds ratio for prevalent wrist fracture was 2.73 (95% CI 1.1-6.8) for the ss homozygotes and 1.4 (95% Cl 1.0-2.0) for the Ss heterozygotes when compared with the SS homozygotes. In conclusion, in this large and homogenous cohort of 75-year-old Swedish women, there was an association among the Sp1 COLIA1 polymorphism, bone mass, and fracture. The presence of at least one copy of the "s" allele was associated with lower femoral neck BMD and previous wrist fracture and in addition, it was related to an increased risk for wrist fracture.