Article Text
Abstract
Background Twin and family studies have demonstrated that an important degree of the population variance in bone mineral density (BMD) is attributable to genetic factors.
Objectives A polymorphism in the collagen type I alpha 1 (COLIA1) gene has recently been associated with low bone mass and fracture incidence.
Methods We analysed the relationship between COLIA1 gene polymorphism, lumbar spine and hip BMD, T-score and fracture incidence in a population of 319 postmenopausical women classified by WHO standards: 98 non-osteoporotic women (NOPW) (57.4 ± 6.2 yrs), 146 osteoporotic women without fracture (OPW without fracture: OPWnF)(60.0 ± 5.2) and 75 osteoporotic women with fracture (OPW with fracture: OPWwF) (61.2 ± 6.3 yrs). The COLIA1 genotype was assessed by polymerase chain reaction and Bal I endonuclease digestion. Genotype frequencies for the total group were 49.2% “SS” homozygotes, 39.5% “Ss” heterozygotes and 11.3% “ss” homozygotes.
Results We found significant differences in the percentage of homozygous “ss” between NOPW and OPW (6.1% and 13.6% respectively). However, the incidence of genotype “ss” in OPWnF was 6.2% and 28% in OPWwF. We observed no associations between the COLIA1 genotype and lumbar and hip BMD. However, the lumbar spine T-scores were lower in the “ss” group than in the “Ss” and “ss” group. The incidence of fractures (64 vertebral and 11 colles) varied significantly by genotype: “SS” 21.7%; “Ss” 15.9%; and “ss” 58.3% (chi-square = 15.43; p < 0.0001); this resulted in a fracture odds ratio of 5.96 (95% confidence interval 2.26–15.69). Logistic regression analysis of fracture prevalence showed that for prevalent fractures, the women with “ss” group had 4.17 times risk of the woman “SS”+ “Ss” groups. When prevalence was adjusted for BMD and T-scores, the respective fracture risk was 2.6 and 2.94 for the “ss” group versus the other genotypes (SS+Ss).
Conclusion A slight association was found between lumbar T-score and gene COLIA1 polymorphism. Expression of the “ss” allele seems to be related with a higher incidence of fracture in postmenopausical women and was independent of bone mineral density.