Associations of the collagen type Iα1 Sp1 polymorphism with five-year rates of bone loss in older adults

The collagen type [alpha 1 Spl (ColIA1) polymorphism has been associated with reduced bone mineral density (BMD) and increased prevalence of osteoporosis. This study examines associations of the ColIA1 genotype with BMD and 5-year rates of change in BMD in elderly men and women. The 243 subjects, aged 65 years and older, were participants in two consecutive studies lasting a total of 5-years. BMD of the total body, femoral neck, and lumbar spine were made by dual-energy X-ray absorptiometry (DXA), The distribution of the genotypes (155 in the SS genotype, 79 in Ss, and 9 in ss) was proportionately similar to those reported by others. Baseline BMD did not differ significantly at any skeletal site. Unadjusted 5-year percent changes in BMD differed significantly by genotype only at the total body (P = 0.009), where the change was -0.29 +/- 0.21 (SEM) in the SS genotype, -0.60 +/- 0.25 in the Ss genotype, and -3.01 +/- 0.72 in the ss genotype. This 9.4% increase in bone loss of the ss genotype relative to the SS genotype was reduced to an 8.9% increase after adjustment for sex, age, weight, and supplementation group. Results at the femoral neck were directionally similar, but not statistically significant. No effect of genotype on change in spine BMD was observed. In conclusion, bone loss from the total body was significantly greater in elderly men and women who were homozygous for the s allele compared with heterozygotes and SS homozygotes. This finding suggests a possible explanation for the association of the ColIA1 polymorphism with increased rates of osteoporotic fracture, but should be interpreted with caution because of the small number of subjects in the unfavorable ss genotype. has been associated with deficits in BMD of premenopausal women [2] and other postmenopausal women [3, 4], though others did not observe similar associations [5, 6]. Additional investigators have reported that adults in the unfavorable ss and/or Ss genotypes are at increased risk of osteoporotic fracture compared with those in the SS genotype [3, 6]. In the largest study to examine ColIA1 genotypes, Uitterlinden et al. [3] reported a significant interaction of the genotype effect with age, such that genotype-related differences in femoral neck BMD were more pronounced in women over age 70 than in younger women. This suggests that, in addition to any effects it may have on peak bone density, the genotype may be associated with increased rates of bone loss in old age. The pul pose of the present study was to examine associations of the ColIA1 genotype with BMD and 5-year rates of change in BMD in men and women age 65 or older at the time of their baseline measurements.