Associations of the collagen type I alpha 1 Sp1 polymorphism with five-year rates of bone loss in older adults

The collagen type [alpha 1 Spl (ColIA1) polymorphism has been associated wi th reduced bone mineral density (BMD) and increased prevalence of osteoporo sis. 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, ag ed 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 th e genotypes (155 in the SS genotype, 79 in Ss, and 9 in ss) was proportiona tely similar to those reported by others. Baseline BMD did not differ signi ficantly at any skeletal site. Unadjusted 5-year percent changes in BMD dif fered significantly by genotype only at the total body (P = 0.009), where t he change was -0.29 +/- 0.21 (SEM) in the SS genotype, -0.60 +/- 0.25 in th e 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 g roup. Results at the femoral neck were directionally similar, but not stati stically significant. No effect of genotype on change in spine BMD was obse rved. In conclusion, bone loss from the total body was significantly greate r in elderly men and women who were homozygous for the s allele compared wi th heterozygotes and SS homozygotes. This finding suggests a possible expla nation 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 asso ciated with deficits in BMD of premenopausal women [2] and other postmenopa usal 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 compare d with those in the SS genotype [3, 6]. In the largest study to examine Col IA1 genotypes, Uitterlinden et al. [3] reported a significant interaction o f the genotype effect with age, such that genotype-related differences in f emoral neck BMD were more pronounced in women over age 70 than in younger w omen. This suggests that, in addition to any effects it may have on peak bo ne density, the genotype may be associated with increased rates of bone los s 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 a nd women age 65 or older at the time of their baseline measurements.