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To find defects in genes that cause diseases, geneticists test whether a change or variation in a gene is associated with a disease or an increased susceptibility. Morrison first reported in 1994 that a slight variation in the vitamin D receptor gene (VDRGP) is associated with a significant change in our bone mineral density (BMD). By January of 1997, seventy-five independent investigations had been published, and no consensus had been reached as to whether BMD is really associated with VDRGP. We analyzed all the 75 publications using a fuzzy mathematics approach to address this issue. We use two methods, one based on preference relations, and the other based on p-values. Fifty-five studies on spinal BMD and 73 on hip BMD were analyzed. Results from method I found that VDRGP affects spinal BMD strongly among pre-menopausal populations, and moderately among post-menopausal populations, and populations with pre- and post-menopausal women combined. No relations were found in populations with males and females combined. VDRGP was associated with hip BMD among pre-menopausal, but not any other, populations. Using method II we found that VDRGP was associated with spinal BMD only in pre-menopausal women, and VDRGP was somewhat associated with hip BMD in all four types of populations. Conclusion: BMD is associated with VDRGP in certain populations, but not in others. Heterogeneity of populations studied seems to be responsible for the discrepancies among studies. |
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