Moreover, it is not clear how much of the etiology of osteoporosis can be explained by allelic variation in these genes and in yet to be discovered genes. Finally, it is not clear how these and other genes interact with the traditional risk factors for osteoporosis such as calcium and smoking. Assessing gene-environment interaction in chronic diseases will become an important public health research priority in the post Human Genome Project era. The nature vs. nurture controversy is being replaced by systematic evaluation of nature-nurture interaction. As more genes and their numerous allelic variants are discovered, it becomes crucial to assess how modifiable risk factors such as diet or drugs interact with genetic risk factors to influence disease risks.
Methods used in genetics and epidemiology to study gene-environment interaction continue to evolve.
The purpose of such studies is to provide clues to the importance of genetic factors embodied in the concept of heritability and measured by analysis of variance or correlation. Neither environmental exposures nor specific genes are measured at this stage. These and other approaches are emerging as ways of combining the methodologic strengths of the fields of genetics and epidemiology. In the final analysis, however, once specific genes are found using any number of techniques, and once allelic variations that lead to altered gene products are identified, it could become relatively simple to integrate such findings into traditional epidemiologic designs. While the usefulness of heritability studies will diminish, population-based epidemiologic studies will increasingly use genotype measurements at specific loci in addition to traditional risk factor information to identify interactions and refine risk estimates associated with infectious, chemical, or nutritional factors according to genetic susceptibility.