The problem of increasing risk to bone fractures may be due to genetical reasons, said a study in the September issue of Archives of Internal Medicine.
Bone fractures resulting from osteoporosis have a profound impact on quality of life , with only one third of patients regaining their pre-fracture level of function and a substantial risk of death following fracture, according to background information in the article. The authors suggest that twin studies provide one of the most natural study populations for evaluating genetic risk (the relative contribution of genes versus environment). If heritable factors contribute to fractures, monozygotic twins (who have all the same genes, commonly called identical twins) are more likely to have similar rates of fracture than dizygotic twins (who share about half the same genes, commonly called fraternal twins).
Researchers from the Uppsala University Hospital, Uppsala, Sweden, had used the Swedish Twin Registry, the Swedish Inpatient Registry and telephone interviews to evaluate the genetic liability to fracture of the elderly. From the registry of Swedish twins born between 1,896 and 1,944 (3,724 identical twins, 6,314 fraternal same-sex twins and 5,736 fraternal different-sex twins), the researchers were able to identify 6,021 twins with any fracture, with a higher proportion among women (23 percent) than men (14 percent). More than half the cases (3,599) were classified as osteoporotic fractures. The most important osteoporotic fracture, hip fracture, was recorded for 1,055 twins.
Genetic variation in liability to fracture differed considerably by type of fracture and age, the authors report. Less than 20 percent of the overall age-adjusted fracture variance was explained by genetic variation. Heritability was considerably greater for first hip fracture before the age of 69 years and between 69 and 79 years than for hip fractures after 79 years of age.