Determinants of incidence of osteoporotic fractures in the female Spanish population older than 50

It is well known that the adoption of preventive measures for osteoporosis may contribute to minimizing its impact as a result of bone fractures. However, there are well-recognized risk factors involved in the onset of osteoporosis that are not possible to modify. Better knowledge of these non-modifiable factors could aid prevention in subjects at high risk of fractures. The aim of this study was to evaluate the likely association between gynecological, reproductive and family history of hip fracture with the incidence of vertebral and nonvertebral osteoporotic fractures in women older than 50. We studied 255 women aged 50 and over, randomly selected from a Spanish population that had participated in a study of prevalence of vertebral fractures (EVOS study). This cohort was prospectively followed for 8 years by means of four postal questionnaires, in order to find out the incidence of nonvertebral fractures. Concerning the incidence of vertebral fractures, participants were invited to repeat the lumbar spine X-rays 4 years after the initial study. A total of 31 women had incident osteoporotic fractures. The analysis of gynecological variables showed that an increase in the age at menarche was a risk factor for all incident osteoporotic fractures [OR=1.57 (1.04-2.37)]. The presence of amenorrhea at any age during the fertile period was associated with higher incidence of all osteoporotic fractures [OR=6.30 (1.61-24.70)]. Among all the reproductive variables analyzed (pregnancy, number of live births and breast-feeding) only pregnancy was an important protective factor in preventing incident Colles fracture [OR=0.15 (0.03-0.62)]. A family history of hip fracture was associated with a higher incidence of all osteoporotic fractures [OR=3.59 (1.01-12.79)]. In summary, a late age at menarche, the presence of amenorrhea and having close relatives with hip fracture were all risk factors which, independently of bone mineral density (BMD) and age, were associated with higher incidence of all osteoporotic fractures. Pregnancy was an important protective factor for the incidence of Colles fractures.