Influence of hormonal and reproductive factors on the risk of vertebral deformity in European women. European Vertebral Osteoporosis Study Group.

The aim of this study was to determine whether variation in the level of selected hormonal and reproductive variables might explain variation in the occurrence of vertebral deformity across Europe. A population-based cross-sectional survey method was used. A total of 7530 women aged 50-79 years and over were recruited from 30 European centres. Subjects were invited to attend for an interviewer-administered questionnaire and lateral spinal radiographs which were taken according to a standard protocol. After adjusting for age, centre, body mass index and smoking, those in the highest quintile of menarche (age > or = 16 years) had an increased risk of vertebral deformity (odds ratio [OR] = 1.48; 95% confidence interval [CI] 1.16, 1.88). Increased menopausal age (> 52.5 years) was associated with a reduced risk of deformity (OR = 0.78; 95% CI 0.60, 1.00), while use of the oral contraceptive pill was also protective (OR = 0.76; 95% CI 0.58, 0.99). There was a smaller protective effect associated with one or more years use of hormone replacement therapy, though the confidence limits clearly embraced unity. There was no apparent effect of parity or breast-feeding on the risk of deformity. We conclude that oestrogen status is an important determinant of vertebral deformity. Ever use of the oral contraceptive pill was associated with a 25% reduction in risk of deformity though the effect may be a result of the higher-dosage oestrogen pills used in the past. Parity and breast-feeding do not appear to be important and would appear to have little potential for identification of women at high risk of vertebral deformity.