Risk factors of osteoporosis in women over 50 years of age: a population based study in the north of Iran

Objective: The objective of this study was to identify the reproductive risk factors of osteoporosis in women over the age of 50 years in north of Iran. Extensive differences in the epidemiological pattern of osteoporosis on the basis of geographical and ethnic grouping have been reported. Previous studies addressing these issues in Iran are very limited. Materials and Methods: This survey is a population-based study of the women over 50 years of age in the north of Iran in 2004. All recruited subjects were interviewed by purpose-trained interviewers using structured questionnaires including demographic variables, reproductive and medication history. Diagnosis of osteoporosis was based on ultrasonography and the positive cases were confirmed by dual X-ray absorptiometry (DEXA). Statistical analyses were performed using χ2 test, t-test, and analysis of variance. The adjusted odds ratio and 95% confidence intervals (CI) were reported by multiple logistic regression analyses. Results: Of the 796 women who participated in this study, 147 women (18.5%) were identified as having osteoporosis. Significant correlations were found between osteoporosis and parameters of age, age at menarche, parity, years of menstruation, educational level, job, physical activity, exercise, body mass index (BMI), usage of oral contraceptive pills and menopausal status. After adjusting for variables, the age of 70 years or more and the passage of more than 15 years since menopause were identified as significant risk factors for osteoporosis (OR=2.76 and 1.83, respectively). In comparison to being a ‘housewife’, having a job and physical activity of more than 3 hours a week and a body mass index (BMI) of more than 25 were identified as protectors against osteoporosis. Discussion: In spite of the low incidence of smoking and alcohol intake in our population as risk factors of osteoporosis, the prevalence of this worldwide public health problem is high in the north of Iran. These findings should help to identify women at risk and to design an early strategy based on eliminating modifiable risks for prevention of osteoporosis.