Risk factors for osteoporosis
Maturitas 2008;in press
A postmenopausal woman’s risk of osteoporosis appears to be related more to the duration of menopause at the time of measuring bone mineral density than to the age at menopause, according to new findings from a large study.
In a paper due to be published in the journal Maturitas, specialists (Demir et al) from the Ministry of Health Ankara Etlik Maternity and Women’s Health Teaching Research Hospital and from Hacettepe University, Turkey, present their study of the records of 2,769 postmenopausal women who had attended a menopause outpatient clinic at the teaching hospital and who had not taken any hormone replacement therapy or anti-osteoporosis treatment.
The aim of the study was to determine the effect of different durations of menopause and of different age at menopause on the prevalence of osteoporosis and osteopenia as defined by World Health Organization criteria.
Overall, the mean age of the women was 52.9 years (range 40-63 years), with a mean menopause duration of 4.5 years and median parity of three. Dual-energy X-ray absorptiometry (DXA) scan results indicated that 16.2 percent of the women had osteoporosis, 39.2 percent had osteopenia, and the remaining 44.6 percent had normal bone mineral density.
For the analyses, the researchers first divided the women into three groups according to the duration of menopause at the time of measuring bone mineral density: 0-3 years, 4-7 years and more than 7 years.
They found a statistically significant association between the duration of menopause and the prevalence of osteoporosis. The prevalence increased from 10.6 percent in women with a duration of 0-3 years, to 16.2 percent in women with a duration of 407 years, to 31.9 percent in women with a duration of more than 7 years.
There was no such association between duration and osteopenia, the prevalence of which remained relatively stable: 37.2 percent, 42.1 percent, and 40.9 percent, respectively.
The researchers also divided the women in the study into four different groups according to age at menopause onset. A total of 30 percent of women aged younger than 40 years at menopause had osteoporosis. The prevalences in the other three groups were similar, at 18.3 percent in women aged 40-46 years, 14.1 percent in women aged 47-52 years, and 15.4 percent in women aged more than 52 years at menopause onset. For osteopenia, the corresponding prevalences were 36.7 percent, 40 percent, 39.1 percent and 39 percent.
The researchers conducted logistic regression analyses and found that duration of menopause at the time of bone mineral density measurement and parity were both positively correlated with both osteoporosis and osteopenia. Age at menopause was negatively correlated with osteoporosis only. Age at menopause contributed just 0.8 percent to the overall regression model, while menopause duration contributed 5.6 percent.
In addition, the researchers observed a small but significant negative association of fasting blood glucose with osteoporosis and osteopenia. There was also a small but significant association between LDL-cholesterol level and the risk of osteopenia.
Discussing their findings, the researchers note that women with more than 7 postmenopausal years at the time of bone mineral density testing and women with an age at menopause onset younger than 40 years had the highest risk of osteoporosis.
They conclude: “According to our results, osteoporosis is related more to the duration of menopause at the time of bone mineral density measurement rather than the menopause onset age among untreated postmenopausal women. Furthermore, high parity was determined to be another risk factor of low bone mineral density