Bone mineral density of the lumbar spine in menopause

الملخص EN

Objective: To study the changes of the pattern of bone mineral density in Egyptian women's lumbar spine during the perimenopausal period.

Also to identify the rate of BMD loss before and after menopause as a guide to prophylaxis against postmenopausal osteoporosis.

Materials & Methods: The study was conducted on 860 healthy Egyptian women aged 45-55 years.

They were allocated in 3 major groups: Group I: Non-menopausal (n = 350), Group II: menopausal for less than 5 years (n = 294) and Group III: menopausal for more than 5 years (n = 216).

AP spine BMD was measured using dual energy x-ray absorptiometry with a Lunar DPXIQ bone densitometer.

Results: Group I were younger, lighter in weight than the other two groups.

The values of AP spine BMD, BMC and AP spine BMD % (of age and weight matched reference population) of Group I were significantly higher than values in other groups.

Likewise, the same values in Group III were significantly lower than the corresponding values in Group II.

The prevalence of osteopenia and osteoporosis in Group I (24% and 5.8% respectively) was lower than the prevalence in Group II (31.2% and 10.6% respectively).

Both groups had lower prevalence rates than Group III (35.7% and 19.3% respectively).

GI showed slight reduction in AP spine BMD as the age advanced from 45 years to 55 years (AP spine BMD = 1.18 -0.0036 x (age - 45)).

Group II showed a rapid decline in the AP spine BMD years (AP spine BMD = 1.16 - 0.01 x (age - 45)).

The curve in Group III started in a much lower AP spine BMD with a slight reduction as the age advanced from 44 years to 45 years (AP spine BMD = 1.06 -0.049 x (age - 45), R2 = 0.43).

In Group II AP spine BMD = 1.16 - (0.0225 x years after menopause).

Meanwhile, in Group III: AP spine BMD = 1.049- (.0064 x years after menopause - 5).

So, the rate of BMD drop averaged 2% per each year during the first five years after menopause and 0.06% per year in the next 5 years.

Conclusion: We suggest a dynamic normal BMD curve for the lumbar spine, which can be adjusted to the actual age of menopause so as to start the first phase of drop in L2-L4 BMD with the actual age of menopause instead of starting it at the age of 45 in all cases.

Application of this modification, allows the age of menopause to be considered in calculating the Z- score, which became the number of standard deviations away from the mean BMD of age, weight, ethnic and menopausal state matched females.