Kemerovo State Medical Academy,

Kemerovo, Russia

Bone tissue metabolic disease, osteoporosis, takes a leading part among the infectious diseases according to the medical, social and economic consequences. According to International Osteoporosis Foundation (IOF), osteoporosis is observed in approximately 22 million women and 5.5 million men at the age of 50 and older in the European countries. There is a tendency to the constant increase in incidence of this pathology [1].

In Russian Federation about 34 million persons have high risk of osteoporotic fractures [2].

The high incidences of osteoporosis and, as result, the high frequency of fractures are accompanied by significant economic losses. The treatment of patients with osteoporosis was associated with costs of 1,486 million Euro in 2010 in Sweden. By 2025 economic burden will increase to 1,826 million Euro. In Spain the economic costs for osteoporosis were 2,842 million Euro in 2010. By 2025 the increase by 30 %, up to 3,680 million Euro, is anticipated. In Germany such costs were 9,008 million Euro in 2010, with anticipated increase by 25 % in 2025, i.e. 11,261 million Euro [1].

At the present time, radial methods take the leading part in osteoporosis diagnostics: dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT). DXA is the most common technique.

Dual-energy X-ray absorptiometry technique evaluates general two-dimensional mineral density of trabecular and cortical bones. The indices of bone mineral density are compared against reference database, which is included to a densitometer by a producing company. These reference indices vary between the regions. As the reference values, the database from National Health and Nutrition Examination Survey (NHANES) [3] is used in most devices.

It is known that osteoporosis development is significantly related to regional features (geographic location, external environmental factors, population and ethnic characteristics) [4].

The geographic localization of Kemerovo region favors accumulation of industrial emissions in Kuznetsk basin [5], with negative influence on health of the population and increasing the rates of musculoskeletal system diseases [6, 7].

Therefore, development of reference databases based on values of bone mineral density in healthy individuals of a certain region will favor more precise evaluation of results of bone densitometry in the women of Kemerovo region.

Objective – to develop reference database of two-dimensional bone mineral density indices for women of Kuzbass.

MATERIALS AND METHODS

The present study included 1,504 white women living in Kemerovo region, who received dual-energy X-ray absorptiometry.

The presented study was performed with compliance of the ethic standards of World Medical Association's Declaration of Helsinki – Ethical Principles for Medical Research Involving Human Subjects, with amendments from 2000 and the Rules for Clinical Practice in Russian Federation confirmed by the order of Health Ministry of Russian Federation from 19.06.2003, #266. All women gave written consent for dual-energy X-ray absorptiometry and preparation of received data.

The inclusion criteria were duration of living in Kuzbass at least 10 years; Caucasian race; absence of diseases resulting in osteoporosis formation; consent for bone densitometry.

The exclusion criteria were duration of living in Kemerovo region at least 10 years, smoking, presence of diseases resulting in secondary osteoporosis, administration of hormonal contraceptives, hormonal replacement therapy, administration of drugs leading to osteoporosis, absent consent for research.

Dual-energy X-ray absorptiometry was conducted with bone X-ray densitometer Lunar-DPX-NT. The regions of interest were L₁-L₄ vertebrae. Two-dimensional bone mineral density was examined. The units of measurement were g/cm².

The examined women were distributed into the age groups: 16-19 years (n = 74), 20–29 (n = 178), 30–39 (n = 244), 40–49 (n = 301), 50–59 (n = 275), 60–69 (n = 207), 70–79 (n = 123), 80 and older (n = 102).

After receiving the study results the statistical preparation of the data was performed using Microsoft Excel and Statistica 6.1. The mean (M) of bone mineral density and standard deviation (SD) for each age group were defined. Student’s test for matched samples was used for comparison of two groups. P value of 0.05 was considered as statistically significant.

According to the existing recommendations [8] it is necessary to evaluate bone mineral density of at least two lumbar vertebrae (L₁–L₂, L₁–L₃, L₁–L₄, L₂–L₃, L₂–L₄, L₃–L₄). However, in actual practice it is commonly to use only BMD indices of L₂-L₄ and L₁-L₄.

Besides calculation of mean values of bone mineral density for bone densitometer Lunar, the standardization of values for Hologic and Norland densitometric systems was performed.

The standardization of BMD values was performed on the basis of the following formulae [9, 10]:

For Lunar bone densitometer:

Standardized BMD = 0.9683 × (BMD_Lunar−1.100) + 1.0436.

For Hologic bone densitometer:

Standardized BMD = 1.0550 × (BMD_Hologic−0.972) + 1.0436.

For Norland bone densitometer:  

Standardized BMD = 0.9743 × (BMD_Norland−0.969) + 1.0436.

RESULTS AND DISCUSSION            

The tables 1, 2, 3 include the reference values of bone mineral density of vertebrae in women of Kemerovo region (after examination with different densitometric systems – Lunar, Hologic, Norland). The tables show that peak values of bone mass in the women of Kemerovo region is related to age of 20-30. After that BMD plateau is observed. The statistically significant decrease in BMD values for lumbar vertebrae is noted in the age group of 40-49.

Table 1 The reference values of bone mineral density in lumbar vertebrae in women of Kemerovo region (bone densitometer Lunar DXA Systems)

Table 2
The reference values of bone mineral density in lumbar vertebrae in women of Kemerovo region (bone densitometer Lunar DXA Systems

Table 3
The reference values of bone mineral density in lumbar vertebrae in women of Kemerovo region (bone densitometer Lunar DXA Systems)

The received reference values of bone mineral density for lumbar vertebrae in women of Kemerovo region were compared against the reference values from National Health and Nutrition Examination Survey (NHANES) database (table 4).

Table 4
The comparative assessment of the reference values of BMD in lumbar vertebrae in Kuzbass women and the reference values from NHANES database

The table 4 shows that in the age groups of 16-19 and 20-29 the statistically significant differences in BMD were absent. However, because of the fact that the peak bone mass in women of Kemerovo region is observed earlier compared to USA white women, beginning from age of 30-39, the statistically significant difference of BMD mean values was found, except for age groups of 70-79. At the same time, absence of statistically significant differences in these age groups can be related to the disparity in numbers in two compared groups.

The figure shows the age dynamics of reference values of two compared groups.

Figure

The comparative age dynamics of the reference values of lumbar BMD in Kuzbass women and the reference values from NHANES database

 

CONCLUSION

The following conclusions can be made after completing the study:

1. The peak bone mass is related to the age of 20-29 in women of Kemerovo region. During the following decade bone mineral density is stable.

2. After age of 40, statistically significant decrease in BMD values in lumbar vertebrae is observed.

3. There were no statistically significant differences in L₁-L₄ BMD in the age groups of 16-19 and 20-29 after comparison of reference values in women of Kemerovo region and the data from National Health and Nutrition Examination Survey.

4. Beginning from the age of 30-39 and older BMD values in Kuzbass women were reliably lower, except for the age group of 70-79 without statistically significant differences.

Therefore, the developed reference database of lumbar vertebral bone mineral density in women of Kemerovo region will allow performing dual-energy X-ray absorptiometry with consideration of regional features. It will increase the quality of diagnostics of osteopenia and osteoporosis.