Relationship between soft tissue body composition and bone mass in perimenopausal women
Introduction
Perimenopause, the transition into menopause, marks the beginning of accelerated bone loss [1], [2], contributing to the development of osteoporosis, a major public health problem. The rate of spinal bone loss during this transition (−1.83% per year) exceeds that of women in the early menopausal period (−1.29% per year) [1]. This perimenopausal transition has also been associated with a decrease in body lean mass, an increase in fat mass, and an increase in body weight [3]. It is currently unknown how the changes in fat mass and lean mass during perimenopause influence bone mass, expressed as bone mineral density (BMD). Thus, research regarding the relationship between soft tissue body composition (lean mass and fat mass components) and BMD during perimenopause could potentially contribute to the primary prevention of osteoporosis by identifying factors that are important in maintaining bone mass. The purpose of this study was to determine the independent effect and relative contribution of lean and fat mass to BMD in perimenopausal women.
Section snippets
Background
Perimenopause has been recognized as a separate entity in the menopausal process [4]. It begins a few years before actual menopause when women experience changes in menstrual pattern including menstrual cycle irregularity, change in menstrual flow, and ending with no menstruation for 12 months. These changes are secondary to diminished ovarian function. Since circulating estrogen from extraglandular aromatization is important in preventing bone loss in women with menstrual irregularity and
Subjects
This report represents baseline data from a longitudinal study investigating the effect of exercise, alone and in combination with HRT on perimenopause-associated symptoms, body composition and BMD in perimenopausal women using a randomized block-controlled trial with repeated measures pre- and post-intervention. The study protocol was approved by the Institutional Review Board of our University Medical Center. In total, 43 sedentary perimenopausal women aged 40–55 (mean=49.6; S.D.=±3.2) with (n
Results
Table 1 shows the subjects' characteristics. The average age of participants was 49.6 years with a range in BMI of 22–42. White women were predominant in the study compared to the Black/Hispanic women (83.7%, n=36; 16.3%, n=7, respectively). Because serum E2 levels were skewed, log E2 was used in the analyses.
Table 2 shows the results of total and regional BMD and body composition. Six women (14%) were identified as having low bone mass (S.D.<−1.0, but >−2.5), three lumbar, two femoral, and one
Discussion
In this study, we examined the relationship between soft tissue body composition and BMD in women in transition into menopause, a major strength. In these women, we found that lean mass positively influences femoral BMD. This is in agreement with others [6], [9], who found that lean mass, rather than fat mass, was the principal determinant of BMD. The positive association between lean mass and femoral BMD may reflect a genetic association between higher peak BMD and higher lean mass or a
Summary
In summary, our results show that lean mass rather than fat mass is a significant determinant of femoral BMD in perimenopausal women, suggesting that the endocrine effect of fat mass on BMD remains minimal or confounded by the dominant effect of ovarian estrogen during perimenopause. As lean mass is more genetically related to bone mass, whether an increase in lean mass would lead to better bone is still unknown. Longitudinal studies are necessary to examine the relationship between changes in
Acknowledgements
This work was supported by a grant from NIH: ORWH/NINR R55 NR04946.
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