New Study 'Changes Understanding of Bone Loss After Menopause'

Marlene Busko

November 03, 2021

In the longest study of bone loss in postmenopausal women to date, on average, bone mineral density (BMD) at the femoral neck (the most common location for a hip fracture) had dropped by 10% in 25 years — less than expected based on shorter studies.

Specifically, average BMD loss at the femoral neck was 0.4% per year during 25 years in this new study from Finland, compared with a drop of 1.6% per year over 15 years reported in other cohorts.

Five-year BMD change appeared to predict long-term bone loss. However, certain women had faster bone loss indicating that they should be followed more closely.

"Although the average bone loss was 10.1%...there is a significant variation in the bone loss rate" among women in the study, senior author Joonas Sirola, MD, PhD, associate professor, University of Eastern Finland, and coauthor Heikki Kröger, MD, PhD, a professor at the same university, explained to Medscape Medical News in an email, so "women with fast bone loss should receive special attention.

The findings from the Kuopio Osteoporosis Risk Factor and Prevention (OSTPRE) study by Anna Moilanen and colleagues were published online October 19 in the Journal of Bone and Mineral Research.

Several factors might explain the lower than expected drop in femoral neck BMD (the site that is used to diagnose osteoporosis), Sirola and Kröger said. BMD depends on a person's age, race, sex, and genes. And compared with other countries, people in Finland consume more dairy products, and more postmenopausal women there take hormone replacement therapy (HRT).

"If otherwise indicated, HRT seemed to effectively protect from bone loss," the researchers noted.

Also, the number of women who smoked or used corticosteroids was low, so bone loss in other populations may be higher. Moreover, the women who completed the study may have been healthier to start with, so the results should be interpreted with caution, they urge.

Nevertheless, the study sheds light on long-term changes in BMD in postmenopausal women and "stresses the importance of high peak bone mass before menopause and keeping a healthy weight" during aging to protect bone health, they say.

Indeed the work, "changes our understanding of bone loss in older women," said Kröger in a press release from the university.

Check BMD Every 5 Years After Menopause

Invited to comment, American Society of Bone and Mineral Research (ASBMR) President Peter R. Ebeling, MD, who was not involved with the research, noted key findings are that the rate of femoral neck bone loss after perimenopause was far less than previously expected, and 5-year BMD change appeared to predict long-term bone loss in postmenopausal women.

"We know bone loss begins 1 year before menopause and accelerates over the next 5 years, " Ebeling, from Monash University, in Melbourne, Victoria, Australia, added in an email. "This study indicates some stabilization of bone loss thereafter with lesser effects of low estrogen levels on bone."

"It probably means bone density does not need to be measured as frequently following the menopause transition and could be every 5 years, rather than every 2 years if there was concern about continuing bone loss."

Baseline Risk Factors and Long-Term Changes in BMD

For the study, researchers examined the association between risk factors for bone loss and long-term changes in femoral neck BMD in 2695 women living in Kuopio who were 47 to 56 years old in 1989. The women were a mean age of 53 years and 62% were postmenopausal.

They answered questionnaires and had femoral neck BMD measured by DEXA every 5 years.

A total of 2695, 2583, 2482, 2135, 1305, and 686 women were assessed at baseline and 5-, 10-, 15-, 20- and 25-year follow-ups, respectively, indicating significant study drop-out by 25 years. 

By then, 17% of patients had died, 9% needed long-term care, some were unwilling to continue in the study, and others had factors that would have resulted in DEXA measurement errors (eg, hip implants, spine degeneration).

Researchers divided participants into quartiles of mean initial femoral neck BMD: 1.09 g/cm2, 0.97 g/cm2, 0.89 g/cm2, and 0.79 g/cm2, corresponding with quartiles 1 to 4 respectively (where quartile 1 had the highest initial femoral BMD and quartile 4 the lowest).

At 25 years, the mean femoral BMD had dropped to 0.97 g/cm2, 0.87 g/cm2, 0.80 g/cm2, and 0.73 g/cm2 in these respective quartiles.

Women lost 0.9%, 0.5%, 3.0%, and 1.0% of their initial BMD each year in quartiles 1 to 4, respectively.

And at 25 years, the women had lost 22.5%, 12.5%, 7.5%, and 2.5% of their initial BMD in the four quartiles, respectively.

Women in quartile 1 had the greatest drop in femoral BMD at 25 years, although their mean BMD at 25 years was higher than the mean initial BMD of the other women. 

The prevalence of bone-affecting diseases, smoking, and use of vitamin D/calcium supplementation, corticosteroids, or alcohol was similar in the four quartiles and was not associated with significant differences in annual bone loss.

The Most Important Protective Factor Was HRT

However, body mass index (BMI) and HRT were significantly different in the four quartiles.

On average, women in quartile 1 had a mean BMI of 26.7 kg/m2 at baseline and 27.8 kg/m2 at 25 years. Women in quartile 4 (lowest initial BMD and lowest drop in BMD) had a mean BMI of 24.9 kg/m2 at baseline and 28.4 kg/m2 at 25 years.

Women in quartile 4 (lowest initial BMD and lowest drop in BMD) were more likely to take HRT than women in quartile 1 (highest initial BMD and highest drop in BMD), at 41% vs 26%, respectively.

"The average decrease in bone mineral density was lower than has been assumed on the basis of earlier, shorter follow-ups where the bone loss rate at the femoral neck has been estimated to be even more than 20%," Sirola commented in the press release.

"There were also surprisingly few risk factors affecting bone mineral density. The most significant factor protecting against bone loss was hormone replacement therapy. Weight gain during the follow-up also protected against bone loss," Sirola added.

The study was funded by the Academy of Finland, Finnish Ministry of Education and Culture, and the Päivikki and Sakari Sohlberg Foundation. The authors and Ebeling have reported no relevant financial relationships.

J Bone Miner Res. Published online October 19, 2021. Full Text

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