NEWS - Weight influences BMD but doesn't explain all ethnic differences in fracture risk

[Guest guest]

Weight influences BMD but doesn't explain all ethnic differences in fracture

risk

Rheumawire

Feb 10, 2005

Janis

La Jolla, CA - Analysis of osteoporosis prevalence, bone-mineral density

(BMD), and fracture risk in a cohort of nearly 200 000 women identified

interesting differences in the relationship between weight, BMD, and

fracture risk among ethnic groups [1]. For instance, the study, which was

reported in the February 2005 issue of the Journal of Bone and Mineral

Research, found that BMD was highest in black women and lowest in Asian

women and that 4.2% of black women as opposed to 10% of Asian women had

osteoporosis, but that both groups had similarly low risks of fractures.

However, lead author Dr Barrett-Connor tells rheumawire that

regardless of other differences, BMD strongly influenced fracture risk in

each ethnic group and that each standard deviation (SD) decrease in BMD

predicted a 1.54 increase in fracture risk.

Barrett-Connor says that the differences in absolute risks vs BMD are

important to remember when making treatment decisions. She writes, " The

prevalence of low BMD and the absolute risk of fracture at any given BMD do

differ among ethnic groups. . . . Further follow-up is necessary to

determine whether differences in absolute risks are large enough to warrant

ethnic-specific screening and treatment recommendations. "

The objective of the study was to describe the frequency of low BMD and the

relation between low BMD and 1-year fracture incidence among women in 5

ethnic groups: white, black, Asian, Hispanic, and Native American. The data

were pulled from the National Osteoporosis Risk Assessment observational

study of postmenopausal women. Each study participant had BMD measured at

the heel, forearm, or finger. Low BMD was defined as osteopenia

(measurements between 1 and 2.5 SD below the average for the young-normal

reference population) or osteoporosis (more than 2.5 SD below the

young-adult mean). Fracture rates were monitored over 1 year of follow-up.

The analysis included 179 470 white, 7784 black, 1912 Asian, 6973 Asian, and

1708 Native American women.

Compared with white women, the odds of osteoporosis were 0.55 for black

women, 0.96 for Native American women, 1.20 for Hispanic women, and 1.05 for

Asian women.

The analysis showed that:

At every age, BMD was highest in black women and lowest in Asian

women.

Osteoporosis was found in 11.9% of Native Americans, 10% of Asians,

9.8% of Hispanics, 7.2% of whites, and 4.2% of blacks.

Fracture rates in all ethnic groups were lowest for women with normal

BMD and highest in women with osteoporosis.

BMD generally increased with weight, but black women's BMD differences

were not entirely explained by adjusting for weight.

For all groups, fracture risk increased by 54% for each SD decline in

T score.

Despite the divergence in BMD levels between blacks and Asians, these

groups had similarly low risk of fractures.

The study included researchers from the University of California, San Diego

(La Jolla); Columbia University (New York), the University of land

(Baltimore), the Colorado Center for Bone Research (Lakewood), and Merck &

Co Inc (West Point, PA). The National Osteoporosis Risk Assessment was

funded by Merck Inc.

Dr Reina Armamento-Villareal (Washington University School of

Medicine, Seattle) reports that about 19% of the general US population has a

genetic variation linked to increased risk of osteoporosis [2]. In the same

issue of the Journal of Bone and Mineral Research, Armamento-Villareal

describes a variant of the CYB1A1 gene that speeds up the breakdown of

estrogen and is associated with low density in the bones of the hip.

" The data suggest that this particular variation of the gene

produces an enzyme that breaks down estrogen faster than usual, leading to

low serum estrogen levels and high levels of estrogen metabolites, "

Armamento-Villareal says. " Low levels of estrogen put women at risk for

osteoporosis, and our data showed a strong correlation between the genetic

variant and low bone density. "

The CYP1A1 variant might be a useful marker for evaluating

osteoporosis risk in young patients, the report suggests.

Sources

Barrett-Connor E, Siris ES, Wehren LE, et al. Osteoporosis

and fracture risk of women of different ethnic groups. Journal of Bone and

Mineral Research 2005; 20:185-194.

Napoli N, Villareal DT, Mumm S, et al. The effect of

CYP1A1 gene polymorphisms on estrogen metabolism and bone density. Journal

of Bone and Mineral Research 2005; 20:232-239.

I'll tell you where to go!

Mayo Clinic in Rochester

http://www.mayoclinic.org/rochester

s Hopkins Medicine

http://www.hopkinsmedicine.org