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'Mandela's Paradox' may show that osteoporosis propensity starts in pre-teen years
Black South African adults have very low hip fracture rate despite low calcium intake and exercise rates as youths -
After Nelson Mandela was released from prison February 11, 1990, all children born in the greater Johannesburg area were
enrolled in a 20-year longitudinal study. Officially known as "Birth to Twenty," the study and its 3,273 youth, are
colloquially referred to as "Mandela's Children." It's the largest and longest running study of child and adolescent health
and development in Africa, and one of the few large-scale longitudinal studies in the world.
One of the main aims of the study is to follow bone health in growing children, specifically the differences in bone mass
acquisition between black and white children and the factors that influence this.
Besides its obvious importance in adult health and possibly measuring the change from "third world" population to "developed
world" population, there is a situation in South Africa that's very counterintuitive, and possibly unique: "Black South
African adults have among the lowest hip fracture rates in the world," according to the study's lead author, Joanne A.
McVeigh.
"Yet our study found that, as children, blacks have significantly lower physical activity levels and calcium intakes than
age- and gender-matched white children," McVeigh adds. McVeigh is presenting the research at the 35th Congress of the
International Union of Physiological Sciences in San Diego, March 31 - April 5, 2005.
*Paper presentation: "Physical activity and bone mass accumulation patterns differ in black and white South African
children," by Joanne A. McVeigh, Shane A. Norris and John M. Pettifor, MRC Mineral Metabolism Research Unit, Department of
Paediatrics, and School of Physiology, University of Witwatersrand Medical School, Johannesburg. 12:30 p.m.-3 p.m. Sunday
April 3, Physiology session/abstract: 347.8; board #A64. On view 7:30 a.m. - 4 p.m.
9- and 10-year-olds compared for exercise level, bone mineral content
Since it's accepted that physical activity has an osteogenic effect on bone mass, the relationship between physical activity,
or exercise, and bone mineral content (BMC) levels in black and white South African children was compared across the ages of
9 and 10 - halfway through the 20-year study.
White children's mean exercise scores didn't differ between ages 9 and 10, however black children's level significantly
increased - by about 50%. "We expected that an increased exercise level would be associated with greater BMC, especially at
the hip," McVeigh said. "However, both group's BMC gains over that year were similar at the hip."
Indeed, over the same year, white kids showed a significantly greater change in height, whole body and spine BMC. Significant
positive correlations between exercise and BMC accumulation were found for white children at the whole body, hip and spine,
but not for black children.
"Nevertheless, after controlling for body weight and bone area, black children remained with the advantage of a significantly
greater hip BMC both at ages 9 and 10," McVeigh reported. This, despite the fact the researchers found that overall white
children are much more physically active and have significantly higher calcium intakes than black children.
"However, when we compared bone mass within different quartiles of activity, we found that the most active white children did
indeed have better bone mass than the most active black children, but black children have a lower and narrower range of
physical activity. Physical activity appears to be the most important modifiable factor influencing white children's bone
health," she noted.
Paradox indicates need for re-thinking osteoporosis development
"The results of our study raise an apparent paradox, which has implications on our thinking about osteoporosis, the roots of
which may well lie in the childhood years. It's obvious that intervention is becoming increasingly important during the
growing years as this is the period when physical activity and nutrition have the most impact. It is possible that with the
black South African population starting to adopt more 'Western' lifestyles, we may see an increase in fracture rates as their
genetic advantage is outweighed by lifestyle influences. It will be important to follow up on these children and our study
will continue to do this, throughout their pubertal years and until they turn 20. Only time will tell if these trends will
persist."
Funding: Research was funded by the Medical Research Council (South Africa) and the Wellcome Trust (U.K.).
The 35th Congress of the International Union of Physiological Sciences is in San Diego, March 31 - April 5, 2005. The
Congress (http://www.iups2005.org) is organized by the six member
societies of the U.S. National Committee of the IUPS, the American Physiological Society, the Society for Neuroscience, the
Microcirculatory Society, the Society of General Physiologists, the Biomedical Engineering Society, and the Society for
Integrative and Comparative Biology, under the auspices of the U.S. National Academy of Sciences.
The IUPS conference, held every four years, runs concurrently this year with Experimental Biology 2005 at the San Diego
Convention Center.
The American Physiological Society (APS), which is hosting IUPS, was founded in 1887 to foster basic and applied science,
much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes nearly 4,000
articles every year in its 14 peer-reviewed journals. In May, APS received the Presidential Award for Excellence in Science,
Mathematics and Engineering Mentoring (PAESMEM).
Editor's Note: For further information or to schedule an interview with a member of the research team, please contact Mayer
Resnick at the IUPS/APS newsroom @ 619-525-6228 (March 31-April 6), or 301-332-4402 (cell) or 301-634-7209 (office), or Stacy
Brooks at 240-432-9697 (cell) or 301-634-7253 (office).
A searchable online program for IUPS and EB is at faseb.org/meetings/eb2005/call/default.htm
Contact: Mayer Resnick
mresnick@the-aps.org
301-332-4402 (cell)
301-634-7209 (office, outside IUPS dates)
American Physiological Society
http://www.the-aps.org
IUPS/APS Newsroom March 29-April 6
San Diego Convention Center
Hall E Registration Area/Flex Unit
Telephone: 619-525-6228
"Paradoxul lui Mandela" poate arãta cã propensiunea osteoporozei începe în pre-teen ani - 'Mandela's Paradox' may show that osteoporosis propensity starts in pre-teen years - articole medicale engleza - startsanatate