Nancy A. Melville

October 23, 2012

MINNEAPOLIS, Minnesota — In a study representing the longest tracking of bone mass measurements from childhood into adulthood to date, distal forearm bone mass was shown to partially track from youth into adulthood.

For the study, presented here at the American Society for Bone and Mineral Research (ASBMR) 2012 Annual Meeting, researchers in Sweden obtained baseline data available from 296 children who had participated in 3 studies that included bone mass measurements taken 26 to 29 years ago, between 1979 and 1985.

When invited to a follow-up study, the response rate was relatively high for such a long time period: 214 responded (72%). The 120 boys (mean baseline age, 10 years; range, 3 to 17 years) and 94 girls (mean baseline age, 11 years; range, 4 to 17 years) were evaluated after a mean of 28 years.

When remeasuring the participants, the researchers used the same single photon absorptiometry apparatus that was originally used in taking measurements on distal forearm cortical bone mineral content (BMC).

There were no significant differences in baseline BMC or bone mineral density (BMD). The results showed that BMC Z-scores in childhood correlated with the scores in adulthood for boys (r = 0.48) and girls (r = 0.64) (both P < .0001).

Similar patterns were seen among children who were 10 years or older at baseline (boys, r = 0.52; girls, r = 0.73; both P < .0001) and those who were younger than age 10 years (boys, r = 0.44; girls, r = 0.52; both P < .0001).

More than half (55%) of the children in the lowest quartile of BMC remained in the lowest quartile in adulthood (57% boys and 52% girls), and 66% with osteopenia in childhood had osteopenia in adulthood (56% boys and 79% girls).

The only child with osteoporosis had osteopenia as an adult.

"What we found was that BMC had a higher correlation coefficient than BMD, and girls had a higher correlation than boys, for BMC as well as BMD," said lead author Christian Buttazzoni, MD, from Skåne University Hospital Malmö, Lund University, in Sweden.

"While we cannot say of pubertal status, we divided into over and under 10 years, and when looking at the groups below 10 and over 10 years at baseline, the correlation coefficient was also higher for BMC than BMD and higher for girls than boys."

"We believe this is probably due to the fact that BMC only reflects bone mineral while BMD also includes bone size," he noted.

The results suggest that the reliability of such pediatric data in predicting low BMD in adulthood appears weak, Dr. Buttazzoni said.

"The study infers that, at least in terms of forearm bone mass in children, such information seems to be of limited value in the clinical situation to identify individuals who will have low distal forearm bone mass in adulthood," he said.

Bone expert Ego Seeman, MD, from Austin Health, University of Melbourne, Australia, suggested that more details could provide a bigger picture and better understanding of the relationship between bone mass in childhood and in later life.

"What’s interesting about this data is the lack of tracking and the weaker correlations, but what would be really useful to see would be a graph plotting everyone, showing, for instance, what proportion of people in the upper quartile or the lowest quartile were still there in adulthood, and what proportion crossed over," said Dr. Seeman.

"Then the more interesting question of why they are changing could be addressed, and if they are changing, is that because there is a changing relationship between the size of the bone and the amount of bone within it?"

"If bone mass goes up, for instance, but bone size doesn't change, the density would be going up. So if you can set down those morphological features you may find some interesting things."

 Dr. Buttazzoni and Dr. Seeman have disclosed no relevant financial relationships.

American Society for Bone and Mineral Research (ASBMR) 2012 Annual Meeting. Abstract 1025. Presented October 15, 2012.