Reduced BMD in adults with very low birth weight may lead to osteoporosis, related fractures

Individuals who had a very low birth weight (VLBW) had significantly less bone mineral density (BMD) at the adult age when they should normally reach peak bone mass compared to same-aged adults born at term, Finnish researchers found.

In the Helsinki Study of Very Low Birth Weight Adults, a multidisciplinary cohort study designed to see if health problems in VLBW babies persist into adulthood, Petteri Hovi, MD, and colleagues evaluated 144 adults between 18.5 and 27.1 years old born in the greater Helsinki area between 1978 and 1985 with VLBW. They compared the group’s skeletal health to 139 adults matched for age, gender and birth hospital.

Hovi and colleagues defined VLBW babies as those whose birth weight was less than 3.31 pounds.

The researchers determined each participant’s BMD using dual-energy X-ray absorptiometry. They calculated Z scores representing the participants’ lower lumbar spine and hip BMD, defining reduced BMD as a Z score of -1.0 units or less.

The study group’s average Z score for the lower lumbar spine was -0.51 unit (95% CI: 0.28-0.75); the average femoral neck Z score was -0.56 unit (95% CI: 0.34-0.78) for areal BMD. After adjusting for the shorter adult height and less intense level of exercise practiced in the VLBW group, the differences remained statistically significant, according to a press release.

“Furthermore, 44% of the VLBW participants, but only 26% of the term-born participants, had a lumbar spine Z score of -1.0 or less,” study editor Tom W.J. Huizinga, of Leiden, Netherlands, wrote in his summary of the findings.

Hovi and colleagues said in their abstract, “This finding may predict symptomatic osteoporosis and increased fracture rates.”

In addition, increased vigilance in osteoporosis prevention may be warranted in VLBW children who become adults with low BMD, they noted.

Researchers said the main limitations of the study were the final cohort may not be representative of the original cohort of individuals born in Helsinki-area hospitals; comparisons they made were only internal; and they measured BMD just once, which reduced the chances of associating lower BMD with other possible causes, such as delayed skeletal maturing in the VLBW group.

Reference:
Hovi P, Andersson S. Järvenpää A-L, et al. Decreased bone mineral density in adults born with very low birth weight: A cohort study. PloS Med. 2009;6(8):e1000135. DOI: 10.1371/journal.pmed.1000135.