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

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

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

Very low birth weight was defined as birth weight less than 3.31 lb.

The researchers determined each participant’s BMD using DEXA. 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 (95% CI: 0.28-0.75); the average femoral neck Z score was –0.56 (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 very low birth weight group, the differences remained statistically significant, according to a press release.

“Furthermore, 44% of the very low birth weight 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, MD, PhD, of Leiden, Netherlands, wrote in his summary of the findings.

“This finding may predict symptomatic osteoporosis and increased fracture rates,” the researchers wrote.

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

Hovi P. PloS Med. 2009;doi:10.1371/journal.pmed.1000135.