Bone Health Could Be Impaired 25 Years Later in Extreme Preemies

By Scott Baltic

October 19, 2020

NEW YORK (Reuters Health) - Young adults who were born extremely preterm or with extremely low birthweight (EP/ELBW) may have impaired bone health many years later, compared with their term-born peers, according to a longitudinal study from Australian.

At age 25 years, the EP/ELBW group had significantly lower areal bone-mineral density and Z-score in the femoral neck as well as lower total hip Z-score than age-matched, normal-birthweight individuals, researchers report in Bone.

"Our findings have important clinical implications," Dr. Anjali Haikerwal of The Royal Women's Hospital, in Parkville,told Reuters Health by email. "Effective strategies for healthy lifestyle modifications, in particular nutrition and outdoor physical activity that maximize bone health, should be advocated early in life."

She added that to reduce the incidence of fractures in later life, young adults born preterm and their healthcare providers and family members should be informed about the importance of optimizing, and perhaps monitoring, bone health.

The Victorian Infant Collaborative Study has followed from birth 297 EP/ELBW individuals born in 1991-92, or around the beginning of the era of modern neonatal intensive care when survival rates of infants born EP/ELBW increased dramatically. This era has been marked particularly by the introduction of exogenous surfactant to treat respiratory distress syndrome.

The study defined EP/ELBW as birth at less than 28 weeks' gestation and with a weight below 1 kg, respectively.

At age 25, around the age of peak bone mass, 162 (55%) of the EP/ELBW participants and 129 (50%) of 260 controls had bone-health data available. The former were significantly shorter than the latter, by about 6 cm on average, and had more visceral adipose tissue, before and after adjusting for height and weight.

After adjustment for height and weight, the mean differences in bone-mineral density and Z-score at the femoral neck were 0.044 g/cm2 and 0.53, respectively; total hip Z-score was 0.35 points lower. These differences were both statistically and clinically important, according to the authors.

Compared with the control group, EP/ELBW males generally showed more bone deficits than females. In addition, they had less lean mass than controls.

Within the EP/ELBW group, early growth, male sex, height and lean mass, muscle measures, 25(OH)D levels, and bone-turnover markers were independently associated with bone mineral measures, structure and strength.

"Further follow-up of the EP/ELBW groups will determine if they have a heightened low-trauma fracture risk in later life," the authors note.

Dr. Unni Syversen, a professor of endocrinology at the Norwegian University of Science and Technology, in Trondheim, said the research "confirms previous studies showing an association between low birthweight/preterm birth and low peak bone mass."

"What's new," she told Reuters Health by email, "is that the study used peripheral quantitative computed tomography in addition to dual x-ray absorptiometry to assess bone parameters."

"Given the increasing number of survivors among those born with low birthweight, the findings of this study are of clinical significance," Dr. Syversen continued. "These individuals should be followed up to optimize their peak bone mass, as this is an important determinant of future fracture risk."

Dr. Thuy Mai Luu of the University of Montreal and CHU Sainte-Justine, in Canada, who specializes in fetal development and prematurity, told Reuters Health by email, "What this study adds is that certain potentially modifiable factors were associated with increased bone-mineral density, namely better child growth, increased vitamin D levels and increased lean mass. These are potentially all achievable targets for intervention to prevent morbidities that could result from reduced bone-mineral density."

"Pediatricians and family physicians are well positioned to encourage nutritional intake that will optimize growth and bone health (i.e., vitamin D and calcium)," Dr. Luu added. "Weight-bearing exercise should also be encouraged."

Neither Dr. Syversen nor Dr. Luu was involved with the study.

SOURCE: Bone, online September 17, 2020.