Endocrine Abstracts

Background: Bone health can be affected in (young) adults with Cystic Fibrosis (CF) due to different risk factors in childhood. We aimed to analyze the prevalence of low bone mineral density (BMD) during childhood in patients with CF, its risk factors and course in time.

Methods: A longitudinal prospective cohort study was performed in children with CF aged 8-18. Anthropometric, DEXA scans and endocrine data were collected. BMD z-scores were adjusted for height. Low BMD and too low BMD scores were defined as a z-score <-1 and <-2 respectively. We analyzed if BMD was associated to body mass index standard deviation score (BMI-SDS), vitamin D status, lung function (FEV1%) and cystic fibrosis related diabetes. Patients on corticosteroids in the last 6 months were excluded.

Results: One hundred-and-two children with CF (50 boys, 52 girls) were included, with a mean age of 13.0 ± 3.23 yrs. The mean BMI z-score was -0.04 ± 1.10 and mean FEV1%-value was 85.7 ± 18.5. Mean adjusted BMD z-scores for lumbar spine (LS) and total body less head (TBLH) were 0.05 ± 1.13 and 0.14 ± 1.08 respectively, with no differences between sexes. Eighteen children (17.6%) had (too) low LS BMD, and 17 (16.7%) had (too) low TBLH BMD z-scores. In multiple linear regression analysis, TBLH-BMD z-scores were positively associated to BMI-SDS and FEV1%-values (P=0.004) and LS-BMD z-scores were positively associated to BMI-SDS (P=0.007). Forty-nine children (22 boys, 27 girls) had a second DXA-scan on average 2.15 ± 0.37 years after the 1^st scan at a mean age of 14.9 ± 3.09 yrs. A significant mean decrease was seen in TBLH BMD-z score of -0.70 ± 0.76 (P<0.001). After multiple testing, LS BMD z-scores were positively associated to BMI-SDS (P=0.003).

Conclusion: Most children with CF have normal BMD, however BMD seems to decrease in time. To ensure optimal bone health, nutritional status must be monitored especially in children with decreased lung function.