Tracking of Vitamin D Status and Bone Density

Kun Zhu, Michael Hunter, Jennie Hui, Kevin Murray, Alan James, Ee Mun Lim, Brian R Cooke, John P Walsh
Journal of the Endocrine Society, Volume 7, Issue 2, February 2023, bvac187
https://doi.org/10.1210/jendso/bvac187

Abstract

Context

The skeletal effects of vitamin D remain controversial and it is uncertain whether variation in serum 25-hydroxyvitamin D (25OHD) levels over time influences bone mineral density (BMD).

Objective

We evaluated longitudinal stability of serum 25OHD and associations with changes in BMD in participants aged 46–70 years at baseline.

Methods

We studied 3698 Busselton Healthy Ageing Study participants (2040 female) with serum 25OHD and dual-energy x-ray absorptiometry (DXA) BMD assessments at baseline and at ∼6 years follow-up. Restricted cubic splines were used to evaluate associations between changes in 25OHD and BMD.

Results

Mean season-corrected serum 25OHD was 81.3 ± 22.7 and 78.8 ± 23.1 nmol/L at baseline and 6 years, respectively, and showed moderate correlation (intraclass correlation coefficient: 0.724). Significant predictors of change in 25OHD concentration (Δ25OHD) included baseline 25OHD, change in body mass index and vitamin D supplementation at follow-up. Greater decline in serum 25OHD over time was associated with significantly greater reduction in BMD at total hip and femoral neck, but the magnitude of the differences was small (estimated differences 0.004 g/cm² and 0.005–0.007 g/cm², respectively, for lowest quartile of Δ25OHD compared with higher quartiles, adjusted for sex, baseline BMD, 25OHD, and demographics). No significant associations between Δ25OHD and lumbar spine BMD were observed. Increase in 25OHD levels was not associated with change in BMD.

Conclusions

In this predominantly vitamin D–replete middle-aged cohort, serum 25OHD showed moderate longitudinal stability. Declining serum 25OHD over time was associated with greater reduction in BMD at the total hip and femoral neck.

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