E-Poster Presentation 30th Australian and New Zealand Bone and Mineral Society Annual Scientific Meeting 2020

Population vitamin D stores are increasing in Tasmania and this is associated with less BMD loss over 10 years (#121)

Michael Thompson 1 , Dawn Aitken 1 , Saliu Balogun 1 , Flavia Cicuttini 2 , Graeme Jones 1
  1. Menzies Institute for Medical Research, University of Tasmania, Hobart, Tasmania, Australia
  2. Musculoskeletal Unit, Monash University, Melbourne, Victoria, Australia

Introduction

Vitamin D deficiency is a prevalent, modifiable determinant of poor musculoskeletal health. Public health interventions have aimed to improve population vitamin D status. However, there is minimal longitudinal data assessing whether these programs have improved vitamin D sufficiency or evaluating the skeletal health outcomes of maintaining or achieving vitamin D sufficiency.

 

Methods

Community-dwelling adults aged 50-80 years had 25-hydroxyvitamin D (25(OH)D) assessed by radioimmunoassay at baseline (n=1096), 2.5 (n=870) and 10 (n=565) years in a Tasmanian population-based prospective cohort study. Sun exposure was quantified by questionnaire, supplement use at clinic review and BMD by DXA. 25(OH)D <50nmol/L was considered deficient.

 

Results

Over 10 years mean 25(OH)D increased (52.4±18.7 to 62.5±23.5 nmol/L, p<0.001) and the percentage of vitamin D deficient participants decreased (48.5% to 29.8%, p<0.001). Participants with baseline deficiency had larger 25(OH)D increases than baseline sufficient participants (19.2±25.3 vs 1.6±23.3 nmol/L, p<0.001). The proportion of participants taking vitamin D supplements increased (2.3% to 37.1%, p<0.001). Longitudinal change in 25(OH)D was associated with baseline summer (β=1.46, p<0.001) and winter (β=1.29, p=0.003) sun exposure, change in summer (β=1.27, p=0.002) and winter (β=1.47, p<0.001) sun exposure and vitamin D supplement use (β=24.9-34.8, p<0.001). Participants who were always vitamin D sufficient retained significantly more BMD at all sites (β=0.019 – 0.030, p=0.006 – 0.047 vs always deficient group). Participants who achieved vitamin D sufficiency had greater BMD gains at the lumbar spine (β=0.019, p=0.02) and similar BMD outcomes elsewhere compared to those who were always sufficient.

 

Conclusions

Cohort 25(OH)D concentration increased and vitamin D sufficiency was associated with less BMD loss over 10 years. This suggests that (1) intervention can improve population vitamin D status, (2) vitamin D sufficiency may ameliorate BMD loss in older adults and (3) vitamin D repletion of deficient individuals can achieve similar longitudinal BMD outcomes as persistent sufficiency.