Population Vitamin D Stores Are Increasing in Tasmania, and This Is Associated With Less BMD Loss Over 10 Years

Context Vitamin D deficiency is a common, modifiable determinant of musculoskeletal health. Objective There are limited data that examine the longitudinal change in population 25-hydroxyvitamin D (25[OH]D) and none that evaluate the long-term skeletal outcomes of longitudinal vitamin D status. Methods A prospective cohort analysis was conducted of community-dwelling adults aged 50 to 80 years who had 25(OH)D assessed by radioimmunoassay and bone mineral density (BMD) by dual-energy x-ray absorptiometry at baseline (n = 1096), 2.5 (n = 870), and 10 (n = 565) years. Sun exposure was quantified by questionnaire and supplement use at clinic review. 25(OH)D less than 50 nmol/L was considered deficient. Participants were provided with their 25(OH)D results. Results Over 10 years 25(OH)D increased (52.2 +/- 17.0 to 63.5 +/- 23.6 nmol/L, P < .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 < .001). Longitudinal change in 25(OH)D was associated with baseline summer (beta = 1.46, P < .001) and winter (beta = 1.29, P = .003) sun exposure, change in summer (beta = 1.27, P = .002) and winter (beta = 1.47, P < .001) sun exposure, and vitamin D supplement use (beta = 25.0-33.0, P < .001). Persistent vitamin D sufficiency was associated with less BMD loss at the femoral neck (beta = 0.020, P = .027), lumbar spine (beta = 0.033, P = .003), and total hip (beta = 0.023, P = .021) compared to persistent vitamin D deficiency. Achieving vitamin D sufficiency was associated with less BMD loss at the lumbar spine (beta = 0.045, P < .001) compared to persistent vitamin D deficiency. Conclusions Population 25(OH)D concentration increased because of a combination of increased sun exposure and supplement use. Maintaining or achieving vitamin D sufficiency was associated with less BMD loss over 10 years.

Automated summary

The longitudinal increase in population 25(OH)D concentration is attributed to increased sun exposure and supplement use. Maintaining or achieving vitamin D sufficiency is associated with less bone mineral density loss over 10 years.