Endocrine Abstracts

Background: Vitamin D deficiency is very common in older persons. It is not clear how serum 25-hydroxyvitamin D (25(OH)D) levels change during aging.

Objective: To examine longitudinal changes in serum 25(OH)D levels in two representative cohorts of Dutch older persons during 6 and 13 years of follow-up, respectively.

Methods: Data of the Longitudinal Aging Study Amsterdam (LASA) were used, an ongoing cohort study in older persons. Two different cohorts were included: i) younger cohort: aged 55–65 years at baseline, n=738, follow-up of 6 years; ii) older cohort: aged 65–88 years at baseline, n=1320, follow-up of 13 years. Linear mixed models were used to analyze the longitudinal change in serum 25(OH)D in both cohorts. Age and body mass index were added to the model. Seasonal variation was modeled by adding a cosine and sine function with a period of 1 year to the model.

Results: At baseline, average levels were 56.5 nmol/l in the younger cohort and 51.1 nmol/l in the older cohort. The seasonal variation was ±11 nmol/l in the younger cohort, and ±7 nmol/l in the older cohort. In the younger cohort, a longitudinal increase in mean serum 25(OH)D levels of 5 nmol/l in 6 years was observed after adjustment for age, sex, season and body mass index (BMI). In the older cohort, a longitudinal decrease in mean serum 25(OH)D levels of 5 nmol/l in 13 years was observed.

Conclusions: Serum 25-hydroxyvitamin D levels changed during follow-up with increasing levels in persons aged 55–65 years, and decreasing levels in persons aged 65–88 years. This implicates that vitamin D supplementation becomes more important in older age groups.

Declaration of interest: I fully declare a conflict of interest. Details below:

Funding: This work was supported, however funding details unavailable.