Vitamin D-related changes in intracranial volume in older adults: a quantitative neuroimaging study.

OBJECTIVES: Vitamin D is involved in skeletal and brain health. Recently, serum 25-hydroxyvitamin D (25OHD) concentration was found to be inversely correlated with intracranial volume in younger adults. Since hypovitaminosis D is most common in older adults, our objective was to determine whether this inverse correlation between 25OHD concentration and intracranial volume also occurred in older adults. STUDY DESIGN: Cross-sectional study. MAIN OUTCOME MEASURES: One hundred and ten Caucasian older community-dwellers (mean, 71.7±5.7 years; 45.5% female) received a blood test and an MRI of the brain at the same period. The intracranial volume and the subvolumes of cerebrospinal fluid, total brain, infratentorial brain, supratentorial brain, total white matter, total gray matter, cortical gray matter and subcortical gray matter were measured using FreeSurfer volumetry on T1-weighted images. Vitamin D insufficiency was defined as serum 25OHD\u3c50nmol/L. Age, gender, body mass index, education level, use of vitamin D supplements, season of evaluation, serum concentrations of calcium and thyroid stimulating hormone were used as covariables in the analysis. RESULTS: We found that participants with vitamin D insufficiency (n=41) had greater intracranial volume than those without (1555.0±1379.2cm(3) versus 1488.0±167.4cm(3), P=0.033). Serum 25OHD concentration was cross-sectionally associated with decreased intracranial volume in mm(3) (unadjusted β=-1194.4, P=0.028), even after adjustment for covariables (adjusted β=-994.3, P=0.048). We found an inverse correlation of serum 25OHD with intracranial volume (r=-0.21, P=0.028) and the volume of white matter (r=-0.20, P=0.033). The other subvolumes did not correlate with serum 25OHD concentration. CONCLUSIONS: Serum 25OHD concentration was independently and inversely associated with intracranial volume in older adults