Serum 25-hydroxyvitamin D, vitamin D receptor and vitamin D binding protein gene polymorphisms and risk of dementia among older adults with prediabetes.

BACKGROUND: The association between vitamin D and dementia risk in those with prediabetes remains uncertain. We aimed to evaluate the association of serum 25-hydroxyvitamin D (25OHD) with incident dementia among older adults with prediabetes, and examine whether Apolipoprotein E (APOE) genotypes, vitamin D receptor (VDR) and vitamin D binding protein (VDBP) gene polymorphisms may modify this association.

METHODS: 34,237 participants aged ≥60 with prediabetes (HbA1c <6.5% and ≥5.7%) and without dementia at baseline were included from the UK Biobank. Serum 25-hydroxyvitamin D (25OHD) was measured using chemiluminescent immunoassay method. The primary outcome was incident all-cause dementia. Secondary outcomes included incident Alzheimer disease (AD) and vascular dementia, respectively. The VDR and VDBP gene polymorphisms included single nucleotide polymorphisms of rs7975232, rs1544410, rs2228570, rs731236, and rs7041, rs4588, respectively.

RESULTS: During a median follow-up of 11.8 years, 941 (2.7%) participants developed incident all-cause dementia. Overall, serum 25OHD was inversely associated with all-cause dementia (Per SD increment, adjusted HR: 0.82; 95%CI: 0.75, 0.89). Similar trends were found for incident AD and vascular dementia. Furthermore, there was a stronger inverse relationship between serum 25OHD and all-cause dementia among VDR rs7975232 C allele non-carriers (P-interaction<0.05). However, APOE Ɛ4, other VDR and VDBP gene polymorphisms did not significantly modify the relation of serum 25OHD with incident all-cause dementia (All P-interactions >0.05).

CONCLUSIONS: There was an inverse association between serum 25OHD and incident dementia among older adults with prediabetes, especially in VDR rs7975232 AA allele carriers.