Relationship between homocysteine levels, vitamin D and cognitive function in persons with intellectual disability

Objectives The aim of the article is to determine the relationship between homocysteine in the plasma, vitamin D (VitD) in the serum and cognitive abilities in persons with mild intellectual disability (ID) in different age groups. Methods In a cross-sectional, observational study including younger and older participants with mild ID, a cognitive assessment was performed using the Montreal Cognitive Assessment (MoCA), and blood samples were taken to assess plasma homocysteine and serum VitD levels. Results A total of 60 persons with mild ID were included in the study, of whom 30 were aged 9–16 and 30 were aged 35–62 years old. Increased plasma homocysteine values were detected in 85% of cases and reduced serum VitD levels in 90% of cases. Older participants had significantly higher homocysteine values than younger ones (t(58) = −4.19; p = 0.00; d = 1.082), while younger participants had significantly more pronounced VitD deficiency than older ones (t(58) = −3.91; p = 0.00; d = 1.011). A significant correlation between cognition and VitD values was found in older participants (r = −0.424, p = 0.020). Conclusions A substantial proportion of individuals with ID, both children and adults, have increased total homocysteine (tHcy) plasma levels and insufficient VitD serum, but the clinical significance of these findings remains to be determined. Homocysteine and VitD have not been found to have a protective effect on cognition among persons with mild ID.