Can low vitamin D levels cause increased risk of cognitive decline in older diabetic patients? Recent research evidence suggests this might be so. The authors of the study, published March 2020 in Experimental Gerontology, reaffirm the association between low vitamin D and increased inflammatory biomarkers such as C-reactive protein, white blood cell count, and plasma fibrinogen. They also explored what role low vitamin D may play in elderly diabetic patients at risk for developing mild cognitive impairment. 

Lead author, Malgorzata Gorska-Ciebiada, affiliated with the Department of Propaedeutics of Lifestyle Diseases, and Maciej Ciebiada, Department of General and Oncological Pneumology, Medical University of Lodz, Poland, compared the levels of vitamin D (25-hydroxvitamin D; 25[OH]D) and high-sensitivity C-reactive protein (hsCRP) in two groups of elderly patients. One group had type 2 diabetes (T2DM) and mild cognitive impairment (MCI) (n = 62), and the other group had only T2DM (n = 132). Additionally, the researchers sought to identify which factors (including vitamin D levels and hsCRP) are associated with MCI in elderly patients with T2DM. While vitamin D deficiency is known to play a role in various neuropsychiatric disorders, the potential enhanced effects of vitamin D deficiency in the presence of increased inflammatory biomarkers has been less clear.  

The 194 study participants were recruited from a previous study and included diabetic patients aged 65 years and older. The study excluded those diagnosed with dementia, depression, or substance abuse; those taking vitamin D supplements; those with a neoplasm or severe visual, mobility, or motor coordination impairments; and those with a history of head trauma, certain brain diseases, or severe neurological or psychiatric illness. The researchers conducted a cross-sectional study in which a single visit was divided into two phases. The first phase included a complete physical examination, vitals, and laboratory samples, and the second visit consisted of a questionnaire to gather demographic data, followed by cognitive testing.  

When compared with the control group, patients with MCI had a significantly decreased serum 25[OH]D level (P <.001) and significantly increased hsCRP levels (P <.001). The researchers reported that, as they hypothesized, in the group of patients with MCI, lower serum 25[OH]D levels were negatively correlated with hsCRP level (r = –0.28, P = .028), and serum 25[OH]D concentrations were positively correlated with Montreal Cognitive Assessment (MoCA) scores (r = 0.31, P = .016).  

In the group of patients with MCI, hsCRP concentration was highly correlated with A1C level (r = 0.55, P <.001) and was inversely correlated with MoCA score (r = –0.59, P <.001). The authors concluded, “Higher hsCRP level and lower 25-hydroxyvitamin D may be regarded as a state of cognitive impairment in elderly patients with T2DM. Further prospective larger studies should be conducted to check the association between decreased vitamin D and risk of cognitive decline and to clarify whether this association may be mediated by systemic inflammation.”

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