Correlation Between Serum 25-hydroxyvitamin D Level and Cognitive Function Among the Elderly in Enugu State, Nigeria

Abstract

<i>Background</i>: Low serum vitamin D is now implicated in many disease conditions among the elderly including cognitive impairment. Cognitive impairment is a common disease among elderly people causing much financial and social burden to the elderly, their families and caregivers. Therefore, the study aimed to determine the relationship between serum 25-hydroxyvitamin D (25(OH)D) concentration and cognitive function among elderly people in Enugu State, South-eastern Nigeria. <i>Methods</i>: This was a cross-sectional survey of subjects aged ≥ 60 years with cognitive impairment in communities and old People’s home in Enugu State in Nigeria and age- and sex-matched controls. The subjects were further divided into those with severe cognitive impairment and those with mild cognitive impairment using the Mini-Mental State Examination (MMSE). Serum 25(OH)D and parathyroid hormone (PTH) were assayed by enzyme-linked immune-sorbent assay while serum calcium, inorganic phosphate, and albumin were determined using the spectrophotometric method. Student t-test was used to compare mean values obtained, while Pearson correlation was used to determine relationships between continuous data. A p-value<0.05 was considered to be statistically significant. <i>Result</i>: One hundred and four (104) patients comprising of 58 males and 46 females were recruited for the current study. Among the study subjects compared to those of the controls, there were significantly decreased levels of serum 25(OH)D (p=0.0001) and the adjusted calcium (p=0.0001) concentrations but significantly increased level of serum PTH (p=0.0001) and inorganic phosphate (p=0.005) concentrations. Also, the mean values of serum 25(OH)D and adjusted calcium were significantly lower, serum PTH values were significantly higher while serum inorganic phosphate concentrations showed no significant difference for those with severe cognitive impairment when compared to values of those with mild cognitive impairment and controls. Additionally, there was also significant positive correlations between serum 25(OH)D and cognitive function (r=0.504, ρ<0.05). <i>Conclusion</i>: The study findings suggest that decreased serum Vitamin D concentration is associated with diminished cognitive function among the elderly and vice versa. Hence, the determination of Vitamin D status among elderly patients presenting with impairment of cognitive function is highly recommended. However, further studies are needed to validate findings from the present study.