Is 25(OH)D Associated with Cognitive Impairment and Functional Improvement in Stroke? A Retrospective Clinical Study

Background

In recent years, vitamin D deficiency has been suggested as a risk factor for ischemic stroke and stroke severity in both animal models and clinical studies. In this retrospective study, we investigated the relationship between 25-hydroxyvitamin D [25(OH)D] levels and functional outcomes in stroke patients during neurological rehabilitation program. We also investigated whether there is an association between 25(OH)D levels and cognitive impairment.

Methods

The study included the medical records of 120 stroke patients who participated in a neurological rehabilitation program. The motor and cognitive components of the Functional Independence Measurements of all patients at admission and discharge were recorded. The Functional Ambulatory Scale was used to assess motor functional status, and the Turkish-validated version of the minimental state examination test was used to assess cognitive status.

Results

A significant correlation was found between 25(OH)D level and cognitive impairment among patients who had ischemic strokes. High levels of 25(OH)D were associated with greater functional gain during the rehabilitation program in both ischemic stroke patients and hemorrhagic stroke patients.

Conclusions

High 25(OH)D levels might be associated with greater functional improvement and with less cognitive impairment in stroke patients.

Introduction

The hormone vitamin D is essential for calcium metabolism and bone homeostasis. It has also been reported that vitamin D plays an important role in immune modulation, cell proliferation and differentiation, and regulation of cell growth.¹ Generally speaking, vitamin D is biologically inactive; to be activated, it must be hydroxylated to 25-hydroxyvitamin D [25(OH)D] in the liver and to 1,25(OH)D in the kidney, which has the highest affinity for vitamin D receptors (VDRs). Although 1α hydroxylation of vitamin D occurs in the kidney, it has been shown that this process might occur locally in different cells and organs as well.² Thus, measuring 25(OH)D is the best method for estimating the entire vitamin D status.2, 3

Poor vitamin D status is a public health problem, and low levels of this vitamin have been associated with cardiovascular disease and reported as a predictive factor for stroke.1, 4 Experimental studies have shown that vitamin D can prevent neurons from excitotoxic injury⁵ and that VDRs are activated by cerebral ischemia in animal models and in human stroke patients.⁶

Although several studies have reported a relationship between low vitamin D levels and an increased risk of stroke, only a few studies have reported low vitamin D levels as a predictor of high mortality and poor functional outcomes in the early stages of stroke.⁷ In this study, we investigated whether functional outcomes after neurological rehabilitation and cognitive impairment in individuals with stroke correlated with their plasma 25(OH)D levels. We hypothesized that low 25(OH)D levels in stroke patients are associated with less functional gain after neurological rehabilitation and greater cognitive impairment.