Serum 25-hydroxyvitamin D level and the risk of mild cognitive impairment and dementia: the Korean Longitudinal Study on Health and Aging (KLoSHA)

Vitamin D, Alzheimer's disease and related dementia

Vitamin D has been proposed as a potential strategy to mitigate age-related cognitive decline and dementia, including Alzheimer's dementia, the predominant type of dementia. Rodent studies have provided insight into the potential mechanisms underlying the role of vitamin D in Alzheimer's disease and dementia. However, inconsistencies with respect to age, sex, and genetic background of the rodent models used poses some limitations regarding scientific rigor and translation. Several human observational studies have evaluated the association of vitamin D status with cognitive decline and dementia, and the results are conflicting. Randomized clinical trials of vitamin D supplementation have included cognitive outcomes. However, most of the available trials have not been designed specifically to test the effect of vitamin D on age-related cognitive decline and dementia, so it remains questionable how much additional vitamin D will improve cognitive performance. Here we evaluate the strengths and limitations of the available evidence regarding the role of vitamin D in AD, cognitive decline, dementia.

Is There a Role of Vitamin D in Alzheimer's Disease?

Alzheimer's disease (AD) represents the most prevalent type of neurodegenerative dementia and the sixth leading cause of death worldwide. The so-called "non-calcemic actions" of vitamin D have been increasingly described, and its insufficiency has already been linked to the onset and progression of the main neurological diseases, including AD. Immune-mediated Aβ plaque's phagocytosis and clearance, immune response, oxidative stress, and mitochondrial function are all influenced by vitamin D, and these functions are considered relevant in AD pathogenesis. However, it has been shown that the genomic vitamin D signaling pathway is already impaired in the AD brain, making things more complicated. In this paper, we aim to summarise the role of vitamin D in AD and review the results of the supplementation trials in AD patients.

Serum Vitamin D Status and Cognitive Function in Iranian Older Adults: Evidence from the Birjand Longitudinal Aging Study

BACKGROUND

There is evidence of the role of vitamin D deficiency in cognitive decline. However, the results of studies regarding the relationship between the reduction of vitamin D concentrations and cognitive impairment are heterogeneous.

OBJECTIVES

We aimed to answer the question of whether vitamin D deficiency is associated with cognitive decline in older adults.

METHODS

In this cross-sectional study, the baseline data of the Birjand Longitudinal Aging Study (BLAS) were analyzed. Of 1420 participants in the BLAS, 1219 participants aged ≥60 y old were included in the present study. Serum concentrations of 25-hydroxyvitamin D [25(OH)D] were measured by the enzyme-linked immunosorbent assay method. The 6-item Cognitive Impairment Test (6-CIT), Mini-Mental State Examination (MMSE), Category Fluency Test (CFT), and Abbreviated Mental Test Score (AMTS) were used to assess cognitive function. Multiple logistic regression analysis, adjusted for potential confounders, was employed to estimate the association between cognitive function and 25(OH)D concentrations.

RESULTS

Among study participants, 905 (74.24%) had sufficient vitamin D concentrations (≥20 ng/ml), 209 (17.15%) had insufficient vitamin D concentrations (12-20 ng/ml), and 105 (8.61%) had vitamin D deficiency (<12 ng/ml). There was no significant correlation between serum 25(OH)D concentrations and scores of 6-CIT (P = 0.279), AMTS (P = 0.181), MMSE (P = 0.118), and CFT (P = 0.259). Also, the prevalence of cognitive impairment had no significant relationship with vitamin D status. Finally, in the multiple logistic regression analysis, there was no association between the insufficient or deficient concentrations of 25(OH)D and impaired cognitive function both before and after adjustment for various cofounders.

CONCLUSIONS

The present study found no significant association between vitamin D status and cognitive impairment.

Vitamin D3 supplementation ameliorates cognitive impairment and alters neurodegenerative and inflammatory markers in scopolamine induced rat model

A multifaceted approach can be effective for the treatment of dementia including the most common form, Alzheimer's disease (AD). However, currently, it involves only symptomatic treatment with cholinergic drugs. Beneficial effects of high Vitamin D₃ levels or its intake in the prevention and treatment of cognitive disorders have been reported. Thus, the present study examined the preventive effect of Vitamin D₃ (Calcitriol) supplementation on cognitive impairment and evaluated its impact on the accumulation or degradation of Aβ plaques. A single intraperitoneal injection of scopolamine was used to induce cognitive impairment in rats. Treatment of Vitamin D₃ was provided for 21 days after the injection. Various behavioral parameters like learning, spatial memory and exploratory behavior, biochemical alterations in the brain homogenate and histology of the hippocampus were investigated. Our results indicated that scopolamine-induced rats depicted cognitive deficits with high Aβ levels and hyperphosphorylated tau proteins in the brain tissue, while Vitamin D supplementation could significantly improve the cognitive status and lower these protein levels. These results were supported by the histopathological and immunohistochemical staining of the hippocampal brain region. Furthermore, mechanistic analysis depicted that Vitamin D supplementation improved the Aβ protein clearance by increasing the neprilysin levels. It also reduced the accumulation of Aβ plaques by lowering neuroinflammation as well as oxidative stress. The present findings indicate that Vitamin D₃ supplementation can ameliorate cognitive deficits and thereby delay AD progression by increasing Aβ plaque degradation, reducing inflammation and oxidative stress.

Current Evidence on the Association of Micronutrient Malnutrition with Mild Cognitive Impairment, Frailty, and Cognitive Frailty among Older Adults: A Scoping Review

Micronutrient malnutrition is thought to play an important role in the cause of cognitive impairment and physical frailty. The purpose of this scoping review was to map current evidence on the association between micronutrient deficiency in blood and mild cognitive impairment, frailty, and cognitive frailty among older adults. The scoping review was conducted based on the 2005 methodological framework by Arksey and O'Malley. The search strategy for potential literature on micronutrient concentration in blood and cognitive frailty was retrieved based on the keywords using electronic databases (PubMed, Cochrane Library, Google Scholar, Ovid, and Science Direct) from January 2010 to December 2021. Gray literature was also included in the searches. A total of 4310 articles were retrieved and 43 articles were incorporated in the review. Findings revealed a trend of significant association between low levels of B vitamins (folate and vitamin B12), vitamin D, vitamin A, vitamin E, omega 3 fatty acid, and albumin, and high homocysteine levels in blood with an increased risk of mild cognitive impairment among older adults. The results also indicated that low vitamin D levels, albumin, and antioxidants (lutein and zeaxanthin) in blood were significantly associated with frailty among older adults, while β-cryptoxanthin and zeaxanthin in blood were inversely associated with the risk of cognitive frailty. Vitamin D and antioxidants seemed to be targeted nutrients for the prevention of cognitive frailty. In conclusion, a wide range of micronutrient deficiency was associated with either mild cognitive impairment or frailty; however, little evidence exists on the dual impairment, i.e., cognitive frailty. This scoping review can serve as preliminary evidence for the association between micronutrient deficiency in blood and mild cognitive impairment, frailty, and cognitive frailty among older adults and prove the relevancy of the topic for future systematic reviews.

Cognitive deficits in primary hyperparathyroidism - what we know and what we do not know: A narrative review

Classic symptoms of primary hyperparathyroidism (PHPT) are seen in approximately 20% of patients. While features such as kidney stones and skeletal disease are often highlighted as directly related to the disease, others can be even more prevalent. For example, cognitive dysfunction and reduced quality of life are common complaints in many patients, even among those who are classified as being asymptomatic. The pathophysiology of PHPT involves the impact of excess parathyroid hormone (PTH) on calcium metabolism. Referencing putative neurocognitive issues, many animal studies have illustrated the potential roles of PTH and PTH receptors in the brain. Functional imaging and pre-and post-parathyroidectomy studies have suggested a link between the neuronal impact of elevated PTH levels on specific functional aspects of the central nervous system, such as cognition. Confounding a direct role for PTH are hypercalcemia and vitamin D deficiency, both of which could conceivably alter CNS function in PHPT. The lack of strong evidence that parathyroidectomy improves cognition in patients with PHPT raises the question as to whether parathyroid surgery should be recommended on this basis alone. This narrative review summarizes the available literature on neurocognitive function in PHPT.

Vitamin D as a possible biomarker of mild cognitive impairment in parkinsonians

INTRODUCTION

Mild Cognitive Impairment in Parkinson's Disease (PD-MCI) is a transitional state between normal cognition and dementia. Cross-sectional studies revealed that low Vitamin D levels were associated with worse performance on cognitive tests in Parkinson's Disease. The present longitudinal study aimed to examine the relationship between serum 25-hydroxyvitamin D [25(OH)D] levels at baseline and possible development of PD-MCI at 24 and 48 months.

MATERIALS AND METHODS

Sixty untreated, de novo PD patients underwent clinical and cognitive evaluations and measurement of serum 25(OH)D at baseline assessment (T0). After 24 (T1) and 48 months (T2), cognitive status (presence or absence of PD-MCI) of PD patients were re-evaluated.

RESULTS

Vitamin D insufficiency occurred in 93.3% at T0. At T1, significant differences among patients with PD-MCI at both baseline and follow-up, patients with PD-MCI at follow-up and patients who never developed PD-MCI were found on age, age at onset of PD, and education; no significant difference was found on vitamin D levels at T0. A binary logistic regression analysis showed that a lower level of 25(OH)D at T0 (B= -0.158, Wald= 5.280, p = 0.022, Exp (B)=0.854; CI 95%: 0.746-0.977) and lower education (B= -0.214, Wald= 3.859, p = 0.049, Exp (B)=0.807; CI 95%: 0652-1.000) were predictors of PD-MCI occurrence at T2.

DISCUSSION

Our results demonstrated that a lower level of 25(OH)D is conceivable as a biomarker of development of PD-MCI throughout the disease. Early diagnosis of Vitamin D insufficiency and its management might be useful to prevent cognitive decline in PD patients.

Low Serum 25-Hydroxy Vitamin D (25-OHD) and Hepatic Encephalopathy in HCV-Related Liver Cirrhosis

BACKGROUND

Patients with liver cirrhosis experience a large variety of metabolic disorders associated with more hepatic decompensation. Hepatic encephalopathy (HE) is a significant complication in liver cirrhosis patients, presenting a wide spectrum of neuropsychological symptoms. A deficiency of 25-hydroxy vitamin D (25-OHD) in the general population is associated with a loss of cognitive function, dementia, and Alzheimer's disease. Aim of the Study. Our study aims to check the relationship between low serum 25-OHD and HE in patients with HCV-related liver cirrhosis and assess its link with patient mortality. Patients and Methods. This study was observationally carried out on 100 patients with HCV-related liver cirrhosis. The patients were divided into 2 groups: Group A-included 50 HCV-related cirrhotic patients with HE, and Group B-included 50 HCV-related cirrhotic patients without HE. Assessment of disease severity using the end-stage liver disease (MELD) model and Child Turcotte Pugh (CTP) scores were done, and 25-OHD levels were measured. Comparison of vitamin D levels in different etiologies and different CTP categories was made using one-way ANOVA. Pearson's correlation between the level of vitamin D and other biomarkers was applied.

RESULTS

There was a statistically significant Vitamin D level difference between the two groups. A lower level of vitamin D was observed in the HE group where the severe deficiency was 16%, while it was 6% in the other group and the moderate deficiency was 24% in HE group as compared to 10% in the other group. The insufficient vitamin D level represented 46% of the non-HE group while none of the HE group falls in this category. Vitamin D level was statistically higher in Grade 1 HE than in Grade 2 which is higher than in Grades 3 to 4. Vitamin D level was also significantly higher in those who improved from HE as compared to those who died.

CONCLUSION

The lower levels of 25-OHD were associated with the higher incidence of HE in cirrhotic HCV patients. The worsening vitamin D deficiency was associated with increased severity of the liver disease, so vitamin D may be considered a prognostic factor for the severity of liver cirrhosis and high mortality rate in HE patients.

Vitamin D in the development and progression of alzheimer's disease: implications for clinical management

INTRODUCTION

Although the pathophysiological bases of Alzheimer's disease (AD) remain incompletely understood and disease-modifying therapies are not available, intervention on modifiable risk factors is warranted. Research on nutrition and dietary components is challenging and controversies still persist about the role of micro- and macronutrients and health outcomes in dementia. Importantly, results of preclinical investigations have shown that vitamin D triggers different neural pathways that may be protective against these neurodegenerative mechanisms, including the deposition of amyloid plaques, inflammatory processes, neurofibrillary degeneration, glutamatergic excitotoxicity, excessive intraneuronal calcium influx, and oxidative stress, although its relationship with AD still needs to be fully understood.

AREAS COVERED

The authors analyzed the recent evidence about the effects of vitamin D insufficiency on AD and the role of supplementation.

EXPERT OPINION

Both insufficient (25-49.9 ng/ml) and deficient levels (<25 ng/ml) of vitamin D may contribute to an increased susceptibility to AD. However, further well-designed prospective studies are needed for a better understanding of the involvement of low vitamin D concentrations in the AD natural history. Randomized clinical trials will also be necessary to address the issue of causality and determine whether vitamin D supplementation may be effective for the prevention or treatment of AD.

Low Vitamin D and Its Association with Cognitive Impairment and Dementia

Vitamin D is a neurosteroid hormone that regulates neurotransmitters and neurotrophins. It has anti-inflammatory, antioxidant, and neuroprotective properties. It increases neurotrophic factors such as nerve growth factor which further promotes brain health. Moreover, it is also helpful in the prevention of amyloid accumulation and promotes amyloid clearance. Emerging evidence suggests its role in the reduction of Alzheimer's disease hallmarks such as amyloid-beta and phosphorylated tau. Many preclinical studies have supported the hypothesis that vitamin D leads to attentional, behavioral problems and cognitive impairment. Cross-sectional studies have consistently found that vitamin D levels are significantly low in individuals with Alzheimer's disease and cognitive impairment compared to healthy adults. Longitudinal studies and meta-analysis have also exhibited an association of low vitamin D with cognitive impairment and Alzheimer's disease. Despite such evidence, the causal association cannot be sufficiently answered. In contrast to observational studies, findings from interventional studies have produced mixed results on the role of vitamin D supplementation in the prevention and treatment of cognitive impairment and dementia. The biggest issue of the existing RCTs is their small sample size, lack of consensus over the dose, and age of initiation of vitamin D supplements to prevent cognitive impairment. Therefore, there is a need for large double-blind randomized control trials to assess the benefits of vitamin D supplementation in the prevention and treatment of cognitive impairment.

Association between vitamin D deficiency and cognitive function in the elderly Korean population: A Korean frailty and aging cohort study

It is well known that vitamin D (VitD) plays an important role in bone and calcium metabolism in the human body. VitD has additional roles in the body including modulation of cell growth, neurogenesis, neuroprotection, detoxification, immune function, and reduction of inflammation. Recent studies reveal insufficiency of VitD as a risk factor for cognitive decline or dementia. VitD has a role in normal brain function; insufficiency of VitD may lead to decreased memory and cognitive function.Using 2 years of baseline data from Korean frailty and aging cohort study, 2990 subjects (1415 men and 1575 women) were recruited. A short form of Korean version of the consortium to establish a registry for Alzheimer disease (CERAD-K), an assessment of cognitive status in patients with dementia was used. Among CERAD-K tests, we included word list memory/recall/recognition, digit span (forward, backward), trail making test (TMT) A, and mini-mental state examination in the Korean version of the CERAD assessment packet (MMSE-KC). Serum samples were collected and 25-hydroxyvitamin D (25(OH)D) was measured. Serum 25(OH)D concentrations were classified into clinically relevant categories as: deficient (<10 nmol/L), insufficient (10-30 nmol/L), and sufficient (≥30 nmol/L).The mean age of participants was 76.5 ± 3.9 years, and 52.7% were women. Among 2990 participants, 119 (4.0%) were classified as 25(OH)D deficient and 2253 (75.3%) as insufficient. Only 618 (20.7%) participants were sufficient for 25(OH)D. Among them performance in MMSE-KC, TMT A, and digit span tests was better in sufficient, insufficient, and deficient groups, which was statistically significant (P < .05). However, in multivariable regression analysis after adjusting for age, sex, body mass index, education, center, seasonality, physical activity, and alcohol use, association between 25(OH)D and cognitive function was not statistically significant.Although, when comparing VitD levels, there were differences in cognitive tests among the groups, fully adjusted analysis did not show any association. This result suggests that cognition was not affected by VitD levels alone but also population and sociological variables. In a fully adjusted model, there was no statistically significant association between VitD and cognitive function in the elderly Koreans in logistic regression analysis.

Decreased Levels of Serum IGF-1 and Vitamin D Are Associated With Cognitive Impairment in Patients With Type 2 Diabetes

PURPOSE

To determine the association of serum insulin-like growth factor 1 (IGF-1) and vitamin D levels with cognition status in patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 173 patients with T2DM were recruited and divided into mild cognitive impairment (MCI) group (n = 94) and normal cognition (NC) group (n = 79). Levels of IGF-1 and 25(OH)D were measured and compared, and the correlations among IGF-1, 25(OH)D, and cognitive function were analyzed.

RESULTS

Insulin-like growth factor 1 and 25(OH)D levels significantly decreased in MCI group than those in the NC group (both P < .001). Multiple stepwise regression analysis revealed that IGF-1 (β = .146, P < .001) and 25(OH)D (β = .199, P < .001) independently predicted Montreal Cognitive Assessment (MoCA) scores. Partial least square regression showed that contributions of both 25(OH)D (P < .001) and IGF-1 (P < .001) to MoCA scores were significant, while no cross-effect was observed between them (P = .714).

CONCLUSIONS

Low serum IGF-1 and 25(OH)D levels may separately predict poor cognitive performance in patients with diabetes.

Longitudinal Changes in Muscle Mass and Strength, and Bone Mass in Older Adults: Gender-Specific Associations Between Muscle and Bone Losses

Background

The aims of this study were to investigate the longitudinal changes in muscle and bone with aging, and to clarify the muscle-bone relationships.

Methods

In a community-based prospective study, a total of 172 men and 165 women aged ≥ 65 years who had performed body composition analysis and bone mineral density (BMD) by dual-energy x-ray absorptiometry at baseline and 5-year follow-up evaluations were included.

Results

The rate of BMD loss in total hip was significantly associated with baseline legs lean mass and loss rate of leg strength, but not with the rate of muscle mass losses in men (r = .205 in leg lean mass, r = .170 in loss rate of leg muscle strength, p < .05 respectively). However, in women, it was significantly correlated with the rate of leg lean mass loss, but not with baseline values, and the rate of loss in leg muscle strength (r = .169 in the rate of loss in leg lean mass, r = .246 in the rate of loss in leg muscle strength, p < .05 respectively). In multivariate analyses, the rates of decrease in leg muscle strength showed independent positive associations with loss in total hip BMD in both men and women (β = 0.023 for men and β = 0.045 for women, both p < .05 respectively).

Conclusion

There was a gender difference in muscle and bone mass changes with aging, and muscle-bone interactions as well. However, a longitudinal change in muscle strength was the most significant independent factor associated with bone loss for both genders.

Effect of 2000 IU compared with 800 IU vitamin D on cognitive performance among adults age 60 years and older: a randomized controlled trial

BACKGROUND

Findings on the effects of vitamin D on cognitive performance have been inconsistent and no clinical trials with detailed cognitive testing in healthy older adults have been reported.

OBJECTIVES

We tested whether 2000 IU is superior to 800 IU vitamin D3/d for cognitive performance among relatively healthy older adults.

DESIGN

We analyzed data on cognitive performance as the secondary outcome of a 2-y double-blind randomized controlled trial that originally investigated the effect of vitamin D3 on knee function and pain in seniors with osteoarthritis. Participants were randomly assigned to either 2000 or 800 IU vitamin D3/d. Capsules had identical appearances and taste. A total of 273 community-dwelling older adults aged ≥60 y were enrolled 6-8 wk after unilateral joint replacement. Inclusion required a baseline Mini Mental State Examination (MMSE) score of 24. We implemented a detailed 2-h cognitive test battery. The primary cognitive endpoint was the score achieved in the MMSE. Secondary endpoints included a composite score of 7 executive function tests, auditory verbal and visual design learning tests, and reaction times.

RESULTS

At baseline, mean age was 70.3 y, 31.4% were vitamin D-deficient [25(OH)D <20 ng/mL], and mean ± SD MMSE score was 28.0 ± 1.5. Although the mean ± SD 25(OH)D concentrations achieved differed significantly between treatment groups at 24-mo follow-up (2000 IU = 45.1 ± 10.2 ng/mL; 800 IU = 37.5 ± 8.8 ng/mL; P < 0.0001), none of the primary or secondary endpoints of cognitive performance differed between treatment group. Results by treatment were similar for predefined subgroups of baseline 25(OH)D status (deficient compared with replete) and age (60-69 y compared with ≥70 y).

CONCLUSIONS

Our study does not support a superior cognitive benefit of 2000 IU compared with 800 IU vitamin D/d among relatively healthy older adults over a 24-mo treatment period. This trial was registered at clinicaltrials.gov as NCT00599807.

Serum 25(OH)D and Cognition: A Narrative Review of Current Evidence

The effect of low serum 25(OH)D on cognitive function is difficult to determine owing to the many factors that can influence these relationships (e.g., measurements, study design, and obesity). The primary purpose of this review was to synthesize the current evidence on the association between serum 25(OH)D and cognition giving special consideration to specific influential factors. A search was conducted in PubMed for studies published between 2010 and 2018 using terms related to serum 25(OH)D and cognition. Only studies that used liquid chromatography tandem-mass spectrometry (LC-MS) were included, since this is considered the 'gold standard method', to measure serum 25(OH)D. Of the 70 articles evaluated, 13 met all inclusion criteria for this review. The majority of the observational and longitudinal studies demonstrate a significant association between low serum 25(OH)D and compromised cognition. However, two randomized controlled trials showed inconsistent results on the impact of vitamin D supplementation on cognitive function. The varied methodologies for ascertaining cognition and the inclusion or exclusion of confounding variables (e.g., obesity, sunlight exposure) in the statistical analyses make drawing conclusions on the association between serum 25(OH)D and cognitive functioning inherently difficult. Despite the known higher occurrence of serum 25(OH) deficiency among minority populations, the majority of studies were conducted in with White participants. In order to more clearly discern the relationship between serum 25(OH)D and cognitive functioning, future studies should target more diverse study populations and utilize comprehensive measures to reliably capture cognition, as well as important known determinants of serum 25(OH)D.

Examining the relationship between nutrition and cerebral structural integrity in older adults without dementia

The proportion of adults aged 60 years and over is expected to increase over the coming decades. This ageing of the population represents an important health issue, given that marked reductions to cerebral macro- and microstructural integrity are apparent with increasing age. Reduced cerebral structural integrity in older adults appears to predict poorer cognitive performance, even in the absence of clinical disorders such as dementia. As such, it is becoming increasingly important to identify those factors predicting cerebral structural integrity, especially factors that are modifiable. One such factor is nutritional intake. While the literature is limited, data from available cross-sectional studies indicate that increased intake of nutrients such as B vitamins (for example, B6, B12 and folate), choline, n-3 fatty acids and vitamin D, or increased adherence to prudent whole diets (for example, the Mediterranean diet) predicts greater cerebral structural integrity in older adults. There is even greater scarcity of randomised clinical trials investigating the effects of nutritional supplementation on cerebral structure, though it appears that supplementation with B vitamins (B6, B12 and folic acid) or n-3 fatty acids (DHA or EPA) may be beneficial. The current review presents an overview of available research examining the relationship between key nutrients or adherence to select diets and cerebral structural integrity in dementia-free older adults.

Vitamin D in Neurological Diseases: A Rationale for a Pathogenic Impact

It is widely known that vitamin D receptors have been found in neurons and glial cells, and their highest expression is in the hippocampus, hypothalamus, thalamus and subcortical grey nuclei, and substantia nigra. Vitamin D helps the regulation of neurotrophin, neural differentiation, and maturation, through the control operation of growing factors synthesis (i.e., neural growth factor [NGF] and glial cell line-derived growth factor (GDNF), the trafficking of the septohippocampal pathway, and the control of the synthesis process of different neuromodulators (such as acetylcholine [Ach], dopamine [DA], and gamma-aminobutyric [GABA]). Based on these assumptions, we have written this review to summarize the potential role of vitamin D in neurological pathologies. This work could be titanic and the results might have been very fuzzy and even incoherent had we not conjectured to taper our first intentions and devoted our interests towards three mainstreams, demyelinating pathologies, vascular syndromes, and neurodegeneration. As a result of the lack of useful therapeutic options, apart from the disease-modifying strategies, the role of different risk factors should be investigated in neurology, as their correction may lead to the improvement of the cerebral conditions. We have explored the relationships between the gene-environmental influence and long-term vitamin D deficiency, as a risk factor for the development of different types of neurological disorders, along with the role and the rationale of therapeutic trials with vitamin D implementation.

The Role of Vitamin D in Brain Health: A Mini Literature Review

Vitamin D is vital for our body as it regulates calcium homeostasis and maintains bone integrity. In this article, we will discuss how vitamin D aids in the function of neuronal and glial tissue and the many health consequences in a person with vitamin D deficiency. Some of the effects of vitamin D deficiency that will be discussed include the development of dementia caused by the increase of cerebral soluble and insoluble amyloid-β (Aβ) peptides and a decrease of its anti-inflammatory/antioxidant properties, the link to depression by a reduction of the buffering of increased calcium in the brain, and vitamin D deficiency in expecting mothers linking to the development of autism and schizophrenic-like disorders, hypoxic brain injury, and other mental illnesses. Lastly, we will discuss how vitamin D deficiency is linked to the development of diabetes mellitus, its role in neuronal development and a decrease of microglial inflammatory function leading to increased brain infections.

Body mass index and vitamin D level in carpal tunnel syndrome patients

Background

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy of the upper extremity. The aim of this study is to evaluate the body mass index (BMI) and vitamin D levels in CTS patients.

Methods

The current study was conducted at Zagazig University Hospitals. It included 50 CTS patients and 50 controls. Clinical assessment was carried out to exclude symptoms and signs of neuropathy. Laboratory investigations including vitamin D levels, glycosylated hemoglobin, liver, and kidney function were carried out for every participant. All patients underwent electrodiagnostic study and completed Boston questionnaire to assess their pain sum score, symptom severity (SSS), and functional status (FSS).

Results

Patients had significantly higher BMI and lower vitamin D levels compared to controls (p = 0.003 and p = 0.001, respectively). Those with severe CTS had a significantly higher BMI and lower vitamin D levels than the others (p = 0.03 and p = 0.01 respectively). No significant difference was found between CTS subgroups regarding the SSS, while a higher significant FSS and pain sum score were reported in the severe CTS patients compared to the other two groups (p = 0.01 and p = 0.04 respectively). A significant negative correlation was detected between vitamin D levels and both of BMI, and Boston pain sum scores (p = 0.01 and p = 0.03 respectively). Also, an inverse correlation was detected between vitamin D levels and both of SSS and FSS (p = 0.14, p = 0.06). Furthermore, a significant positive and negative correlation between vitamin D levels and both of conduction velocity and distal motor latency respectively was observed (p = 0.02 and p = 0.01 respectively).

Conclusions

Carpal tunnel syndrome was significantly associated with hypovitaminosis D especially in patients with higher BMI. This highlights the importance of vitamin D supplements and weight loss regimes to minimize the severity of their pain.

Factors associated with dementia in elderly

We analyzed the factors associated with dementia in the elderly attended at a memory outpatient clinic of the University of Southern Santa Catarina (UNISUL). This is a cross-sectional study with data analysis of medical records from January 2013 to April 2016. The outcome was the clinical diagnosis of dementia. The control variables were: serum vitamin D level at the time of diagnosis, gender, skin color, schooling, age, type 2 diabetes, hypertension, and depression. We performed a crude and adjusted analysis with logistic regression. The sample consisted of 287 elderly, with the predominance of age between 60 and 69 years (48.78%), female (79.09%) and white (92.33%). The mean number of years of study was 6.95 years (SD ± 4.95) and mean vitamin D was 26.09 ng/mL (SD ± 9,20). The prevalence of elderly with dementia was 16.72%. Depression was the most prevalent (42.50%) among the morbidities, followed by hypertension (31.71%). The following were independently associated with dementia: vitamin D (OR = 0.92, 95%CI, 0.88;0.97), depression (OR = 4.09, 95%CI, 1.87;8.94), hypertension (OR = 2.65, 95%CI, 1.15;6.08) and individuals aged 80 years and over (OR = 3.97 95%CI, 1.59;9.91). Dementia prevalence was high and diagnosed dementia was associated with lower levels of vitamin D. Vitamin D is a modifiable factor, opening up essential perspectives for public health policies.

Cross-sectional associations of plasma vitamin D with cerebral β-amyloid in older adults at risk of dementia

BACKGROUND

Vitamin D deficiency is associated with an increased risk of Alzheimer's disease and increased beta-amyloid (Aβ) in animals. Hence we sought to investigate the relationship between plasma 25-hydroxyvitamin D (25(OH)D) and cerebral Aβ in older adults with subjective memory complaints.

METHODS

This is a secondary analysis of the Multidomain Alzheimer Preventive Trial. Participants were 178 dementia-free individuals aged 70 years or older with data on plasma 25(OH)D and cerebral Aβ load assessed by [18F]-florbetapir positron emission tomography. Plasma 25(OH)D was measured at study baseline using a commercially available electro-chemiluminescence competitive binding assay. Standard uptake value ratios (SUVRs) were generated using the cerebellum as a reference. Brain regions assessed included the cortex, anterior cingulate, anterior putamen, caudate, hippocampus, medial orbitofrontal cortex, occipital cortex, parietal cortex, pons, posterior cingulate, posterior putamen, precuneus, semioval centre and temporal cortex. Associations were explored using fully adjusted multiple linear regression models.

RESULTS

Participants had a mean (SD) age of 76.2 years (4.4) and 59.6% were female. The mean (SD) plasma 25(OH)D level was 22.4 ng/ml (10.8) and the mean (SD) cortical SUVR was 1.2 (0.2). We did not find any cross-sectional associations (p > 0.05) between baseline 25(OH)D levels and Aβ in any of the brain regions studied.

CONCLUSIONS

These preliminary results suggest that circulating 25(OH)D is not associated with cerebral Aβ in older adults. Further longitudinal studies with the measurement of mid-life vitamin D status are required to explore the relationship between vitamin D and Aβ accrual over time, thereby circumventing the shortfalls of a cross-sectional study.

Vitamin D Status and Intakes and Their Association With Cognitive Trajectory in a Longitudinal Study of Urban Adults

CONTEXT

Serum 25-hydroxyvitamin D [25(OH)D], and dietary and supplemental vitamin D may influence cognitive outcomes.

OBJECTIVES

Sex-, age-, and race-specific associations of vitamin D status and intake with longitudinal change in various cognitive domains were examined in a large sample of ethnically and socioeconomically diverse US urban adults.

DESIGN

Two prospective waves of data from the Healthy Aging in Neighborhoods of Diversity across the Life Span study were used.

PARTICIPANTS

Adults in Baltimore, Maryland, aged 30 to 64 years at baseline (n = 1231 to 1803), were followed for a mean (± standard deviation) of 4.64 ± 0.93 years. Visit 1 occurred between 2004 and 2009; visit 2, between 2009 and 2013; there were 1.5 to 2.0 visits per participant.

MAIN OUTCOME AND EXPOSURE MEASURES

Cognitive performance was assessed using 11 test scores covering domains of global cognition, attention, learning/memory, executive function, visuospatial/visuoconstruction ability, psychomotor speed, and language/verbal. Serum 25(OH)D, vitamin D intake, and use of supplements containing vitamin D were the key exposures.

RESULTS

A consistent relationship was found between vitamin D status (overall) and supplemental intake (older women and black adults), with a slower rate of decline in the domain of verbal fluency. Higher dietary intake of vitamin D was linked to slower rate of decline in verbal memory among younger women, and a slower rate of decline in visual memory/visuoconstructive abilities among white adults. All other associations were inconsistent.

CONCLUSIONS

Vitamin D status and intakes were inversely related to domain-specific cognitive decline in US urban adults.

Dementia and osteoporosis in a geriatric population: Is there a common link?

AIM

To determine the existence of a common pathological link between dementia and osteoporosis through reviewing the current evidence base.

METHODS

This paper reviews the current literature on osteoporosis and dementia in order to ascertain evidence of a common predisposing aetiology. A literature search of Ovid MED-LINE (1950 to June 2016) was conducted. The keywords “osteoporosis”, “osteoporotic fracture”, “dementia” and “Alzheimer’s disease” (AD) were used to determine the theoretical links with the most significant evidence base behind them. The key links were found to be vitamins D and K, calcium, thyroid disease, statins, alcohol and sex steroids. These subjects were then searched in combination with the previous terms and the resulting papers manually examined. Theoretical, in vitro and in vivo research were all used to inform this review which focuses on the most well developed theoretical common causes for dementia (predominantly Alzheimer’s type) and osteoporosis.

RESULTS

Dementia and osteoporosis are multifaceted disease processes with similar epidemiology and a marked increase in prevalence in elderly populations. The existence of a common link between the two has been suggested despite a lack of clear pathological overlap in our current understanding. Research to date has tended to be fragmented and relatively weak in nature with multiple confounding factors reflecting the difficulties of in vivo experimentation in the population of interest. Despite exploration of various possible mechanisms in search for a link between the two pathologies, this paper found that it is possible that these associations are coincidental due to the nature of the evidence available. One finding in this review is that prior investigation into common aetiologies has found raised amyloid beta peptide levels in osteoporotic bone tissue, with a hypothesis that amyloid beta disorders are systemic disorders resulting in differing tissue manifestations. However, our findings were that the most compelling evidence of a common yet independent aetiology lies in the APOE4 allele, which is a well-established risk for AD but also carries an independent association with fracture risk. The mechanism behind this is thought to be the reduced plasma vitamin K levels in individuals exhibiting the APOE4 allele which may be amplified by the nutritional deficiencies associated with dementia, which are known to include vitamins K and D. The vitamin theory postulates that malnutrition and reduced exposure to sunlight in patients with AD leads to vitamin deficiencies.

CONCLUSION

Robust evidence remains to be produced regarding potential links and regarding the exact aetiology of these diseases and remains relevant given the burden of dementia and osteoporosis in our ageing population. Future research into amyloid beta, APOE4 and vitamins K and D as the most promising aetiological links should be welcomed.

Associations of lower vitamin D concentrations with cognitive decline and long-term risk of dementia and Alzheimer's disease in older adults

INTRODUCTION

Hypovitaminosis D has been associated with several chronic conditions; yet, its association with cognitive decline and the risk of dementia and Alzheimer's disease (AD) has been inconsistent.

METHODS

The study population consisted of 916 participants from the Three-City Bordeaux cohort aged 65+, nondemented at baseline, with assessment of vitamin D status and who were followed for up to 12 years.

RESULTS

In multivariate analysis, compared with individuals with 25(OH)D sufficiency (n = 151), participants with 25(OH)D deficiency (n = 218) exhibited a faster cognitive decline. A total of 177 dementia cases (124 AD) occurred: 25(OH)D deficiency was associated with a nearly three-fold increased risk of AD (hazard ratio = 2.85, 95% confidence interval 1.37-5.97).

DISCUSSION

This large prospective study of French older adults suggests that maintaining adequate vitamin D status in older age could contribute to slow down cognitive decline and to delay or prevent the onset of dementia, especially of AD etiology.

Serum 25-hydroxyvitamin D deficiency and hepatic encephalopathy in chronic liver disease

AIM

To investigate the relationship between 25-hydroxyvitamin D (25-OHD) deficiency and hepatic encephalopathy (HE) in patients with chronic liver disease (CLD).

METHODS

A retrospective analysis of the results of 392 adult patients with chronic liver disease who were assessed for liver transplantation between 2006 and 2010 was undertaken. HE, severity of CLD, nutritional status and 25-OHD were analysed in patients assessed for liver transplantation between 2006 and 2010. Patients who presented with acute, fulminant or subacute disease, with a primary diagnosis of liver cancer, were assessed for re-transplantation or who did not have a 25-OHD measurement were excluded from the analysis.

RESULTS

One hundred and sixty-five patients were included in this analysis. The mean age of all patients was 53 ± 8 years. Moderate to severe 25-OHD deficiency was identified in 49 patients of whom 36 had grade 2-3 HE compared with 13 patients who were not encephalopathic (P ≤ 0.0001). Mild 25-OHD deficiency was not associated with HE. There was a significant correlation between the severity of 25-OHD deficiency and the severity of liver disease (r = 0.39, P ≤ 0.0001) and disease severity and the presence of HE (P ≤ 0.0001). Importantly, individuals with 25-OHD deficiency were more likely to have a diagnosis of overt HE (OHE) at a significantly lower model for end stage liver disease (MELD) score than individuals without OHE (P ≤ 0.0001). This significant difference was observed with MELD scores from 10 to 38.

CONCLUSION

25-OHD deficiency was observed in the majority of patients with CLD and for the first time was found to be significantly worse in patients with OHE.

Vitamin D is not associated with incident dementia or cognitive impairment: an 18-y follow-up study in community-living old men

Background: Vitamin D has been implicated as being important for maintaining cognitive function in old age. Results from longitudinal studies examining the association of vitamin D with incident dementia and cognitive impairment have been inconsistent.Objective: We investigated the relation between vitamin D, assessed in 3 different ways, and the risk of dementia.Design: We measured plasma 25-hydroxyvitamin D [25(OH)D] with the use of high-performance liquid chromatography-mass spectrometry, assessed dietary vitamin D intake with the use of 7-d dietary records, and created a vitamin D-synthesis genetic risk score (GRS) at baseline (1991-1995) in a cohort of 1182 Swedish men (mean age: 71 y). In a maximum of 18 y (median: 12 y) of follow-up, 116 men developed Alzheimer disease, 64 men developed vascular dementia, and 250 men developed all-cause dementia. An additional 80 men declined in cognitive function as assessed with the use of the Mini-Mental State Examination. Adjusted HRs and ORs were calculated with the use of Cox and logistic regressions.Results: The mean ± SD plasma 25(OH)D concentration was 68.7 ± 19.1 nmol/L. Plasma 25(OH)D, dietary vitamin D intake, and vitamin D-synthesis GRS were not associated with any cognitive outcomes (crude and adjusted HRs and ORs were ∼1.0 for all continuous exposures). The adjusted HR for all-cause dementia was 0.88 (95% CI: 0.59, 1.31) in men with plasma 25(OH)D concentrations ≤50 compared with >75 nmol/L. The adjusted HR for all-cause dementia was 0.92 (95% CI: 0.63, 1.32) for the lowest compared with highest tertiles of vitamin D intake. The adjusted HR for the continuous GRS for all-cause dementia was 1.04 (95% CI: 0.91, 1.19).Conclusion: In this cohort study, we show that there is no association between baseline vitamin D status and long-term risk of dementia or cognitive impairment over an 18-y period of time.

Vitamin D, Fibroblast Growth Factor 23 and Incident Cognitive Impairment: Findings from the REGARDS Study

Vitamin D protects against cognitive decline in animals but evidence in humans has been inconsistent. Fibroblast growth factor 23 (FGF23) is a hormone that inhibits vitamin D activation yet few studies examined whether FGF23 is associated with cognitive impairment. The objective of this study was to examine associations of 25(OH)D and FGF23 with incident cognitive impairment in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a cohort of black and white adults ≥45 years old. FGF23 and 25(OH)D were measured in 474 incident impairment cases and 561 controls. In multivariable-adjusted models, there were no significant associations of FGF23 with incident cognitive impairment. In analyses using clinically-relevant categories of 25(OH)D (< 20 ng/ml, 20–29.9 ng/ml, ≥30 ng/ml), there was no statistically significant association of lower 25(OH)D concentrations with odds of incident cognitive impairment in models adjusted for demographic, clinical, and laboratory variables and season of blood draw (tertile 1 [≥30 ng/ml] reference; tertile 2 [20–29.9 ng/ml], odds ratio [OR] 0.96, 95%CI 0.67, 1.38; tertile 3 [<20 ng/ml] OR 1.26, 95%CI 0.83, 1.91). When 25(OH)D was modeled as race-specific tertiles, there were no significant associations of 25(OH)D with incident cognitive impairment in whites, whereas lower 25(OH)D was associated with higher odds in blacks (tertile 1 [>23 ng/ml] reference; tertile 2 [15–23 ng/ml], OR 2.96, 95%CI 1.48,5.94; tertile 3 [<15 ng/ml] OR 2.40, 95%CI 1.07,5.40) in the fully adjusted model. In this cohort of older adults, lower race-specific tertiles of 25(OH)D were associated with higher incidence of cognitive impairment in black individuals but not white individuals. These data suggest that treating low 25(OH)D may be a novel strategy for addressing racial disparities in neurocognitive outcomes.

Evaluation of vitamin D levels in women with carpal tunnel syndrome

Studies suggest that vitamin D has a role in neuroprotection. We investigated whether vitamin D status is associated with carpal tunnel syndrome. Vitamin D levels were compared between carpal tunnel syndrome women (n = 135) and healthy control women (n = 135) or patients with other upper limb conditions (n = 135). There were no differences in vitamin D levels between the patients with carpal tunnel syndrome and the controls. However, women with carpal tunnel syndrome younger than 50 years old had significantly lower vitamin D levels than age-matched healthy control women (P = 0.023) or patients with other upper limb conditions (P = 0.035). When women with carpal tunnel syndrome and healthy control women were pooled, the incidence of carpal tunnel syndrome was higher in vitamin D deficient women than in non-deficient women, especially in those younger than 50 years. This study suggests a potential link between vitamin D status and the occurrence of carpal tunnel syndrome in women younger than 50 years but causation is not established.

TYPE OF STUDY/LEVEL OF EVIDENCE

Prognostic Level III.

Endocrine Risk Factors for Cognitive Impairment

Cognitive impairment, including Alzheimer's disease and other kinds of dementia, is a major health problem in older adults worldwide. Although numerous investigators have attempted to develop effective treatment modalities or drugs, there is no reasonably efficacious strategy for preventing or recovering from cognitive impairment. Therefore, modifiable risk factors for cognitive impairment have received attention, and the growing literature of metabolic risk factors for cognitive impairment has expanded from epidemiology to molecular pathogenesis and therapeutic management. This review focuses on the epidemiological evidence for the association between cognitive impairment and several endocrine risk factors, including insulin resistance, dyslipidemia, thyroid dysfunction, vitamin D deficiency, and subclinical atherosclerosis. Researches suggesting possible mechanisms for this association are reviewed. The research investigating modifiable endocrine risk factors for cognitive impairment provides clues for understanding the pathogenesis of cognitive impairment and developing novel treatment modalities. However, so far, interventional studies investigating the beneficial effect of the "modification" of these "modifiable risk factors" on cognitive impairment have reported variable results. Therefore, well-designed, randomized prospective interventional studies are needed.

Analysis of 25-Hydroxyvitamin D Status According to Age, Gender, and Seasonal Variation

BACKGROUND

The effects of age, gender, and seasonal variation on human levels of 25-hydroxyvitamin D (25(OH)D) are not well understood. In this study, we aimed to investigate 25(OH)D status according to these factors in a Korean population.

METHODS

A total of 303,943 serum 25(OH)D levels were measured using an electrochemiluminescence immunoassay between October 2011 and May 2014. Potential participants were ineligible for the study if they had significant renal, hepatic, or thyroid dysfunction, as well as any major ongoing disease that could influence serum 25(OH)D levels.

RESULTS

A total of 95,137 subjects (49,662 men and 45,475 women) were included in this study. The mean 25(OH)D levels were higher in men (42.4 nmol/l) than in women (32.9 nmol/l, P < 0.001). Among the men and women, 73.0% and 88.9%, respectively, had 25(OH)D levels <50 nmol/l, whereas only 3.8% of men and 1.4% of women had levels >75 nmol/l. The highest mean 25(OH)D value was noted in individuals aged ≥70 for both genders. The proportion of those with 25(OH)D levels <50 nmol/l appeared to be higher among younger subjects (P < 0.001). Lastly, there were significant differences between 25(OH)D levels in individuals during summer to fall and winter to spring in both genders, indicating seasonal periodicity (P < 0.001).

CONCLUSIONS

Serum 25(OH)D status varied according to gender, age, and season. Therefore, analyses of vitamin D status require individualized gender, age, and seasonally adjusted thresholds. Clinicians should consider these factors when determining optimal serum 25(OH)D levels in clinical practice.

Slowing the progression of Alzheimer's disease; what works?

Alzheimer's disease (AD) is an age-related progressive dementia, which is increasing in prevalence world-wide. Typically affecting short-term memory at onset, this devastating illness advances to impair all aspects of cognition, as well as non-cognitive domains. Although much effort has been made in recent years to develop disease-modifying treatments, medications which provided promising results in pre-clinical research have so far faltered in human clinical trials. Attention has recently shifted into trying to identify preventative measures that may delay the onset of the illness. Preventative factors include physical activity, proper diet, cognitive stimulation and the management of conditions such as hypertension, diabetes and obesity. However, it remains imperative to identify approaches that may help patients already diagnosed with the illness. Alongside pharmacological research, much work has been done on uncovering strategies which may slow down the progression of AD. This review aims to summarize evidence supporting or refuting methods impacting on the progression of the disease. AD remains a chronic and serious condition, therefore any intervention delaying the onset of moderate/severe symptoms will have a significant impact on patients and their families.

Vitamin D and Alzheimer's Disease: Neurocognition to Therapeutics

Alzheimer's disease (AD), the major cause of dementia worldwide, is characterized by progressive loss of memory and cognition. The sporadic form of AD accounts for nearly 90% of the patients developing this disease. The last century has witnessed significant research to identify various mechanisms and risk factors contributing to the complex etiopathogenesis of AD by analyzing postmortem AD brains and experimenting with animal and cell culture based models. However, the treatment strategies, as of now, are only symptomatic. Accumulating evidences suggested a significant association between vitamin D deficiency, dementia, and AD. This review encompasses the beneficial role of vitamin D in neurocognition and optimal brain health along with epidemiological evidence of the high prevalence of hypovitaminosis D among aged and AD population. Moreover, disrupted signaling, altered utilization of vitamin D, and polymorphisms of several related genes including vitamin D receptor (VDR) also predispose to AD or AD-like neurodegeneration. This review explores the relationship between this gene-environmental influence and long term vitamin D deficiency as a risk factor for development of sporadic AD along with the role and rationale of therapeutic trials with vitamin D. It is, therefore, urgently warranted to further establish the role of this potentially neuroprotective vitamin in preventing and halting progressive neurodegeneration in AD patients.