Evaluation of cognitive subdomains, 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D in the European Male Ageing Study

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.

Vitamin D status and cognitive performance in community-dwelling adults: A dose-response meta-analysis of observational studies

Low vitamin D status is linked with poorer cognition in adults while findings in relation to high levels are mixed.We performed a systematic review and meta-analyses to examine dose-response associations between 25-hydroxyvitamin D (25OHD) levelsand cognitive performance in community-dwelling adults. Thirty-eight observational studies were included in dose-response meta-analyses. Positive, nonlinear associations were identified between baseline25OHD levels and global cognition incross-sectional and longitudinal analyses, and for performance in memory and executive function in longitudinal analyses. When restricted to studies involving older adults, thepattern emerged forspecific domains in cross-sectional analyses. Poorer performance was associated with low 25OHD levels, while a sharp improvement was associated withlevels up to 60-70 nM/L. Further improvement was observed only for longitudinal global cognition. Our findings support the association between low vitamin D and poorer cognition and suggest levels of at least 60 nM/L are associated with better cognition during ageing.

The Vitamin D Receptor as a Potential Target for the Treatment of Age-Related Neurodegenerative Diseases Such as Alzheimer's and Parkinson's Diseases: A Narrative Review

The vitamin D receptor (VDR) belongs to the nuclear receptor superfamily of transcription factors. The VDR is expressed in diverse brain regions and has been implicated in the neuroprotective, antiaging, prosurvival, and anti-inflammatory action of vitamin D. Accordingly, a relationship between vitamin D insufficiency and susceptibility to neurodegenerative diseases has been suggested. However, due to the multitargeted mechanisms of vitamin D and its often overlapping genomic and nongenomic effects, the role of the VDR in brain pathologies remains obscure. In this narrative review, we present progress in deciphering the molecular mechanism of nuclear VDR-mediated vitamin D effects on prosurvival and anti-inflammatory signaling pathway activity within the central nervous system. In line with the concept of the neurovascular unit in pathomechanisms of neurodegenerative diseases, a discussion of the role of the VDR in regulating the immune and vascular brain systems is also included. Next, we discuss the results of preclinical and clinical studies evaluating the significance of vitamin D status and the efficacy of vitamin D supplementation in the treatment of Parkinson's and Alzheimer's diseases, emphasizing the possible role of the VDR in these phenomena. Finally, the associations of some VDR polymorphisms with higher risks and severity of these neurodegenerative disorders are briefly summarized.

Association between vitamin D concentration and delirium in hospitalized patients: A meta-analysis

BACKGROUND

Now the occurrence of delirium is more concerning to clinicians and psychiatrists. It has been reported that vitamin D deficiency may be a relevant factor in the development of delirium in hospitalized patients.

STUDY OBJECTIVE

To investigate the association between vitamin D concentration and delirium in hospitalized patients.

DESIGN

Meta-analysis.

METHODS

A systematic literature search was conducted using PubMed, EMBASE, and the Cochrane Library. The primary outcome was the occurrence of delirium in the inpatient setting. Odds ratios (OR) were calculated with random or fixed effects models.

RESULTS

In this article, we define the normal range of vitamin D concentrations as greater than 75 nmol / L, 50-75 nmol / L as vitamin D insufficiency, 25-50 nmol / L as vitamin D deficiency, and less than 25 nmol / L as vitamin D severe deficiency. The Results showed that severe vitamin D deficiency (OR: 1.98 [1.41-2.79], P<0.001) and vitamin D deficiency (OR: 1.50 [1.12-2.00], P = 0.006) were more likely to develop delirium than normal vitamin D levels. Subgroup analysis also revealed that low vitamin D concentrations were associated with a higher incidence of delirium, whether the cutoff point was 25 nmol/L (OR: 1.52 [1.40-1.64], P<0.001), 50 nmol/L (OR: 1.47 [1.19-1.82], P<0.001), or 75 nmol/L (OR: 1.54 [1.21-1.96], P<0.001). The included studies scored medium and high on the Newcastle-Ottawa quality assessment scale.

CONCLUSION

Compared with normal vitamin D levels, severe vitamin D deficiency and vitamin D deficiency, but not vitamin D insufficiency, are associated with a higher incidence of delirium in hospitalized patients.

TRIAL REGISTRATION

This review was registered in the PROSPERO database under identifier CRD42021271347. https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021271347.

Correlation between vitamin D and cognitive function in patients with traumatic brain injury in China

OBJECTIVE

This study investigated changes in vitamin D levels in traumatic brain injury (TBI) patients and the relationship between vitamin D levels and cognitive function.

METHODS

Thirty-five TBI patients in our hospital were randomly selected, and baseline data were collected. 25-Hydroxyvitamin D (25(OH)D) plasma levels were determined within a month of hospitalization, and awareness and cognitive function were assessed using the Glasgow Coma Scale (GCS) and the Mini Mental State Examination (MMSE), respectively, on the day of blood collection. The data were statistically analyzed.

RESULTS

The MMSE and GCS scores were positively correlated (p < 0.05); higher MMSE scores were associated with higher GCS scores. Moreover, the total score was positively correlated with directional ability, memory, and attention, suggesting high internal consistency of the MMSE score, but no significant correlation with other indicators was observed. 25(OH)D was positively correlated with the injury site (p < 0.05), suggesting that frontal damage has a significant impact on the plasma level of 25(OH)D.

CONCLUSION

The plasma vitamin D level in TBI patients may indicate frontal lobe damage. The overall plasma level of 25(OH)D in TBI patients was not significantly correlated with cognitive function, but the incidence of cognitive impairment was higher with 25(OH)D level between 10 and 30 ng/ml.

Mediation Effects of IL-1β and IL-18 on the Association Between Vitamin D Levels and Mild Cognitive Impairment Among Chinese Older Adults: A Case–Control Study in Taiyuan, China

Objective

Mild cognitive impairment (MCI) is a common, chronic, and complex disease in the elderly, which is often influenced by a variety of factors that include nutrition and inflammation. This study was undertaken to evaluate the mediation effects of inflammation on the association between vitamin D levels and MCI.

Methods

We explored the associations of inflammation and cognitive impairment related to 25(OH)D₃ deficiency among 360 older people from the communities in China. Demographic characteristics, lifestyle, and health status were investigated by questionnaire, cognitive function was detected by MoCA, and plasma 25(OH)D₃, interleukin-1β (IL-1β), and interleukin-18 (IL-18) were measured by ELISA. Spearman’s correlation analysis and logistic regression analysis were used to analyze the relationship among 25(OH)D₃, IL-1β, and IL-18 in the MCI group and the control group and further to analyze the relationship between 25(OH)D₃ and inflammatory factors in the MCI group. Finally, mediation analysis was performed to evaluate whether inflammation mediated the effect of 25(OH)D₃ deficiency on cognitive impairment.

Results

There were lower plasma 25(OH)D₃ concentration and higher IL-1β and IL-18 levels in the MCI group compared with the controls. The levels of 25(OH)D₃ were positively correlated with the MoCA scores and scores of different domains; the levels of IL-1β and IL-18 were negatively correlated with them (p < 0.05). In multivariate logistic analysis, there were significant associations among 25(OH)D₃, IL-1β, IL-18, and MCI after adjusted. Further analysis revealed the significant association between the subjects with VD deficiency and the highest quartile of IL-18 in MCI (OR = 4.066), not with IL-1β after adjusting the confounding variables in MCI group. Ultimately, mediation analysis suggested that IL-1β and IL-18 could explain 25.4 and 17.5% of effect of the risk of cognitive impairment related to 25(OH)D₃ deficiency.

Conclusion

Our findings suggested that 25(OH)D₃ deficiency could increase the risk of cognitive impairment by a mechanism partly involving inflammation. Therefore, vitamin D supplementation may improve or delay the decline in cognitive function caused by inflammation in the elderly.

Predicting Age From Behavioral Test Performance for Screening Early Onset of Cognitive Decline

Background: Neuronal reactions and cognitive processes slow down during aging. The onset, rate, and extent of changes vary considerably from individual to individual. Assessing the changes throughout the lifespan is a challenging task. No existing test covers all domains, and batteries of tests are administered. The best strategy is to study each functional domain separately by applying different behavioral tasks whereby the tests reflect the conceptual structure of cognition. Such an approach has limitations that are described in the article. Objective: Our aim was to improve the diagnosis of early cognitive decline. We estimated the onset of cognitive decline in a healthy population, using behavioral tests, and predicted the age group of an individual. The comparison between the predicted ("cognitive") and chronological age will contribute to the early diagnosis of accelerated aging. Materials and Methods: We used publicly available datasets (POBA, SSCT) and Pearson correlation coefficients to assess the relationship between age and tests results, Kruskal-Wallis test to compare distribution, clustering methods to find an onset of cognitive decline, feature selection to enhance performance of the clustering algorithms, and classification methods to predict an age group from cognitive tests results. Results: The major results of the psychophysiological tests followed a U-shape function across the lifespan, which reflected the known inverted function of white matter volume changes. Optimal values were observed in those aged over 35 years, with a period of stability and accelerated decline after 55-60 years of age. The shape of the age-related variance of the performance of major cognitive tests was linear, which followed the trend of lifespan gray matter volume changes starting from adolescence. There was no significant sex difference in lifelong dynamics of major tests estimates. The performance of the classification model for identifying subject age groups was high. Conclusions: ML models can be designed and utilized as computer-aided detectors of neurocognitive decline. Our study demonstrated great promise for the utility of classification models to predict age-related changes. These findings encourage further explorations combining several tests from the cognitive and psychophysiological test battery to derive the most reliable set of tests toward the development of a highly-accurate ML model.

Association of hsCRP and vitamin D levels with mild cognitive impairment in elderly type 2 diabetic patients

AIMS

The aim of the study was to determine the serum levels of 25-hydroxyvitamin D and high-sensitivity C-reactive protein (hsCRP) in elderly diabetic patients with and without mild cognitive impairment (MCI) and to examine factors (including 25-hydroxyvitamin D and hsCRP) associated with MCI in elderly patients with type 2 diabetes (T2DM).

METHODS

A total of 194 T2DM elders were evaluated: 62 subjects with MCI and 132 controls. Data was collected concerning biochemical parameters and biomarkers.

RESULTS

HsCRP concentration was elevated and 25-hydroxyvitamin D level was decreased in MCI patients to controls. HsCRP level was negatively correlated with 25-hydroxyvitamin D level and with MoCA score, and highly correlated with HbA1c level. The multivariable analysis indicated that less years of formal education, previous CVD and hypertension, increased number of co-morbidities, higher level of hsCRP and lower level of 25-hydroxyvitamin D, are the predisposing factors for MCI.

CONCLUSIONS

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.

Vitamin D status, cognitive decline and incident dementia: the Canadian Study of Health and Aging

OBJECTIVE

Vitamin D could prevent cognitive decline because of its neuroprotective, anti-inflammatory and antioxidant properties. This study aimed to evaluate the associations of plasma 25-hydroxyvitamin D (25(OH)D) concentrations with global cognitive function and incident dementia, including Alzheimer's disease (AD).

METHODS

The Canadian Study of Health and Aging is a 10-year cohort study of a representative sample of individuals aged 65 years or older. A total of 661 subjects initially without dementia with frozen blood samples and follow-up data were included. Global cognitive function was measured using the validated Modified Mini-Mental State (3MS) examination. A consensus diagnosis of all-cause dementia and AD was made between the physician and the neuropsychologist according to published criteria. Cognitive decline for a 5-year increase in age at specific 25(OH)D concentrations was obtained using linear mixed models with repeated measures. Hazard ratios of incident dementia and AD were obtained using semi-parametric proportional hazards models with age as time scale.

RESULTS

Over a mean follow-up of 5.4 years, 141 subjects developed dementia of which 100 were AD. Overall, no significant association was found between 25(OH)D and cognitive decline, dementia or AD. Higher 25(OH)D concentrations were associated with an increased risk of dementia and AD in women, but not in men.

CONCLUSION

This study does not support a protective effect of vitamin D status on cognitive function. Further research is needed to clarify the relation by sex.

Genetic, environmental and biomarker considerations delineating the regulatory effects of vitamin D on central nervous system function

Studies show that vitamin D (vit-D) (25(OH)D), the bioactive metabolite (1,25(OH)2D3) and vit-D receptors (vit-D receptor; protein disulphide isomerase, family A member 3) are expressed throughout the brain, particularly in regions pivotal to learning and memory. This has led to the paradigm that avoiding vit-D deficiency is important to preserve cognitive function. However, presently, it is not clear if the common clinical measure of serum 25(OH)D serves as a robust surrogate marker for central nervous system (CNS) homeostasis or function. Indeed, recent studies report CNS biosynthesis of endogenous 25(OH)D, the CNS expression of the CYP group of enzymes which catalyse conversion to 1,25(OH)2D3 and thereafter, deactivation. Moreover, in the periphery, there is significant ethnic/genetic heterogeneity in vit-D conversion to 1,25(OH)2D3 and there is a paucity of studies which have actually investigated vit-D kinetics across the cerebrovasculature. Compared with peripheral organs, the CNS also has differential expression of receptors that trigger cellular response to 1,25(OH)2D3 metabolites. To holistically consider the putative association of peripheral (blood) abundance of 25(OH)D on cognitive function, herein, we have reviewed population and genetic studies, pre-clinical and clinical intervention studies and moreover have considered potential confounders of vit-D analysis.

Serum Vitamin D Concentrations and Cognitive Change Over 20 Years: The Atherosclerosis Risk in Communities Neurocognitive Study

BACKGROUND/AIMS

25-hydroxyvitamin D (25[OH]D) concentrations have been associated with cognitive decline and incident dementia in elderly populations; however, these relationships are susceptible to reverse causation. Less is known about the association of midlife 25(OH)D with long-term cognitive decline.

METHODS

This was a prospective cohort study of 13,044 participants (mean age 57 years at baseline) in the Atherosclerosis Risk in Communities Study. 25(OH)D was measured from serum collected at baseline (1990-1992) using liquid chromatography tandem high-sensitivity mass spectrometry. Cognition was assessed using 3 neuropsychological tests at 3 time points, which were combined into a composite cognitive Z-score. Multivariable-adjusted linear mixed-effects models with random intercepts and slopes were used to estimate associations between 25(OH)D and cognitive change over 20 years.

RESULTS

Compared to persons with sufficient 25(OH)D (≥30 ng/mL), those with deficient (< 20 ng/mL) and intermediate (20-< 30 ng/mL) 25(OH)D concentrations had similar cognitive decline in composite cognitive Z-scores (deficient versus sufficient: -0.035 [95% CI -0.104 to 0.033] and intermediate versus sufficient: -0.029 [95% CI -0.080 to 0.023]).

CONCLUSIONS

Lower concentrations of 25(OH)D measured in midlife were not significantly associated with more rapid cognitive decline over a 20-year follow-up period. The results of this prospective study are less susceptible to reverse causation than prior studies.

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.

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.