Digit symbol substitution test score and hyperhomocysteinemia in older adults

Homocysteine - A predictor for five year-mortality in patients with subjective cognitive decline, mild cognitive impairment and Alzheimer's dementia

BACKGROUND

Subjective Cognitive Decline (SCD) and Mild Cognitive Impairment (MCI) are preclinical stages of Alzheimer's Disease (AD), which is the most common entity of dementia. Homocysteine is an amino acid in the methionine cycle, and many studies revealed a significant association between elevated homocysteine serum levels and the progression of dementia. The primary objective of this retrospective study was to investigate whether elevated homocysteine serum levels could be associated with mortality and neuropsychological test results in individuals suffering from SCD, MCI or AD.

METHODS

This study is a single-center explorative retrospective data analysis with 976 data protocols from the Memory Outpatient's Clinic of the Medical University of Vienna included. All patients underwent a neurological examination, a laboratory blood test, and neuropsychological testing to establish a diagnosis of either SCD, MCI, or AD. Data was evaluated by Kaplan-Meier functions, factor analysis, and binary logistic regression models.

RESULTS

Patients with AD showed significantly higher mean homocysteine levels (SCD 12.15 ± 4.71, MCI 12.80 ± 4.81, AD 15.0 ± 6.44 μmol/L) compared to those with SCD and MCI (p ≤ .001). The mean age of patients with AD (75.2 ± 7.8) was significantly older at the time of testing than of patients with MCI (69.1 ± 9.6) or SCD (66.8 ± 9.3). Since homocysteine levels increase with age, this could be a possible explanation for the higher levels of AD patients. The age at death did not differ significantly between all diagnostic subgroups, resulting in the shortest survival times for AD patients. Homocysteine levels were negatively associated with in Mini-Mental State Examination (MMSE) and Neuropsyhcological Test Battery Vienna (NTBV) factors F1-F4 (F1 = attention, F2 = memory, F3 = executive functions, F4 = naming/verbal comprehension). Moreover, higher homocysteine levels significantly predicted shorter five-year survival in the logistic regression models, even after adjusting for age, diagnostic subgroups, sex, years of education and results of neuropsychological testing.

CONCLUSION

The results of this study suggest that homocysteine levels are independently associated with impaired cognitive function and increased five-year mortality.

A systematic review of existing peripheral biomarkers of cognitive aging: Is there enough evidence for biomarker proxies in behavioral modification interventions?: An initiative in association with the nutrition, exercise and lifestyle team of the Canadian Consortium on Neurodegeneration in Aging

Peripheral biomarkers have shown significant value in predicting brain health and may serve as a useful proxy measurement in the assessment of evidence-based lifestyle behavior modification programs, including physical activity and nutrition programs, that aim to maintain cognitive function in late life. The aim of this systematic review was to elucidate which peripheral biomarkers are robustly associated with cognitive function among relatively healthy non-demented older adults. Following the standards for systematic reviews (PICO, PRIMSA), and employing MEDLINE and Scopus search engines, 222 articles were included in the review. Based on the review of biomarker proxies of cognitive health, it is recommended that a comprehensive biomarker panel, or biomarker signature, be developed as a clinical end point for behavior modification trials aimed at enhancing cognitive function in late life. The biomarker signature should take a multisystemic approach, including lipid, immune/inflammatory, and metabolic biomarkers in the biological signature index of cognitive health.

B-Vitamin Therapy for Kidney Transplant Recipients Lowers Homocysteine and Improves Selective Cognitive Outcomes in the Randomized FAVORIT Ancillary Cognitive Trial

BACKGROUND

Objectives: Elevated plasma total homocysteine (tHcy) is associated with increased risk of cardiovascular disease, stroke and dementia. Results of clinical trials using B-vitamins to reduce the cognitive risks attributed to tHcy have been inconsistent. The high prevalence of both hyperhomocysteinemia and cognitive impairment among kidney transplant recipients makes them an important population in which to evaluate the effect of lowering homocysteine on cognitive function. We therefore evaluated whether B-vitamin therapy to lower tHcy would prevent cognitive-decline in a cohort of stable kidney transplant recipients.

DESIGN

The study was a longitudinal ancillary of the FAVORIT trial, a randomized, placebo-controlled multi-site trial of high-dose B vitamins to reduce cardiovascular and cerebrovascular events in clinically stable kidney transplant recipients with elevated tHcy.

PARTICIPANTS

584 participants from 18 sites across North America.

INTERVENTION

The intervention consisted of a daily multivitamin containing high-doses of folate (5.0 mg), vitamin B12 (1.0 mg) and vitamin B6 (50 mg). The placebo consisted of a daily multi-vitamin containing no folate and recommended daily allowances of vitamins B12 and B6 (0 mg folate; 2.0 µg vitamin B12; 1.4 mg vitamin B6).

MEASUREMENTS

Annual neuropsychological assessment for up to 5 years (mean 3.3 years) using a standardized test battery. Efficacy was analyzed on an intention-to-treat basis using end-of-trial data. Subgroup analyses included stratification for baseline plasma B-vitamin and tHcy concentrations.

RESULTS

At baseline, cognitive impairment was common with 61% of participants falling more than one standard deviation below published norms for at least one cognitive test. Fewer than 1% of participants had insufficient plasma folate < 5 ng/ml or vitamin B12 < 148 pmol/L. However, 44.6% had plasma B6 concentrations < 30 nmol/L. At follow-up, processing speed and memory scores were modestly but significantly better in the B-vitamin supplement group than in controls (p≤0.05). There was no interaction between baseline tHcy, B-vitamin status and treatment on the cognitive outcomes.

CONCLUSIONS

High-dose B-vitamin supplementation provided modest cognitive benefit for kidney transplant recipients with elevated baseline tHcy. Since nearly all participants were folate and vitamin B12 sufficient at baseline, the potential cognitive benefits of folate and B12 supplementation in individuals with poor B-vitamin status remains to be determined.

Plasma homocysteine and cerebral small vessel disease as possible mediators between kidney and cognitive functions in patients with diabetes mellitus

Cognitive impairment is more prevalent in those with decreased kidney function. We tested a hypothesis that an increased homocysteine and/or cerebral small vessel diseases (SVDs) mediate the link between kidney and cognitive functions in a cross-sectional study in 143 type 2 diabetes patients without diagnosis of dementia or prior stroke. The exposure and outcome variables were estimated glomerular filtration rate (eGFR) and cognitive performance evaluated with Modified Mini-Mental State (3 MS) examination, respectively. The candidate mediators were plasma homocysteine concentration, and SVDs including silent cerebral infarction, cerebral microbleed, periventricular hyperintensity, and deep and subcortical white matter hyperintensity by magnetic resonance imaging. In multiple regression models adjusted for 12 potential confounders, eGFR was positively associated with 3 MS score, inversely with homocysteine, but not significantly with the presence of any type of SVD. The association of eGFR with 3 MS remained significant when each of the SVDs was added to the model, whereas it disappeared when homocysteine was included in place of SVD. Mediation analysis indicated nearly significant mediation of homocysteine (P = 0.062) but no meaningful mediations of SVDs (P = 0.842-0.930). Thus, homocysteine, not SVDs, was shown to be the possible mediator between kidney and cognitive functions in patients with type 2 diabetes mellitus.