Vitamin C Supplementation, APOE4 Genotype and Cognitive Functioning in a Rural-Dwelling Cohort

Low Plasma Ergothioneine Predicts Cognitive and Functional Decline in an Elderly Cohort Attending Memory Clinics

Low blood concentrations of the diet-derived compound ergothioneine (ET) have been associated with cognitive impairment and cerebrovascular disease (CeVD) in cross-sectional studies, but it is unclear whether ET levels can predict subsequent cognitive and functional decline. Here, we examined the temporal relationships between plasma ET status and cognition in a cohort of 470 elderly subjects attending memory clinics in Singapore. All participants underwent baseline plasma ET measurements as well as neuroimaging for CeVD and brain atrophy. Neuropsychological tests of cognition and function were assessed at baseline and follow-up visits for up to five years. Lower plasma ET levels were associated with poorer baseline cognitive performance and faster rates of decline in function as well as in multiple cognitive domains including memory, executive function, attention, visuomotor speed, and language. In subgroup analyses, the longitudinal associations were found only in non-demented individuals. Mediation analyses showed that the effects of ET on cognition seemed to be largely explainable by severity of concomitant CeVD, specifically white matter hyperintensities, and brain atrophy. Our findings support further assessment of plasma ET as a prognostic biomarker for accelerated cognitive and functional decline in pre-dementia and suggest possible therapeutic and preventative measures.

Rural-urban differences in food insecurity and associated cognitive impairment among older adults: findings from a nationally representative survey

Introduction

Due to rapid urbanization, Covid-19 pandemic and increasing food prices, a higher rate of food insecurity has been observed in recent years in India. Thus, we aim to study the prevalence of food insecurity among older Indian adults and the association of food insecurity as a modifiable risk factor with late-life cognitive impairment.

Method

Data for this study were obtained from the recent release of the Longitudinal Ageing Study in India (2017–18). The total sample size for the study was 31,464 older adults aged 60 years and above. Cognitive functioning was measured through five broad domains (memory, orientation, arithmetic function, executive function, and object naming) adapted from the cognitive module of the US Health and Retirement Study (HRS). Descriptive statistics along with cross-tabulation were presented in the study. Additionally, multivariable logistic regression analysis was used to fulfil the objectives of the study.

Results

It was found that 7.7% of older adults in rural areas reduced their size of meals due to unavailability (urban, 3.2%), 41.2% of them did not eat enough food of their choice (urban, 38.3%), 6.9% were hungry but did not eat food (urban, 2.6%), 5.0% did not eat for whole day (urban, 2.2%), and 6.9% lost weight due to lack of food in their household (urban, 2.9%). It was found that older adults who did not have enough food of their choice had significantly higher odds [AOR: 1.24; CI: 1.14, 1.35] of suffering from cognitive impairment in reference to their counterparts. Similarly, the older adults who were hungry but did not eat were 30% [AOR: 1.30; CI: 1.02, 1.73] more likely to suffer from cognitive impairment in reference to their counterparts. Interaction model revealed that older adults who had food insecurity in rural areas had higher odds of cognitive impairment than older adults who had food insecurity in urban areas.

Conclusion

The findings of the study highlight that the food security status in older adults may bring about greater challenges due to their limited economic resources. Interventions focusing on food security may have unintended positive impacts on late-life mental wellbeing as the older age is associated with higher cognitive deficits.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-02984-x.

Effects of functional variants of vitamin C transporter genes on apolipoprotein E E4-associated risk of cognitive decline: The Nakajima study

Apolipoprotein E E4 (APOE4) is a risk factor for cognitive decline. A high blood vitamin C (VC) level reduces APOE4-associated risk of developing cognitive decline in women. In the present study, we aimed to examine the effects of functional variants of VC transporter genes expressed in the brain (SLC2A1, SLC2A3, and SLC23A2) on APOE4-associated risk of developing cognitive decline. This case–control study involved 393 Japanese subjects: 252 cognitively normal and 141 cognitively impaired individuals (87 mild cognitive impairment and 54 dementia). Database searches revealed that rs1279683 of SLC23A2, and rs710218 and rs841851 of SLC2A1 are functional variants that are significantly associated with the altered expression of the respective genes and genotyped as three single nucleotide variants (SNVs). When stratified by SNV genotype, we found a significant association between APOE4 and cognitive decline in minor allele carriers of rs1279683 (odds ratio [OR] 2.02, 95% CI, 1.05–3.87, p = 0.035) but not in the homozygote carriers of the major allele. Significant associations between APOE4 and cognitive decline were also observed in participants with major allele homozygotes of rs710218 (OR 2.35, 95% CI, 1.05–5.23, p = 0.037) and rs841851 (OR 3.2, 95% CI, 1.58–6.46, p = 0.0012), but not in minor allele carriers of the respective SNVs. In contrast, the three functional SNVs showed no significant effect on cognitive decline. Our results imply that functional SNVs of VC transporter genes can affect APOE4-associated risk of developing cognitive decline via altered VC levels in the brain.

The Contribution of Plasma and Brain Vitamin C on Age and Gender-Related Cognitive Differences: A Mini-Review of the Literature

There is increasing evidence that sex differences in the brain may contribute to gender-related behavioral differences, including cognitive function. Literature has revealed gender dimorphisms in cognitive function between males and females. Additionally, several risk factors associated with cognitive decline depend on chronological age. It is well recognized that the process of aging is associated with a decline in cognitive ability and brain function. Various explanations may account for these gender-related cognitive differences and age-associated cognitive changes. Recent investigations have highlighted the importance of vitamin C in maintaining brain health and its association with cognitive function in both cognitively intact and impaired cohorts. The present review explores previous literature that has evaluated differences in plasma/brain vitamin C between genders and during aging. It then assesses whether these age and gender-related differences may affect the relationship between plasma/brain vitamin C and cognition. The purpose of this review was to examine the evidence for a link between plasma/brain vitamin C and cognition and the impact of gender and age on this relationship. Epidemiological studies have frequently shown higher vitamin C plasma concentrations in women. Similarly, aging has been systematically associated with reductions in plasma vitamin C levels. A range of animal studies has demonstrated potential gender and age-related differences in vitamin C brain distribution and utilization. The reviewed literature suggests that gender differences in plasma and brain vitamin C may potentially contribute to differences in gender-associated cognitive ability, particularly while females are pre-menopausal. Additionally, we can propose that age-associated differences in plasma and brain vitamin C may be potentially linked to age-associated cognitive differences, with older cohorts appearing more vulnerable to experience declines in plasma vitamin C concentrations alongside compromised vitamin C brain regulation. This review encourages future investigations to take into account both gender and age when assessing the link between plasma vitamin C concentrations and cognitive function. Further large scale investigations are required to assess whether differences in cognitive function between genders and age groups may be causally attributed to plasma vitamin C status and brain distribution and utilization.

Vitamin C Status and Cognitive Function: A Systematic Review

Vitamin C plays a role in neuronal differentiation, maturation, myelin formation and modulation of the cholinergic, catecholinergic, and glutaminergic systems. This review evaluates the link between vitamin C status and cognitive performance, in both cognitively intact and impaired individuals. We searched the PUBMED, SCOPUS, SciSearch and the Cochrane Library from 1980 to January 2017, finding 50 studies, with randomised controlled trials (RCTs, n = 5), prospective (n = 24), cross-sectional (n = 17) and case-control (n = 4) studies. Of these, 36 studies were conducted in healthy participants and 14 on cognitively impaired individuals (including Alzheimer’s and dementia). Vitamin C status was measured using food frequency questionnaires or plasma vitamin C. Cognition was assessed using a variety of tests, mostly the Mini-Mental-State-Examination (MMSE). In summary, studies demonstrated higher mean vitamin C concentrations in the cognitively intact groups of participants compared to cognitively impaired groups. No correlation between vitamin C concentrations and MMSE cognitive function was apparent in the cognitively impaired individuals. The MMSE was not suitable to detect a variance in cognition in the healthy group. Analysis of the studies that used a variety of cognitive assessments in the cognitively intact was beyond the scope of this review; however, qualitative assessment revealed a potential association between plasma vitamin C concentrations and cognition. Due to a number of limitations in these studies, further research is needed, utilizing plasma vitamin C concentrations and sensitive cognitive assessments that are suitable for cognitively intact adults.