Impacts of Illiteracy on the Risk of Dementia: A Global Health Perspective

Population attributable fractions of modifiable risk factors for dementia: a systematic review and meta-analysis

BACKGROUND

More than 57 million people have dementia worldwide. Evidence indicates a change in dementia prevalence and incidence in high-income countries, which is likely to be due to improved life-course population health. Identifying key modifiable risk factors for dementia is essential for informing risk reduction and prevention strategies. We therefore aimed to estimate the population attributable fraction (PAF) for dementia associated with modifiable risk factors.

METHODS

In this systematic review and meta-analysis, we searched Embase, MEDLINE, and PsycINFO, via Ovid, from database inception up to June 29, 2023, for population-derived or community-based studies and reviews reporting a PAF value for one or more modifiable risk factor for later-life dementia (prevalent or incident dementia in people aged ≥60 years), with no restrictions on dementia subtype, the sex or baseline age of participants, or the period of study. Articles were independently screened for inclusion by four authors, with disagreements resolved through consensus. Data including unweighted and weighted PAF values (weighted to account for communality or overlap in risk) were independently extracted into a predefined template by two authors and checked by two other authors. When five or more unique studies investigated a given risk factor or combination of the same factors, random-effects meta-analyses were used to calculate a pooled PAF percentage estimate for the factor or combination of factors. The review protocol was registered on PROSPERO, CRD42022323429.

FINDINGS

4024 articles were identified, and 74 were included in our narrative synthesis. Overall, PAFs were reported for 61 modifiable risk factors, with sufficient data available for meta-analysis of 12 factors (n=48 studies). In meta-analyses, the highest pooled unweighted PAF values were estimated for low education (17·2% [95% CI 14·4-20·0], p<0·0001), hypertension (15·8% [14·7-17·1], p<0·0001), hearing loss (15·6% [10·3-20·9], p<0·0001), physical inactivity (15·2% [12·8-17·7], p<0·0001), and obesity (9·4% [7·3-11·7], p<0·0001). According to weighted PAF values, low education (9·3% [6·9-11·7], p<0·0001), physical inactivity (7·3% [3·9-11·2], p=0·0021), hearing loss (7·2% [5·2-9·7], p<0·0001), hypertension (7·1% [5·4-8·8], p<0·0001), and obesity (5·3% [3·2-7·4], p=0·0001) had the highest pooled estimates. When low education, midlife hypertension, midlife obesity, smoking, physical inactivity, depression, and diabetes were combined (Barnes and Yaffe seven-factor model; n=9 studies), the pooled unweighted and weighted PAF values were 55·0% (46·5-63·5; p<0·0001) and 32·0% (26·6-37·5; p<0·0001), respectively. The pooled PAF values for most individual risk factors were higher in low-income and middle-income countries (LMICs) versus high-income countries.

INTERPRETATION

Governments need to invest in a life-course approach to dementia prevention, including policies that enable quality education, health-promoting environments, and improved health. This investment is particularly important in LMICs, where the potential for prevention is high, but resources, infrastructure, budgets, and research focused on ageing and dementia are limited.

FUNDING

UK Research and Innovation (Medical Research Council).

Mitochondria Dysfunction and Neuroinflammation in Neurodegeneration: Who Comes First?

Neurodegenerative diseases (NDs) encompass an assorted array of disorders such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, each characterised by distinct clinical manifestations and underlying pathological mechanisms. While some cases have a genetic basis, many NDs occur sporadically. Despite their differences, these diseases commonly feature chronic neuroinflammation as a hallmark. Consensus has recently been reached on the possibility that mitochondria dysfunction and protein aggregation can mutually contribute to the activation of neuroinflammatory response and thus to the onset and progression of these disorders. In the present review, we discuss the contribution of mitochondria dysfunction and neuroinflammation to the aetiology and progression of NDs, highlighting the possibility that new potential therapeutic targets can be identified to tackle neurodegenerative processes and alleviate the progression of these pathologies.

Polysaccharide of Taxus chinensis var. mairei Cheng et L.K.Fu attenuates neurotoxicity and cognitive dysfunction in mice with Alzheimer's disease

CONTEXT

Polysaccharide of Taxus chinensis var. mairei Cheng et L.K.Fu (Taxaceae) (PTM) functions in anti-apoptosis and antioxidation, but its function on Alzheimer's disease (AD) remains unclear.

OBJECTIVE

To investigate the effect of PTM on AD.

MATERIALS AND METHODS

C57BL/6J mice were randomly divided into three groups: control, d-galactose (d-gal), and d-gal + PTM. AD-like symptom was induced by d-gal for 6 weeks, followed with PTM (0.4 g/kg/d) for 14 days. PTM was added to BV2 cells stimulated with d-gal (1, 10, 20, 50, 100 and 500 μg/mL). Cell viability was evaluated by MTT assay. The expression of NRF2, SOD, cleaved caspase-3, Bax and Bcl-2 were detected with Western blot analysis. Cognitive function was evaluated by Morris water maze test.

RESULTS

Decreased cleaved caspase-3 (1.30 ± 0.09) and Bax/Bcl2 ratio (1.32 ± 0.11) were observed in BV2 cells induced by d-gal + PTM (50 μg/mL). Increased MDA and ROS and decreased SOD were observed in d-gal group. However, decreased MDA (175 ± 9 ng/mL) and ROS level (188 ± 38 ng/mL) were observed after treated with PTM group (p < 0.05). In addition, the expression of NRF2 decreased in d-gal group (0.75 ± 0.09) but increased after treated with PTM (p < 0.05). Furthermore, decreased Aβ1-42 was observed and the cognitive function was improved after PTM intervention (p < 0.05).

CONCLUSIONS

This is the first report that PTM inhibited oxidative stress and apoptosis in AD. The result will further accelerate the applications of Taxus chinensis var. mairei and the treatment for AD.

Decline in the Incidence of All-Cause and Alzheimer's Disease Dementia: a 12-Year-Later Rural Cohort Study in Korea

BACKGROUND

There has been no study on the time trends of dementia incidence in Korea. We report the 5-year incidence and its correlates of all-cause and Alzheimer's disease (AD) dementia, and compared our results with those of a 12-year-prior cohort study conducted in the same area.

METHODS

A total of 751 community-dwelling older adults were followed up for a mean duration of 5.4 years. The age-, gender-, and educational attainment-specific incidence of all-cause and AD dementia were reported as cases per 1,000 person-years. We performed univariate and multivariate cox proportional hazard regression analyses to determine whether baseline sociodemographic, lifestyle, and clinical variables were associated with the risk of all-cause and AD dementia. A 12-year-prior cohort study was used for descriptive comparison to indicate the time trends of dementia incidence.

RESULTS

The incidence rates were 16.2 and 13.0 cases per 1,000 person-years for all-cause and AD dementia, respectively. The baseline diagnosis of mild cognitive impairment increased the 5-year incidence of all-cause dementia by more than 4-fold. Old age and low baseline global cognitive function were noted as risk factors for both all-cause and AD dementia.

CONCLUSION

Upon comparing the results with those from the earlier cohort study in Yeoncheon, the incidence of all-cause and AD dementia decreased by approximately 40% over 12 years; it has been mainly driven by the increase in the educational level of older adults. The declining time trends of incidence should be taken into account for estimating the future prevalence of dementia in Korea.

Validation study of the Alzheimer's Disease Assessment Scale-Cognitive Subscale for people with mild cognitive impairment and Alzheimer's disease in Chinese communities

OBJECTIVE

Our study aimed to verify the validity of the Chinese version of Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) for the community-dwelling older people in China.

METHODS

A total of 1276 individuals composed by 628 normal controls (NCs), 572 people living with mild cognitive impairment (MCI), and 76 people living with Alzheimer's disease (AD) were recruited for the current study. All of the participants underwent ADAS-Cog, clinical interview and examination, Quick Cognitive Screening Scale for the Elderly, and Activities of Daily Living Scale. The sensitivity and specificity of ADAS-Cog were calculated, and a receiver operating characteristic curve (ROC curve) was drawn to decide the optimal cutoff points of ADAS-Cog for screening MCI and AD.

RESULTS

Statistically significant differences were observed among the three groups (P <. 001, NC < MCI <AD), in terms of the total and subtask scores of ADAS-Cog. The optimal cutoff value for MCI was 10 points with an area under the curve (AUC) of 0.824, sensitivity of 61.4%, and specificity of 93.2%. Comparatively, the best cutoff value for AD was 15 points with an AUC of 0.905, sensitivity of 73.7%, and specificity of 92.4%. The overall accuracy was 70.5%, and the accuracy of diagnosing cognitively healthy older people, MCI patients, and AD patients was 81.7%, 58.0%, and 71.1%, respectively.

CONCLUSION

The present study illustrates that the Chinese version of the ADAS-Cog total score is able to detect cognitive impairment of AD patients in Chinese communities but has a lower efficacy for MCI.

The Role of Nutrition and Literacy on the Cognitive Functioning of Elderly Poor Individuals

Maintaining cognitive function is a prerequisite of living independently, which is a highly valued component in older individuals' well-being. In this article we assess the role of early-life and later-life nutritional status, education, and literacy on the cognitive functioning of older adults living in poverty in Peru. We exploit the baseline sample of the Peruvian noncontributory pension program Pension 65 and find that current nutritional status and literacy are strongly associated with cognitive functioning for poor older adults. In a context of rising popularity of noncontributory pension programs around the world, our study intends to contribute to the discussion of designing accompanying measures to the pension transfer, such as adult literacy programs and monitoring of adequate nutrition of older adults.