Prevalence of Dementia in China in 2015: A Nationwide Community-Based Study

Association between garden work and risk of incident dementia in an older population in China: a national cohort study

OBJECTIVES

Evidence on the association between garden work and risk of incident dementia in the older Chinese population is limited. This study aimed to explore the association between the frequency of garden work and risk of incident dementia in an older population in China.

STUDY DESIGN

This was a national cohort study.

METHODS

This study analysed data from 8676 participants (median age: 86 years) from the Chinese Longitudinal Healthy Longevity Survey. Cox proportional hazard models were used to assess the association between the frequency of garden work and risk of incident dementia using hazard ratios (HRs) and 95% confidence intervals (CIs). Multiplicative and additive interaction effects were calculated between the frequency of garden work and age, sex or residence on incident dementia; subgroup analyses of the association were also conducted by age, sex and residence. In addition, sensitivity analyses were performed to assess the robustness of the results.

RESULTS

During 4.31 years (median) of follow-up, 633 participants developed dementia. Compared with participants who did not engage in garden work, the adjusted risk of incident dementia for those who regularly or almost daily engaged in garden work decreased by 28% (HR = 0.72, 95% CI: 0.57-0.93). An additive interaction effect between frequency of garden work and age on incident dementia was observed, with subgroup analyses demonstrating similar statistically significant associations among participants aged ≥85 years, women and city or town residents. Sensitivity analyses were consistent with the primary analysis in the present study.

CONCLUSIONS

Frequent engagement in garden work may be associated with a reduced risk of dementia and may be an effective measure to prevent incident dementia in the older population in China.

The circadian syndrome is a predictor for cognition impairment in middle-aged adults: Comparison with the metabolic syndrome

AIMS

Circadian syndrome (CircS) is considered a better predictor for cardiovascular disease than the metabolic syndrome (MetS). We aim to examine the associations between CircS and MetS with cognition in Chinese adults.

METHOD

We used the data of 8546 Chinese adults aged ≥40 years from the 2011 China Health and Retirement Longitudinal Study. MetS was defined using harmonised criteria. CircS included the components of MetS plus short sleep and depression. The cut-off for CircS was set as ≥4. Global cognitive function was assessed during the face-to-face interview.

RESULTS

CircS and MetS had opposite associations with the global cognition score and self-reported poor memory. Compared with individuals without the CircS and MetS, the regression coefficients (95%CI) for global cognition score were -1.02 (-1.71 to -0.34) for CircS alone and 0.52 (0.09 to 0.96) for MetS alone in men; -1.36 (-2.00 to -0.72) for CircS alone and 0.60 (0.15 to 1.06) for MetS alone in women. Having CircS alone was 2.53 times more likely to report poor memory in men (95%CI 1.80-3.55) and 2.08 times more likely in women (95%CI 1.54-2.81). In contrast, having MetS alone was less likely to report poor memory (OR 0.64 (0.49-0.84) in men and 0.65 (0.52-0.81) in women). People with CircS and MetS combined were more likely to have self-reported poor memory.

CONCLUSIONS

CircS is a strong and better predictor for cognition impairment than MetS in Chinese middle-aged adults. MetS without short sleep and depression is associated with better cognition.

Temporal trends and disparities of population attributable fractions of modifiable risk factors for dementia in China: a time-series study of the China health and retirement longitudinal study (2011-2018)

Background

In China, dementia poses a significant public health challenge, exacerbated by an ageing population and lifestyle changes. This study assesses the temporal trends and disparities in the population-attributable fractions (PAFs) of modifiable risk factors (MRFs) for new-onset dementia from 2011 to 2018.

Methods

We used data from the China Health and Retirement Longitudinal Study (CHARLS), covering 75,214 person-waves. We calculated PAFs for 12 MRFs identified by the Lancet Commission (including six early-to mid-life factors and six late-life factors). We also determined the individual weighted PAFs (IW-PAFs) for each risk factor. Subgroup analyses were conducted by sex, socio-economic status (SES), and geographic location.

Findings

The overall PAF for dementia MRFs had a slight increase from 45.36% in 2011 to 52.46% in 2018, yet this change wasn't statistically significant. During 2011-2018, the most contributing modifiable risk was low education (average IW-PAF 11.3%), followed by depression, hypertension, smoking, and physical inactivity. Over the eight-year period, IW-PAFs for risk factors like low education, hypertension, hearing loss, smoking, and air pollution showed decreasing trends, while others increased, but none of these changes were statistically significant. Sex-specific analysis revealed higher IW-PAFs for traumatic brain injury (TBI), social isolation, and depression in women, and for alcohol and smoking in men. The decline in IW-PAF for men's hearing loss were significant. Lower-income individuals had higher overall MRF PAFs, largely due to later-life factors like depression. Early-life factors, such as TBI and low education, also contributed to SES disparities. Rural areas reported higher overall MRF PAFs, driven by factors like depression, low education, and hearing loss. The study also found that the gap in MRF PAFs across different SES groups or regions either remained constant or increased over the study period.

Interpretation

The study reveals a slight but non-significant increase in dementia's MRF PAF in China, underscoring the persistent relevance of these risk factors. The findings highlight the need for targeted public health strategies, considering the demographic and regional differences, to effectively tackle and reduce dementia risk in China's diverse population.

Funding

This work was supported by the PKU Young Scholarship in Global Health and Development.

Geographical variation in dementia prevalence across China: a geospatial analysis

Background

Dementia poses great health and social challenges in China. Dementia prevalence may vary across geographic areas, while comparable estimations on provincial level is lacking. This study aims to estimate dementia prevalence by provinces across China, taking into account risk factors of individual level and potential spatial correlation of provinces.

Methods

In this study, 17,176 adults aged 50 years or older were included from the fourth wave of the China Health and Retirement Longitudinal Study (CHARLS 2018), covering 28 provinces, autonomous regions and municipalities. To improve provincial representativeness, we constructed provincial survey weights based on China 7th census (2020). The prevalence of dementia and 95% Bayesian credible intervals (BCIs) were estimated using a Bayesian conditional autoregressive (CAR) model with spatially varying coefficients of covariates.

Findings

The weighted prevalence of dementia at provincial level in China in 2018 ranged from 2.62% (95%BCI: 1.70%, 3.91%) to 13.53% (95%BCI: 8.82%, 20.93%). High dementia prevalence was concentrated in North China, with a prominent high-high cluster, while provinces of low prevalence were concentrated on East and South China, characterized by a low-low cluster. Ordered by the median estimation of prevalence, the top 10% of provinces, include Xinjiang, Jilin, and Beijing. Meanwhile, Fujian, Zhejiang, and Guangdong rank among the last. The association between dementia prevalence and drinking, smoking, social isolation, physical inactivity, hearing impairment, hypertension, and diabetes exhibits provincial variation.

Interpretation

Our study identifies a geospatial disparity in dementia prevalence and risk factor effects across China's provinces, with high-high and low-low clusters in some northern and southern provinces, respectively. The findings emphasize the need for targeted strategies, such as addressing hypertension and hearing impairment, in specific regions for more effective dementia prevention and treatment.

Funding

National Science Foundation of China/the Economic and Social Research Council, UK Research and Innovation joint call: Understanding and Addressing Health and Social Challenges for Ageing in the UK and China. UK-China Health And Social Challenges Ageing Project (UKCHASCAP): present and future burden of dementia, and policy responses (grant number 72061137003, ES/T014377/1).

Long-term trends in Alzheimer's disease and other dementias deaths with high body mass index in China from 1990 to 2019, and projections up to 2042

BACKGROUND

In China, the rising prevalence of high Body Mass Index (BMI) is linked to increasing health issues, including Alzheimer's disease (AD). This study analyzes mortality trends related to AD and other dementias associated with high BMI from 1990 to 2019, considering age, period, and birth cohort effects, and forecasts future trends.

METHODS

We analyzed mortality data for AD and other dementias linked to high BMI in Chinese residents from the Global Burden of Disease 2019 database. Using Joinpoint regression, we examined age-standardized mortality rate (ASMR) trends and calculated annual and average annual percentage changes (APC and AAPC). Age-period-cohort models provided deeper insights, with Bayesian models used to project future ASMR trends to 2042.

RESULTS

From 1990 to 2019, the ASMR for AD and other dementias associated with high BMI in China showed an overall increasing trend. Females had a lower increase rate than males, yet their overall levels remained higher. Specifically, the ASMR for males increased by an average of 2.70% per year, peaking between 2006 and 2010, while for females, it increased by an average of 2.29% per year, also peaking in the same period. Age-period-cohort analysis revealed increasing mortality relative risk with age and period, but a decrease with birth cohort. Projections suggest a continued rise in ASMR by 2042, with rates for males and females expected to be 2.48/100,000 and 2.94/100,000, respectively.

CONCLUSION

The increasing mortality trend from AD and other dementias associated with high BMI highlights the urgent need for policy interventions focused on overweight prevention, particularly vital for addressing the health challenges in China's aging population.

High prevalence of subjective cognitive decline in older Chinese adults: a systematic review and meta-analysis

Background

Subjective cognitive decline (SCD) is considered a preclinical stage of Alzheimer's disease. However, reliable prevalence estimates of SCD in the Chinese population are lacking, underscoring the importance of such metrics for policymakers to formulate appropriate healthcare strategies.

Objective

To systematically evaluate SCD prevalence among older Chinese adults.

Methods

PubMed, Web of Science, The Cochrane Library, Embase, CNKI, Wanfang, VIP, CBM, and Airiti Library databases were searched for studies on SCD in older Chinese individuals published before May 2023. Two investigators independently screened the literature, extracted the information, and assessed the bias risk of the included studies. A meta-analysis was then conducted using Stata 16.0 software via a random-effects model to analyze SCD prevalence in older Chinese adults.

Results

A total of 17 studies were included (n = 31,782). The SCD prevalence in older Chinese adults was 46.4% (95% CI, 40.6-52.2%). Further, subgroup analyzes indicated that SCD prevalence was 50.8% in men and 58.9% among women. Additionally, SCD prevalence in individuals aged 60-69, 70-79, and ≥ 80 years was 38.0, 45.2, and 60.3%, respectively. Furthermore, SCD prevalence in older adults with BMI <18.5, 18.5-24.0, and > 24.0 was 59.3, 54.0, and 52.9%, respectively. Geographically, SCD prevalence among older Chinese individuals was 41.3% in North China and 50.0% in South China. In terms of residence, SCD prevalence was 47.1% in urban residents and 50.0% among rural residents. As for retired individuals, SCD prevalence was 44.2% in non-manual workers and 49.2% among manual workers. In the case of education, individuals with an education level of "elementary school and below" had an SCD prevalence rate of 62.8%; "middle school, "52.4%; "high school, "55.0%; and "college and above, "51.3%. Finally, SCD prevalence was lower among married individuals with surviving spouses than in single adults who were divorced, widowed, or unmarried.

Conclusion

Our systematic review and meta-analysis identified significant and widespread SCD prevalence in the older population in China. Therefore, our review findings highlight the urgent requirement for medical institutions and policymakers across all levels to prioritize and rapidly develop and implement comprehensive preventive and therapeutic strategies for SCD.Systematic review registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023406950, identifier: CRD42023406950.

REM sleep deprivation induced by the modified multi-platform method has detrimental effects on memory: A systematic review and meta-analysis

The modified multi-platform method (MMPM) is used to induce animal models of paradoxical sleep deprivation and impairs memory in rodents. However, variations in MMPM protocols have contributed to inconsistent conclusions across studies. This meta-analysis aimed to assess the variations of the MMPM and their effects on memory in rats and mice. A comprehensive search identified 60 studies, and 50 were included in our meta-analysis. Overall, the meta-analysis showed that the MMPM significantly reduced the percentage of time spent in target quadrants (I2 = 54 %, 95 % confidence interval [CI] = [-1.83, -1.18]) and the number of platform-area crossings (I2 = 26 %, 95 % CI = [-1.71, -1.07]) in the Morris water maze (MWM) and shortened the latency to entering the dark compartment in the passive avoidance task (I2 = 68 %, 95 % CI = [-1.36, -0.57]), but it increased the number of errors in the radial arm water maze (RAWM) (I2 = 59 %, 95 % CI = [1.29, 2.07]). Additionally, mice performed worse on the MWM, whereas rats performed worse on the passive avoidance task. More significant memory deficits were found in cross-learning and post-learning MMPM in the MWM and RAWM, respectively. This study provided evidence that the MMPM can be used in preclinical studies of memory deficits induced by paradoxical sleep deprivation.

Air quality improvement and cognitive function benefit: Insight from clean air action in China

INTRODUCTION

Epidemiological evidence suggests associations between long-term exposure to air pollution and accelerated cognitive decline. China implemented a strict clean air action plan in 2013; however, it is unclear whether the improvement of air quality has alleviated cognitive impairment in the population.

METHODS

From the China Health and Retirement Longitudinal Study, 8536 Chinese adults were enrolled in 2011 and followed up in 2015. Satellite-based spatiotemporal models were used to estimate exposure to air pollutants (including particles with diameters ≤1.0 μm [PM₁], ≤2.5 μm [PM_2.5], ≤10 μm [PM₁₀], nitrogen dioxide [NO₂], and ozone [O₃]). Cognitive function was evaluated using a structured questionnaire in three dimensions: episodic memory, orientation and attention, and visuoconstruction. The associations between changes in the levels of air pollutants and cognitive function were elucidated by a logistic model. The Bayesian Kernel Machine Regression (BKMR) model was applied to evaluate the cumulative effect of air pollutants.

RESULTS

The mean (standard deviation) age of all participants was 58.6 (8.7) years. The odds ratio (95% confidence interval) between the highest and the lowest quartile of PM₁ exposure reduction for cognitive impairment was 0.46 (0.41, 0.53) after adjusting for confounders. Similar protective effects of cognitive function were observed with the decrease in the level of PM_2.5 (0.34 [0.30, 0.39]), PM₁₀ (0.54 [0.48, 0.62]), and NO₂ (0.59 [0.51, 0.67]), while the reduction in O₃ appeared to be less related to changes in cognitive function (OR: 0.97 [0.85, 1.10]). The protective association of PM₁ reduction was stronger in males than in females. Decreased in PM_2.5 dominate the cognitive function benefit relative to PM₁, PM₁₀, NO₂.

CONCLUSIONS

The implementation of the clean air action plan led to a significant reduction in PM₁, PM_2.5, PM₁₀, and NO₂, which could slow the decline of cognitive function, while a reduction in O₃ may not.

Development and validation of a nomogram for predicting mild cognitive impairment in middle-aged and elderly people

BACKGROUND

Mild cognitive impairment (MCI) is a clinical cognitive impairment state between dementia and normal aging. Early identification of MCI is beneficial, and it can delay the development of dementia. We aimed to develop and validate a prediction model to predict MCI of middle-aged and elderly people (aged 45 years and over).

METHODS

According to 478 middle-aged and elderly people (48-85 years old) from a cross-sectional study, we developed and validated a predictive nomogram. The least absolute shrinkage and selection operator (LASSO) regression model and multivariate logistic regression analysis were used to select variables and develop a prediction model. The performance of the nomogram was evaluated in terms of its discriminative power, calibration, and decision curve analysis (DCA).

RESULTS

The predictive nomogram was composed of the following: age, gender, education level, residence, and reading. The model showed good discrimination power (area under receiver-operating characteristic (ROC) curve was 0.8704) and good calibration. Similar results were seen in 10-fold cross-validation. The nomogram showed clinically useful in DCA analysis.

CONCLUSION

This predictive nomogram provides researchers with a practical tool for predicting MCI. The variables included in this nomogram were readily available. The population used for this nomogram was middle-aged and elderly people.