Dementia Incidence, APOE Genotype, and Risk Factors for Cognitive Decline in Aboriginal Australians: A Longitudinal Cohort Study

Adult-onset hearing loss and incident cognitive impairment and dementia - A systematic review and meta-analysis of cohort studies

BACKGROUND

We comprehensively summarized the cohort evidence to date on adult-onset hearing loss as risk factor for incident cognitive impairment and dementia, and examined the evidence for dose-response, risk for various dementia subtypes, and other moderators. Previous meta-analyses were less comprehensive.

METHODS

We included cohort studies with participants without dementia and with hearing assessments at baseline, minimum 2 years follow-up and incident cognitive outcomes. We used random-effect models and subgroup and meta-regression on moderator analyses.

RESULTS

We identified fifty studies (N=1,548,754). Hearing loss (yes/no) was associated with incident dementia risk (HR=1.35 [95% CI = 1.26 - 1.45), mild cognitive impairment (MCI HR=1.29 [95% CI = 1.11 - 1.50]), cognitive decline not specified as MCI or dementia (HR=1.29 [95% CI = 1.17 - 1.42]), and Alzheimer's disease dementia (ADD, HR=1.56 [95% CI = 1.30 - 1.87]), but not with vascular dementia (HR, 1.30 [95% CI = 0.83 - 2.05]). Each 10-decibel worsening of hearing was associated with a 16% increase in dementia risk (95% CI = 1.07 - 1.27). The effect of hearing loss did not vary across potential moderators.

CONCLUSIONS

Cohort studies consistently support that adult-onset hearing loss increases the risk of incident cognitive decline, dementia, MCI, and ADD.

Strength together: examining risk and protective factors associated with dementia and cognitive impairment in Aboriginal and Torres Strait Islander peoples through harmonisation of landmark studies

BACKGROUND

Rates of dementia for Aboriginal and Torres Strait Islander peoples are three to five times greater compared to non-Indigenous Australians, with earlier age of onset. However, the risk and protective factors that drive these higher rates vary across existing cohort studies, with minimal findings on the role of vascular risk factors beyond stroke. Harmonisation of data across studies may offer greater insights through enhanced diversity and strengthened statistical capabilities. This study aims to combine three landmark cohort studies of Aboriginal and Torres Strait Islander participants to better understand the determinants of cognitive health and dementia.

METHODS/DESIGN

Three cohort studies - the Kimberley Healthy Adults Project (KHAP, N = 363), Koori Growing Old Well Study (KGOWS, N = 336) and Torres Strait Dementia Prevalence Study (TSDPS, N = 274) - share a similar research methodology with demographic, medical history, psychosocial factors, cognitive tests and consensus clinical diagnoses of cognitive impairment and dementia. Associations between risk and protective factors of interest and the presence of dementia and/or cognitive impairment diagnoses will be evaluated by univariable and multivariable logistic regression in a harmonised cross-sectional cohort of 898 participants. Factors associated with incident dementia and/or cognitive impairment will be assessed in a subset of KHAP (n = 189) and KGOWS participants (n = 165) who were available in longitudinal follow-up, after exclusion of those with baseline dementia or cognitive impairment. Analyses in relation to outcome measure of death or dementia will be conducted to account for the competing risk of death. Logistic regression will be used to evaluate the association between the individual components of the 16-component Kimberley Indigenous Cognitive Assessment (KICA) tool and the presence of dementia and cognitive impairment determined by independent consensus diagnoses. Multivariable binary logistic regression will be used to adjust for the effect of confounding variables. Results will be reported as odds ratios (OR) with 95% confidence intervals (95% CI).

DISCUSSION

Greater understanding of risk and protective factors of dementia and cognitive impairment relevant to Aboriginal and Torres Strait Islander peoples may improve approaches across the life course to delay cognitive decline and reduce dementia risk.

Prevalence and risk factors for dementia and mild cognitive impairment among older people in Southeast China: a community-based study

BACKGROUND

With the aging population, the number of individuals with dementia in China is increasing rapidly. This community-based study aimed to investigate the prevalence and risk factors for dementia and mild cognitive impairment (MCI) among older adults in China.

METHODS

In this study, 20,070 individuals aged ≥ 65 were recruited between January 1, 2022, and February 1, 2023, from ten communities in Xiamen City, China. We collected data on age, sex, level of education, and medical history, as well as global cognition and functional status. The prevalence of dementia and MCI was examined, and the risk factors for different groups were assessed.

RESULTS

The overall prevalence of dementia and MCI was approximately 5.4% (95% confidence interval [CI], 5.1-5.7) and 7.7% (95% CI, 7.4-8.1), respectively. The results also indicated that dementia and MCI share similar risk factors, including older age, female sex, hypertension, and diabetes mellitus. Compared with individuals with no formal education, those with > 6 years of education had an odds ratio for MCI of 1.83 (95% CI, 1.49-2.25). We also found that only 5.5% of the positive participants chose to be referred to the hospital for further diagnosis and treatment during follow-up visits.

CONCLUSIONS

This study estimated the prevalence and risk factors for dementia and MCI among individuals aged ≥ 65 years in Southeast China. These findings are crucial for preventing and managing dementia and MCI in China.

Risk, protective, and biomarkers of dementia in Indigenous peoples: A systematic review

INTRODUCTION

Dementia is an emergent health priority for Indigenous peoples worldwide, yet little is known about disease drivers and protective factors.

METHODS

Database searches were conducted in March 2022 to identify original publications on risk, protective, genetic, neuroradiological, and biological factors related to dementia and cognitive impairment involving Indigenous peoples.

RESULTS

Modifiable risk factors featured across multiple studies include childhood adversity, hearing loss, low education attainment, unskilled work history, stroke, head injury, epilepsy, diabetes, hypertension, hyperlipidemia, depression, low BMI, poor mobility, and continence issues. Non-modifiable risk factors included increasing age, sex, and genetic polymorphisms. Education, ex-smoking, physical and social activity, and engagement with cultural or religious practices were highlighted as potential protective factors. There is a paucity of research on dementia biomarkers involving Indigenous peoples.

DISCUSSION

Greater understanding of modifiable factors and biomarkers of dementia can assist in strength-based models to promote healthy ageing and cognition for Indigenous peoples.

Co-design of dementia prevention program for Aboriginal Australians (DAMPAA)

INTRODUCTION

Dementia is highly prevalent in older Aboriginal Australians, with several modifiable risk factors. Currently, there is limited evidence on how to prevent cognitive decline in Aboriginal Australians.

METHODS

Based on our Theory of Change (ToC) framework, we co-developed the Dementia risk management and prevention program for Aboriginal Australians (DAMPAA) aged over 45 years in partnership with Aboriginal community-controlled organizations (ACCOs) and Elders. Qualitative data were collected through ACCO staff workshops, Elders yarning, and governance groups to inform the protocol. Additionally, we conducted a small pilot study.

RESULTS

Expected DAMPAA ToC outcomes are: (1) improved daily function, (2) better cardiovascular risk management, (3) falls reduction, (4) improved quality of life, and (5) reduced cognitive decline. Attendance enablers are social interaction, environment, exercise type/level, and logistics.

DISCUSSION

Findings suggest that ToC is an effective collaborative approach for co-designing Aboriginal health programs.

Excessive Dietary Salt Intake Exacerbates Cognitive Impairment Progression and Increases Dementia Risk in Older Adults

OBJECTIVES

To investigate excessive dietary salt intake as an independent risk factor of cognitive impairment and dementia in older adults.

DESIGN

Prospective, population-based cohort study.

SETTINGS AND PARTICIPANTS

Two thousand forty-one community residents aged ≥60 years were recruited between April 2007 and August 2009 from the Shandong area of China.

MEASUREMENTS

Participants were classified into low, mild, moderate, and high salt intake groups according to urinary sodium measurements for 7 consecutive days. Global cognitive function was assessed at baseline and biennially thereafter using the Mini Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Dementia Rating Scale (DRS), and Informant Questionnaire on Cognitive Decline in the Elderly. Demographics and apolipoprotein E (APOE) genotype were also obtained for each participant. Participants were monitored for 11.4 ± 2.0 years.

RESULTS

During follow-up, MMSE, MoCA, and DRS scores decreased progressively faster with increasing salt intake (P_adjustment < 0.05 among all intake groups). In total, 319 participants (13.74 per 1000 person-years) developed cognitive impairment. Compared with the low salt intake group, cognitive impairment risk was increased by 75% in the mild group (P_adjustment = 0.027), 180% in the moderate group (P_adjustment < 0.001), and 330% in the high group (P_adjustment < 0.001) after adjustment for age, education, mean, and variability in visit-to-visit systolic and diastolic blood pressure, and APOE genotype. The hazard ratio for cognitive impairment increased by 1.59 (95% CI 1.40-1.79) with each 1-SD increment in salt intake after confounder adjustment (P_adjustment < 0.001).

CONCLUSIONS AND IMPLICATIONS

Excessive dietary salt impairs cognitive function and increases cognitive impairment risk in older adults independently of known risk factors, including hypertension and APOE genotype.