Air Pollution: A Silent Key Driver of Dementia

Urban air pollution and child neurodevelopmental conditions: a systematic bibliometric review

PURPOSE OF REVIEW

Using advanced bibliometric analysis, we systematically mapped the most current literature on urban air pollution and neurodevelopmental conditions to identify key patterns and associations. Here, we review the findings from the broader literature by discussing a distilled, validated subset of 44 representative studies.

RECENT FINDINGS

Literature highlights a complex relationship between environmental toxins, neurodevelopmental disorders in children, and neurobehavioral pathways involving oxidative stress, neuroinflammation, and protein aggregation. Chronic prenatal and postnatal exposure to airborne pollutants - such as particulate matter and heavy metals - may contribute to early formation of amyloid plaques through preadolescence. These processes may compromise synaptic plasticity and neural integrity, which can progressively induce cognitive, emotional, and behavioral dysregulation, sharing some pathological features traditionally associated with adult neurodegenerative diseases.

SUMMARY

The interactions between air pollution exposure levels, developmental timing, and factors such as genetic vulnerability associated with neurodevelopmental disorders are still undetermined. However, accelerated neurodegenerative processes leading to cognitive decline and suboptimal mental health in children and adolescents seem most likely linked with pollutants penetrating the blood-brain barrier, and inducing oxidative stress and neuroinflammation. Urgent precautionary action might reduce environmental exposures during critical early developmental periods, thereby safeguarding children's cognitive function and mental health.

Iron Trace Elements Concentration in PM10 and Alzheimer's Disease in Lima, Peru: Ecological Study

Alzheimer's disease (AD) has been linked to air pollution, especially particulate matter (PM). PM comprises various elements, including iron-rich particles that may reach the brain through inhalation. Lima, Peru is one of the most polluted cities in Latin America, with a high rate of AD. The study aims to evaluate the association between iron (Fe) trace elements in PM10 and AD cases in Lima, Peru. This retrospective ecological study used monthly Fe concentration data from the Peruvian Ministry of Health. AD cases (ICD-10-G30) and dementia in AD cases (DAD, ICD-10-F00) were obtained from the Peruvian CDC. Fe trace element data were available for six districts in Lima for the years 2017-2019 and 2022. Cases were standardized based on ≥60-year-old populations of each district. Hierarchical mixed-effects models of Gaussian and negative binomial families were constructed to evaluate both outcomes jointly (AD + DAD) and separately (AD, and DAD). A sensitivity analysis was conducted by excluding data from Lima's downtown district. In the complete model, log-Fe concentration was associated with a higher rate of AD + DAD and DAD, and with a higher IRR for the three outcomes. After controlling for other metals, a higher DAD rate was observed (β-coeff = 6.76, 95%CI 0.07; 13.46, p = 0.048), and a higher IRR for AD + DAD (1.55, 95%CI 1.09; 2.20, p = 0.014) and DAD (1.83, 95%CI 1.21; 2.78, p = 0.004). The association was not significant in the sensitivity analysis. In conclusion, exposure to Fe through PM10 inhalation may be associated with the presence of AD in Lima.

Access to urban green spaces and use of social services and institutional long-term care among older people in Malmö, Sweden: a longitudinal register study

BACKGROUND

Finding ways to prolong independence in daily life among older people would be beneficial for both individuals and society. Urban green spaces have been found to improve health, but only a few studies have evaluated the association between urban green spaces and independence in daily life. The aim of this study was to assess the long-term effect of urban green spaces on independence in daily life, using social services and support, mobility aids, and relocation to institutional long-term care as proxies, among community dwelling people 65 + years.

METHODS

We identified 40 357 people 65 + years living in the city of Malmö, Sweden in 2010. Using geographical information systems (GIS), we determined the amount of urban green spaces (total, public, and quiet) within 300 m of each person's residence. All three measures were categorized based on their respective percentiles, so that the first quartile represented the 25% with the least access and the fourth quartile the 25% with the most access. In 2015 and 2019, we assessed the outcomes minor assistance (non-personal support), major assistance (personal support), and relocation into institutional long-term care. These three outcome measures were used as proxies for independence in daily life. The effect of amount of urban green spaces in 2010 on the three outcomes in 2015 and 2019, respectively, was assessed by pairwise comparing the three highest quartiles to the lowest.

RESULTS

Compared to the lowest quartile, those in the highest quartile of quiet green spaces in 2010 were less likely to receive minor assistance in both 2015 and 2019. Besides this, there were no indications that any of the measures of urban green space affected independence in daily life at the five- and nine-year follow-up, respectively.

CONCLUSION

Although urban green spaces are known to have positive impact on health, physical activity, and social cohesion among older people, we found no effect of total, public, or quiet green spaces on independence in daily life. This could possibly be a result of the choice of measures of urban green spaces, including spatial and temporal aspects, an inability to capture important qualitative aspects of the green spaces, or the proxy measures used to assess independence in daily life.

Environmental risk factors provoke new thinking for prevention and treatment of dementia with Lewy bodies

In recent years, environmental factors have received attention in the pathogenesis of neurodegenerative diseases. Other than genetic factors, the identification of environmental factors and modifiable risk factors may create opportunities to delay the onset or slow the progression of Lewy body disease. Researchers have made significant progress in understanding environmental and modifiable risk factors over the past 30 years. To date, despite the increasing number of articles assessing risk factors for Lewy body disease, few reviews have focused on their role in its onset. In this review, we reviewed the literature investigating the relationship between Lewy body disease and several environmental and other modifiable factors. We found that some air pollutants, exposure to some metals, and infection with some microorganisms may increase the risk of Lewy body disease. Coffee intake and the Mediterranean diet are protective factors. However, it is puzzling that low educational levels and smoking may have some protective effects. In addition, we proposed specific protocols for subsequent research directions on risk factors for neurodegenerative diseases and improved methods. By conducting additional case-control studies, we could explore the role of these factors in the etiopathogenesis of Lewy body disease, establishing a foundation for strategies aimed at preventing and reducing the onset and burden of the disease.

Leading determinants of incident dementia among individuals with and without the apolipoprotein E ε4 genotype: a retrospective cohort study

BACKGROUND

Little is known regarding the leading risk factors for dementia/Alzheimer's disease (AD) in individuals with and without APOE4. The identification of key risk factors for dementia/Alzheimer's disease (AD) in individuals with and without the APOE4 gene is of significant importance in global health.

METHODS

Our analysis included 110,354 APOE4 carriers and 220,708 age- and sex-matched controls aged 40-73 years at baseline (between 2006-2010) from UK Biobank. Incident dementia was ascertained using hospital inpatient, or death records until January 2021. Individuals of non-European ancestry were excluded. Furthermore, individuals without medical record linkage were excluded from the analysis. Moderation analysis was tested for 134 individual factors.

RESULTS

During a median follow-up of 11.9 years, 4,764 cases of incident all-cause dementia and 2065 incident AD cases were documented. Hazard ratios (95% CIs) for all-cause dementia and AD associated with APOE4 were 2.70(2.55-2.85) and 3.72(3.40-4.07), respectively. In APOE4 carriers, the leading risk factors for all-cause dementia included low self-rated overall health, low household income, high multimorbidity risk score, long-term illness, high neutrophil percentage, and high nitrogen dioxide air pollution. In non-APOE4 carriers, the leading risk factors included high multimorbidity risk score, low overall self-rated health, low household income, long-term illness, high microalbumin in urine, high neutrophil count, and low greenspace percentage. Population attributable risk for these individual risk factors combined was 65.1%, and 85.8% in APOE4 and non-APOE4 carriers, respectively. For 20 risk factors including multimorbidity risk score, unhealthy lifestyle habits, and particulate matter air pollutants, their associations with incident dementia were stronger in non-APOE4 carriers. For only 2 risk factors (mother's history of dementia, low C-reactive protein), their associations with incident all-cause dementia were stronger in APOE4 carriers.

CONCLUSIONS

Our findings provide evidence for personalized preventative approaches to dementia/AD in APOE4 and non-APOE4 carriers. A mother's history of dementia and low levels of C-reactive protein were more important risk factors of dementia in APOE4 carriers whereas leading risk factors including unhealthy lifestyle habits, multimorbidity risk score, inflammation and immune-related markers were more predictive of dementia in non-APOE4 carriers.

Current perspectives on prevention of vascular cognitive impairment and promotion of vascular brain health

INTRODUCTION

The true global burden of vascular cognitive impairment (VCI) is unknown. Reducing risk factors for stroke and cardiovascular disease would inevitably curtail VCI.

AREAS COVERED

The authors review current diagnosis, epidemiology, and risk factors for VCI. VCI increases in older age and by inheritance of known genetic traits. They emphasize modifiable risk factors identified by the 2020 Lancet Dementia Commission. The most profound risks for VCI also include lower education, cardiometabolic factors, and compromised cognitive reserve. Finally, they discuss pharmacological and non-pharmacological interventions.

EXPERT OPINION

By virtue of the high frequencies of stroke and cardiovascular disease the global prevalence of VCI is expectedly higher than prevalent neurodegenerative disorders causing dementia. Since ~ 90% of the global burden of stroke can be attributed to modifiable risk factors, a formidable opportunity arises to reduce the burden of not only stroke but VCI outcomes including progression from mild to the major in form of vascular dementia. Strict control of vascular risk factors and secondary prevention of cerebrovascular disease via pharmacological interventions will impact on burden of VCI. Non-pharmacological measures by adopting healthy diets and encouraging physical and cognitive activities and urging multidomain approaches are important for prevention of VCI and preservation of vascular brain health.