Fine Particulate Matter Associated With Increased Risk of Alzheimer Disease, Study Suggests

Findings from a study published in PLOS Medicine suggest that exposure to fine particulate matter (particles ≤ 2.5 µm, or PM2.5) was associated with an increased risk of Alzheimer disease, particularly through direct pathways instead of comorbidity-mediated pathways. The authors urged air quality interventions to promote and support dementia prevention strategies, particularly those that overlap environmental and clinical domains.¹

Environmental Factors Influence Health and Are Linked to Adverse Conditions

Research data consistently demonstrate that environmental factors, particularly air pollution and exposure to PM2.5 and PM10, have harmful effects on human health and contribute to a range of adverse conditions. For example, long-term and seasonal increases in ambient particulate pollution have been linked to higher rates of respiratory disease exacerbations and emergency department admissions for patients with asthma and chronic obstructive pulmonary disease, with pollution playing a major role in worsening symptoms beyond the influence of temperature and humidity.² Additionally, prolonged exposure to specific components of PM2.5, such as sulfate, elemental carbon, and soil dust, has been associated with an increased risk of depression among older adults, underscoring the broad impact of air pollution on mental as well as physical health.³

Beyond respiratory and mental health effects, long-term exposure to high levels of PM2.5 has also been tied to early signs of cardiovascular damage, including diffuse myocardial fibrosis—a form of heart tissue scarring that can precede heart failure—highlighting the systemic risks posed by persistent environmental pollution even at levels below global guidelines.⁴

Air pollution and several common comorbidities (eg, hypertension, stroke, depression) are established risk factors for Alzheimer disease; however, whether these comorbidities mediate or amplify the effects of PM2.5 on Alzheimer disease is not clear. For this study, the authors investigated whether these conditions modify or mediate the association between PM2.5 exposure and incident Alzheimer disease.¹

What Did This Study Find?

The authors conducted a nationwide cohort study of about 27.8 million US Medicare beneficiaries aged 65 and older from 2000 to 2018. Exposure to PM2.5 was assessed using high-resolution air pollution data sets. Additionally, Cox proportional hazards models were applied to estimate the associations between exposure to PM2.5, incident Alzheimer disease, and any comorbidities. The potential for comorbidities to modify and mediate the association between PM2.5 and Alzheimer disease was evaluated by stratified analyses and mediation analysis.¹

The findings identified approximately 3.0 million incident cases of Alzheimer disease, and PM2.5 exposure (5-year moving average prior to disease onset) was associated with an increased risk of Alzheimer disease in the overall population (HR per IQR increase [IQR, 3.8 µg/m³], 1.085 [95% CI, 1.078-1.091]). Of note, this association was observed to be somewhat stronger in individuals with stroke (HR per IQR increase, 1.105 [95% CI, 1.096-1.114]), but there was little effect modification for hypertension and depression. Additionally, PM2.5 exposure was also significantly associated with higher risks of hypertension, depression, and stroke, all of which were also linked to increased Alzheimer disease risk; however, mediation effects were minimal, with approximately 1.6% of the association between PM2.5 and incident Alzheimer disease mediated by hypertension, 4.2% by stroke, and 2.1% by depression.¹

Study limitations include the use of administrative claims data and potential misclassification of exposure from area-level PM2.5 estimates.¹

Pharmacists can translate emerging evidence on PM2.5 exposure and Alzheimer disease risk into practical prevention and education for patients. Because the data from this study suggest that PM2.5 may increase Alzheimer risk largely through direct pathways rather than comorbidity-mediated ones,¹ pharmacists can help broaden prevention conversations beyond traditional cardiovascular risk reduction.

In both community and health system settings, pharmacists can educate patients—especially older adults and caregivers—about environmental health as a legitimate dementia risk factor, encourage awareness of local air quality alerts, and recommend simple exposure-reduction strategies during high pollution days (eg, limiting outdoor activity, using indoor air filtration when feasible). Pharmacists can also reinforce management of related comorbidities, such as hypertension, depression, and stroke, which remain independently linked to Alzheimer risk. Additionally, pharmacists and other health care professionals can advocate for public health interventions that support cleaner air as part of long-term cognitive health promotion.

REFERENCES

1. Deng Y, Liu Y, Hao H, et al. The role of comorbidities in the associations between air pollution and Alzheimer’s disease: a national cohort study in the American Medicare population. PLoS Med. 2026;23(2):e1004912. doi:10.1371/journal.pmed.1004912

2. McGovern G. Air pollution and seasonal variability associated with asthma- and COPD-related hospital admissions. Pharmacy Times. January 20, 2025. Updated November 25, 2025. Accessed February 18, 2026. https://www.pharmacytimes.com/view/air-pollution-and-seasonal-variability-associated-with-asthma--and-copd-related-hospital-admissions

3. Gerlach A. Study links specific air pollution components to increased depression risk in older adults. Pharmacy Times. December 29, 2025. Updated January 5, 2026. Accessed February 18, 2026. https://www.pharmacytimes.com/view/study-links-specific-air-pollution-components-to-increased-depression-risk-in-older-adults

4. McGovern G. Study: high long-term exposure to fine particulate air pollution is associated with diffuse myocardial fibrosis. Pharmacy Times. July 7, 2025. Updated July 9, 2025. Accessed February 18, 2026. https://www.pharmacytimes.com/view/study-high-long-term-exposure-to-fine-particulate-air-pollution-is-associated-with-diffuse-myocardial-fibrosis