A person’s surroundings and daily exposure to environmental factors may be just as critical as genetic predisposition in determining the likelihood of developing dementia, according to two new studies examining urban neighborhoods and lifestyle habits.
In a study published in the journal Alzheimer’s & Dementia, researchers from Stockholm University and the Karolinska Institute followed 2,993 adults aged 60 and older from the Kungsholmen district of central Stockholm for up to 16 years. The researchers discovered that older adults living in areas with more vegetation within 330 feet, or 100 meters, of their front doors had about a 20 percent lower risk of developing dementia compared to those surrounded by less plant life.
Lead study author Cecilia Stenfors, an associate professor of psychology at Stockholm University, emphasized that the immediate vicinity outside a person’s home plays a vital role in preserving cognitive health as people age.
The protective buffer of plants
Using satellite imagery captured during the growing season, the Swedish researchers evaluated plant coverage at three distinct radii: 100 meters, 250 meters and 500 meters. The association between greenery and reduced dementia risk was strongest within the 100-meter zone and faded across wider distances, Earth.com reported.
The study, which confirmed dementia diagnoses across 477 participants over an average follow-up of nearly a decade, controlled for road noise, smoking, income, education, physical activity and ambient air pollution. The protective association was particularly pronounced among female participants, who experienced an estimated 31 percent drop in dementia risk linked to the set increase in greenery, compared to an uncertain seven percent decline among male participants.
Researchers suggested that nearby greenery might aid brain preservation by offering psychological restoration, reducing everyday stress, improving sleep quality and providing physical barriers against extreme heat, ambient noise and exhaust fumes. The European Union had an estimated nine million residents living with dementia in 2025, a figure projected to exceed 14 million by 2050, according to Euronews.
Screening for environmental threats
Meanwhile, another investigation published in the same journal by Harvard University researchers unveiled a predictive screening model that evaluated nearly 200 environmental factors using records from the UK Biobank. The team discovered that participants who scored high for environmental risk faced almost three times the dementia danger of participants with lower scores.
The Harvard model identified 76 environmental variables strongly linked to dementia and 34 tied specifically to Alzheimer’s disease. Among the most hazardous elements were nitrogen dioxide air pollution, poor sleep and cigarette smoking. In contrast, behaviors such as physical exercise, cohabitation with a partner, and diets featuring poultry and cheese correlated with reduced risk.
Chirag Patel, an associate professor at Harvard Medical School who co-authored the paper alongside postdoctoral fellow Chenshuang Li, noted that environmental circumstances can match genetic markers in shaping dementia outcomes. While the presence of an ApoE gene variant has long been considered a primary indicator for Alzheimer’s vulnerability, Patel noted that an exposome-wide approach offers fresh ways to identify vulnerable populations.
Urban planning and future clinical trials
Both research teams stressed that their findings demonstrate correlation rather than direct causation. However, researchers are already taking steps to probe whether environmental interventions can actively prevent cognitive decline.
Patel and Li are collaborating with colleagues at the Harvard T.H. Chan School of Public Health to design experiments intended to establish definitive causal pathways between environmental triggers and dementia. The scientists noted that their risk-scoring system could soon help clinicians identify candidates who might benefit most from early diagnostic screening or clinical trials.
In Sweden, Stenfors pointed to the findings as an urgent call for city planners to integrate functional nature into residential development. Incorporating accessible trees, lawns and gardens around homes could serve as a practical public health intervention to support cognitive resilience across aging urban communities worldwide.
