Air pollution may lead to increased dementia risk finds new study
Air pollution has been previously linked to heart disease, stroke and respiratory disease, but its potential role in neurodegenerative diseases, such as dementia,has not been studied.
That is why English researchers studied estimates of air and noise pollution levels across Greater London to assess potential links of pollution with new dementia diagnoses. They used data of 131,000 patients aged 50 to 79 in 2004, who had not been diagnosed with dementia, were registered at 75 general practices located within the London orbital M25 motorway.
Based on the residential postal codes of these patients, the researchers estimated their yearly exposure to air pollutants-specifically nitrogen dioxide (NO2), fine particulate matter (PM2.5), and ozone (O3) as well as proximity to heavy traffic and road noise, using verified recorded measurements.
“Traffic related air pollution has been linked to poorer cognitive development in young children, and continued significant exposure may produce neuroinflammation and altered brain innate immune responses in early adulthood.”
The health of these patients was then observed for average of 7 years, until a diagnosis of dementia, death, or deregistration from the practice, whichever came first. During the monitoring period, 2181 patients (1.7%) were diagnosed with dementia, including Alzheimer’s disease. These diagnoses were associated with ambient levels of NO2 and PM2.5, estimated at the patients’ homes at the start of the monitoring period in 2004.
This is in line with a recent report by WHO that estimated that 7 million people die every year of diseases caused by ambient (outdoor) and household air pollution. Of the 15 most polluted cities in the world, 14 are in India, said the report. Findings of this new study therefore have grave implications for India.
The English study found that individuals living in the top fifth of NO2 levels ran a 40 per cent higher risk of being diagnosed with dementia than those living in the bottom fifth. A similar increase in risk was observed for higher PM2.5 levels.
These associations were consistent and unexplained by known influential factors, such as smoking and diabetes. Authors concluded, “Traffic related air pollution has been linked to poorer cognitive development in young children, and continued significant exposure may produce neuroinflammation and altered brain innate immune responses in early adulthood.”