Air pollution increases risk of dementia

By Dr. Ananya Mandal, MDSep 18 2018

A new study has shown that air pollution raises the risk of dementia. The risk remains among people of all ages find researchers.

The data based in London shows that persons over the age of 50 who are living in regions that have greater concentrations of nitrogen oxide have a 40 percent greater risk of developing dementia compared to people who live in areas with lower NOx pollution. The results of the study appeared in the latest issue of the BMJ Open Journal this week.

Image Credit: Aizuddin Saad / Shutterstock

The researchers explain that there was no direct connection between dementia and air pollution but there seems to be a connection between the two that cannot be explained by other risk factors. Air pollution has been associated with heart disease and respiratory disease said Professor Frank Kelly, of environmental health at King’s College London. This is the first study that shows an association of air pollution with a neurodegenerative disease he explained. He said there is sufficient information to suggest air pollution as a risk factor for dementia. He explained that around 60,000 cases of the total 850000 dementia patients (approximately 7 percent) in United Kingdom could be related to higher air pollutant exposure.

Air pollution has recently come under the scanner with a study finding pollutants crossing over into the placenta of the pregnant women and yet another study in China showing exposure to air pollutants causing impairment of intelligence in children. This loss of intelligence is equal to the loss of around a year of education among the children the researchers had found. This new study from Kings College serves to add to these earlier studies.

The study looked at the air and noise pollution at various parts of London and compared it with patient health records for nearly 131,000 patients between ages 50 and 79 years. The records were anonymised and were obtained from 75 GP clinics within M25. The health records of these patients were followed for seven years since 2005 provided by a governmental, not-for-profit service called the Clinical Practice Research Datalink. During the study period, 1.7 percent of the patient population developed dementia. The dementia risk was correlated with the home postcodes of the patients.

While this study adds to the earlier research on the detrimental effects of air pollution, it does not individually track all the lifestyle factors that could be associated with dementia. Furthermore individual exposure to air pollutants is also not specifically studied and connected with dementia risk.

According to the authors of the paper, “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.” This inflammation could be the reason behind the association of the air pollutants and dementia they explain.

Iain Carey, a senior lecturer of epidemiology in the Population Health Research Institute at St. George's University of London and lead author of the paper said, “While the findings need to be treated with caution, the study is an important addition to the growing evidence for a possible link between traffic pollution and dementia.” He said that this study would encourage further research to understand the connection between air pollution and dementia better.

Alternative fuels and motorized vehicles, safe cycling avenues, smoking cessation and also affordable and easy public transport are some of the ways to bring down air pollution as are regulations that reduce auto-emissions. The number of dementia cases in UK could soon climb from the present 850,000 to 1 million by 2025 and 2 million by 2050 say health authorities. According to the World Health Organization globally there are 47 million people living with Alzheimer's disease and other dementias and this number is set to rise to 75 million by 2030 and become triple the numbers by 2050.