Findings from a recently published research has revealed that urban air pollution, mostly from vehicles, is associated with an increased risk of dementia. The researchers reported in medical journal BMJ Open that the link remained after heavy drinking, smoking and other well established risk factors for dementia were ruled out. Worldwide, about seven per cent of people over 65 years of age suffer from Alzheimer's or some form of dementia. This risk increases by 40 per cent for people above the age of 85 years. Posing a huge challenge to healthcare systems, the number of people suffering from dementia is expected to nearly triple by 2050. The researchers wrote that primary prevention of all dementia will be a major global public health concern for the coming decades.
It was known already that chemicals cast off by tailpipe pollution including nitrogen dioxide (NO2) and soot can increase risk of heart disease, stroke and respiratory problems, especially asthma. But if this pollution can also lead to Alzheimer's and other kinds of dementia was unclear till this time.
Hence, a team of researchers led by Iain Carey of the University of London's Population Health Research Institute scoured health records of 131,000 people living in Greater London who, in 2004, were aged 50 to 79 years. None showed signs of dementia when the study began. Based on residential addresses, the scientists estimated yearly exposure to both NO2 and fine particulates known as PM 2.5, and then tracked the health of the participants over a seven-year period. During that period, nearly 2,200 patients were diagnosed with dementia. A fifth of these patients residing in the most heavily-polluted areas were 40 per cent more likely to be afflicted than the fifth residing in areas with the least NO2 and PM 2.5.
The team cautioned that no firm conclusions can be drawn as to cause-and-effect, because the study was based on after-the-fact analysis rather than a clinical trial in an experimental setting. But the findings strongly suggest that chemical byproducts of burning diesel and petrol can damage brain function.
The study also noted that earlier it was found that traffic-related air pollution can lead to poorer cognitive development in young children. And even if the impact of air pollution remains relatively modest, the public health gains would be significant if it emerged that curbing exposure might delay progression of dementia. The latest study was welcomed by experts who reviewed it before publication.
A professor of occupational and environmental health at the University of Manchester, Martie Van Tongeren, said that there is a growing body of evidence of the link between air pollution and brain health, including dementia and Alzheimer's.
Kevin McConway of the Open University noted that the study only estimated exposure to pollutants at home, and did not account for NO2 and PM 2.5 levels at or near the places of work, or the amount of time spent away from home.
The European Environment Agency has estimated that every year more than 400,000 people in Europe's urban areas die prematurely due to outdoor air pollution.
Similar research by medical professional should be conducted in Bangladesh to determine whether air pollution is increasing the number of dementia and Alzheimer's patients.
Several studies by World Bank and other international organisations have recently noted that at least 80,000 people die in the country every year from ailments related to pollution.
Sarwar Md. Saifullah Khaled is a retired Professor of Economics, BCS General Education Cadre.
