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Air pollution likely to exacerbate dementia risk, meta-study finds

Air pollution is likely to increase the risk of developing dementia, a government research group has found.

The Committee on the Medical Effects of Air Pollutants (CMEAP) reviewed nearly 70 studies in human populations which have examined the possible link between air pollutants and effects on mental ability and dementia.

It found that the studies show “it is likely” that air pollution can contribute to a decline in mental ability and dementia in older people.

It is already known that air pollution, particularly small particle pollution, can affect the heart and the circulatory system, including circulation to the brain. These effects are linked to a form of dementia caused by damage to the blood vessels in the brain.

Experimental studies suggest that air pollution might also stimulate the immune cells in the brain, which can then damage nerve cells.

It is not clear whether this effect is important at the levels of pollution which occur in the UK today, but it is likely that some very small air pollution particles can enter the brain, and may cause direct damage. However, CMEAP said that based on the current evidence, it does not seem likely that this is an important mechanism for the development of dementia.

The committee refrained from making recommendations on how to quantify the effects of air pollution on dementia because it is too difficult to combine the results of the currently available studies in an appropriate way, although it urges further research into the topic in order to develop a stronger evidence base.

Studies are split over which pollutant is most associated with these effects, it added.

It is estimated that around 20 per cent of people over the age of 65 have mild cognitive impairment. Although, the mild form of this condition often has little effect on daily life, 5 to 10 per cent of people with it will develop dementia, often considered one of the greatest global health challenges in the 21st century.

Around 850,000 people in the UK suffer with dementia, according to the NHS.

A study based on California earlier this year showed that improving air quality appears to slow cognitive decline and reduce the risk of developing dementia in older women.

Last month, the National Audit Office said that UK government initiatives to cut air pollution have “not moved as fast as expected” and it is unclear how current 2030 targets will be met.

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