How dementia could be linked to air pollution in early life
Researchers in Scotland have found patterns in health data that suggest that air pollution breathed by children may affect their chances of getting dementia in later life.
The first clue that air pollution may affect brain health was discovered about 20 years ago, when researchers found brain changes in pet dogs in chronically polluted Mexico City.
By 2022, a UK government committee was able to review 69 studies. They concluded it was likely that air pollution accelerated cognitive decline in later life and increased the risk of dementia. They also found some evidence of changes in the brains of children exposed to air pollution.
Otto-Emil Jutila, from the University of Edinburgh and first author of the new study, said: “While air pollution’s role as a late-life risk factor for dementia has been extensively investigated, less is known about the impact of air pollution across the whole of our lives.”
Starting a project tracking young people today would mean a long delay in tackling the problems.
In 2004, just over 1,000 people were recruited for a study on brain and ageing. They were all born in 1936 and grew up around Edinburgh. From age 70, they have been assessed every three years.
The first person was diagnosed with dementia in 2011. By 2019, 17% of the people had acquired dementia, around one in six.
The next stage was to work out the air pollution in their childhood neighbourhoods. Dr Massimo Vieno, from the UK Centre for Ecology and Hydrology (UKCEH), said: “Nowadays the UK is a very data-rich country, but there is limited data on historical fuel uses, industry and transport.”
Sam Tomlinson, also from UKCEH, added: “Data were constructed from myriad sources, old journals, books, statistical compendiums etc. Given coal’s intrinsic ties to the British population for centuries, it was important to estimate how much (and where) coal was consumed throughout the 20th century.”
The results did not reach full statistical significance, but several patterns emerged.
The first, and strongest result, was that air pollution in 1936 was positively associated with the risk of dementia, including Alzheimer’s disease. At this time, the study participants were in their mother’s womb or less than a year old.
The second was more curious. Air pollution in mid-life seemed to have a protective effect for dementia but this may be owing to the time taken for different air pollution diseases to develop.
Jutila said: “Higher midlife exposure may be associated with earlier death from other air pollution-related conditions, such as cardiovascular and respiratory disease, before people can develop dementia.
“Air pollution exposure is a life-course problem with long-term detrimental effects on health. Our study reinforces the importance of reducing air pollution exposure throughout life, especially during vulnerable periods in the prenatal and early childhood.”
Although not conclusive, the new study shows that research on the health of older people, and the air pollution that they breathed in the past, may help to protect future generations.
Better quality air may help people in later life, too. Studies in France, the US and China found that reducing air pollution could quickly reduce the number of people who got dementia.
