Living less than 50 metres from a major road – or less than 150 metres from a highway – has been linked to significantly higher incidence of dementia and Parkinson’s disease, according to a new population-based study.
The implication is that chronic exposure to traffic pollution increases your risk of these neurological diseases, a theory supported by previous research.
The scientists from the University of British Columbia (UBC) also found evidence of a suggested link between major road proximity and Alzheimer’s disease and multiple sclerosis – but more extensive research is required to establish the association’s validity.
For the study, researchers from the UBC school of population and public health analysed data for 678,000 adults between the ages of 45 and 84 who lived in Metro Vancouver from 1994 to 1998 and during a follow-up period from 1999 to 2003.
They estimated individual exposures to road proximity, air pollution, noise and greenness (relative access to parks and gardens) at each person’s residence by using postal code data.
During the follow-up period, the researchers identified 13,170 cases of non-Alzheimer’s dementia, 4201 cases of Parkinson’s disease, 1277 cases of Alzheimer’s disease and 658 cases of MS.
For non-Alzheimer’s dementia and Parkinson’s disease specifically, living near major roads or a highway was associated with 14 per cent and seven per cent increased risk of both conditions, respectively.
The researchers also found that living near green spaces, like parks, has protective effects against developing these neurological disorders.
Due to relatively low numbers of Alzheimer’s and MS cases in Metro Vancouver compared to non-Alzheimer’s dementia and Parkinson’s disease, the researchers did not identify associations between air pollution and increased risk of these two disorders.
However, they are now analysing Canada-wide data and are hopeful the larger dataset will provide more information on the effects of air pollution on Alzheimer’s disease and MS.
“For the first time, we have confirmed a link between air pollution and traffic proximity with a higher risk of dementia, Parkinson’s, Alzheimer’s and MS at the population level,” says Weiran Yuchi, the study’s lead author and PhD candidate.
“The good news is that green spaces appear to have some protective effects in reducing the risk of developing one or more of these disorders. More research is needed, but our findings do suggest that urban planning efforts to increase accessibility to green spaces and to reduce motor vehicle traffic would be beneficial for neurological health.”
When the researchers accounted for green space, they found the effect of air pollution on the neurological disorders was mitigated. The researchers suggest that this protective effect could be due to several factors.
“For people who are exposed to a higher level of green space, they are more likely to be physically active and may also have more social interactions,” said Dr Michael Brauer, the study’s senior author and professor in the UBC school of population and public health.
“There may even be benefits from just the visual aspects of vegetation.”
Dr Brauer added that the findings underscore the importance for city planners to ensure they incorporate greenery and parks when planning and developing residential neighbourhoods.
A 2015 study found that long-term exposure to air pollution can cause damage to brain structures and impair cognitive function in middle-aged and older adults.
A 2018 study linked exposure to residential air pollution during foetal life with brain abnormalities that may contribute to impaired cognitive function in school-age children.
In April, The New Daily reported that a study of more than a million people had found that children who grew up with the lowest levels of green space – parks, gardens and sports fields – had up to a 55 per cent higher risk of developing a psychiatric disorder.