Research

Does living near busy roads increase risk of dementia?

There were several news reports today that suggested living near busy roads could increase your risk of dementia.

This news is based on research from Canada, which studied over 6 million people living in Ontario over a 10-year period. The researchers found that living near a busy road was associated with a small increase in risk of developing dementia.

This large and long term study adds to previous evidence that environmental factors could contribute towards our risk of dementia.

But while the results warrant further investigation they do not show that heavy traffic causes dementia. It remains unclear which aspect of living near a busy road – for example traffic noise or air pollution - is related to dementia risk.

What was the study, and what were the key findings?

The researchers studied medical records that were taken between 2001 and 2012 for 6.6 million adults aged between 20 and 85 living in Ontario, Canada. The researchers used these medical records to find out whether someone had a diagnosis of dementia, Parkinson’s disease or multiple sclerosis. The researchers used postcodes to work out how close people lived to major roads such as motorways or busy arterial roads.

The researchers then analysed whether people who lived near busy roads were more likely to develop dementia than those who lived further away. People who lived within 50 m of a busy road had the highest increased risk, although those who lived up to 200 m away also saw a slightly increased risk. In both cases the increase in risk was small – for those living 50 m away, the risk was 7% higher than those living 300 m or more away from a busy road. For those living within 200 m, the risk of developing dementia was increased by 2%.

The study did not find any association between living near a busy road and risk of Parkinson’s disease or multiple sclerosis, although this could be because the number of people who developed these conditions was too small to find see any patterns.

Does this mean that heavy traffic or air pollution causes dementia?

This research does not provide evidence that living near a busy road directly contributes towards the development of dementia. It is also not clear from the study which element of living near a busy road was related to dementia risk – for example, whether it could be air pollution, traffic noise or another factor.

However, this type of research is very important as we need large, long-term studies to understand more about how the environment can influence risk of dementia. These results certainly warrant further and more detailed investigation.

Whilst the researchers took aspects such as age, economic status and other medical conditions into account in their analysis, there could be other contributing factors that were not included in the study. People who live near busy roads may have increased levels of stress or have trouble sleeping, both of which have been linked to increased risk of dementia in the past.

Previous research has indicated that a form of iron oxide found in air pollution called magnetite can enter the human brain. Whilst it is unclear if magnetite or air pollution has any role in the development of dementia, these are questions that require further research.

If I live near a busy road should I be worried about my risk of dementia?

Currently we do not know enough to say for sure whether living near a busy road can increase dementia risk. There is increasing evidence that factors in our environment may play a role in our overall risk of dementia, but we need to conduct more research to understand which factors are more important.

There are other lifestyle factors that are known to have a greater influence on the risk of developing dementia than the results found today. The best ways to reduce your risk of dementia remain to eat a healthy, balanced diet, do plenty of exercise, keep your blood pressure in check and stop smoking.