The scary link between your daily commute and Alzheimer’s

Can’t get enough of city living? According to a new study published in the British Medical Journal, there’s at least one reason you should probably consider moving to a less congested area. Danish researchers have collected compelling evidence suggesting long-term exposure to traffic noise (via cars or trains) is linked to an increased risk of developing dementia, particularly Alzheimer’s.

The connection between traffic noise and dementia

Blaring car alarms or police sirens at two o’clock in the morning are no doubt annoying, but these findings give an entirely different meaning to the phrase “silence is golden.” This was no small research project either: Roughly two million Danish adults ages 60 and up were tracked between 2004 and 2017 for an average of eight and half years. Researchers compared dementia outcomes with each person’s estimated exposure to traffic noise based on their residential address.

While dementia risk has been linked to a number of physical health and lifestyle factors such as cardiovascular disease or a sedentary lifestyle, there’s scientific reason to believe that environmental considerations influence dementia outcomes as well.

For example, recent research has connected air pollution to elevated dementia risk. Coincidentally, air pollution is usually more of a problem in urban areas and cities. Now it appears that city sounds, as well as the air, may be putting many residents at further risk of Alzheimer’s.

Moreover, while prior research has linked transportation noise pollution to various physical problems such as obesity or diabetes, the relationship between noise pollution and dementia has remained unclear. In pursuit of some answers, the research team conducted this study. 

It’s worth mentioning that researchers even went so far as to estimate average traffic noise pollution levels from both the most and least exposed sides of each and every included residential address in Denmark. In other words, the amount of traffic noise an individual living in a street-facing apartment would hear versus another apartment deep within said building.

An analysis of the dataset described above revealed 103,500 new cases of dementia during the study period. After being careful to consider other potentially influential dementia risk factors (lifestyle choices, etc), study authors found that being exposed to both road and railroad traffic noise for an average of 10 years was associated with a higher risk of dementia. This held true for both the most and least exposed sides of buildings.

Importantly, the results suggest greater overall traffic noise exposure is more detrimental than louder traffic noises in general. For example, hearing a loud car alarm for two minutes may be preferable to hearing that same alarm at a lower volume for 25 minutes straight.

Both road traffic and train noise pollution were linked to an increased risk of Alzheimer’s specifically. Exposure to car noises of 55 dB and up were linked to a 27% higher Alzheimer’s risk, and exposure to railway noise of 50 dB was associated with a 24% higher risk of Alzheimer’s. Curiously, only car traffic noises were found to correlate with vascular dementia.

For just the year 2017, researchers estimate that out of 8,475 registered dementia cases in Denmark, traffic noise may be attributed to 1,216! 

How could a few car honks or screeching breaks lead to a condition as serious as dementia? Study authors can’t say for sure but speculate that consistently being exposed to unwanted sounds can lead to serious upticks in stress, sleeping problems, immune system changes, and increased bodily inflammation. All of those developments may influence dementia and cognitive outcomes.

All that being said, it’s critical to note that these findings are ultimately observational in nature. That means a direct causal relationship can not be established, at least not yet. More research on this topic is needed before any definitive conclusions can be agreed upon. Still, this work makes a compelling argument that traffic noise pollution is indeed linked to increased dementia risk, especially considering its long follow-up time and large population sample.

“If these findings are confirmed in future studies, they might have a large effect on the estimation of the burden of disease and healthcare costs attributed to transportation noise. Expanding our knowledge on the harmful effects of noise on health is essential for setting priorities and implementing effective policies and public health strategies focused on the prevention and control of diseases, including dementia,” the study concludes.

The full study can be found here, published in the British Medical Journal.

Read more dementia here.