Dementia: Traffic noise may raise risk

Modifiable risk factors for dementia are receiving growing attention.
Researchers have linked noise pollution to several adverse health conditions.
A Danish study shows a possible link between transportation noise and an increased risk of various forms of dementia, especially Alzheimer’s disease.
More than 55 millionTrusted Source people worldwide have some form of dementia, according to the World Health Organization (WHO). As the global population ages, experts expect this number to exceed 150 million by 2050.

Modifiable risk factors for dementia
Identifying potentially modifiable risk factors for dementia is essential to prevent and manage this growing global health crisis.

Now, a new Danish study that appears in the journal The BMJTrusted Source suggests that having exposure to traffic noise results in a higher risk of developing all-cause dementia, especially Alzheimer’s disease.

Numerous studies have consistently linked noise pollution to various health conditionsTrusted Source, such as obesity, diabetes, and coronary heart disease. However, there is scarce research into the effects of noise on dementia.

Recognizing the need for more controlled testing, the researchers investigated a potential association between long-term residential exposure to transportation noise and the risk of incident dementia.

Transportation noise is the second worst environmental risk factor for public health in Europe, after air pollution. Around 20% of people in Europe have exposure to transportation noise above the recommended 55-decibel level.

Effects of disrupted sleep
Having exposure to this level of noise during the night is especially concerning, as sleep is a critical period for mental and cognitive restoration.

Experimental studies suggest that fragmented sleep resulting from noise disturbance is associated with increased oxidative stress, alterations in the immune system, and increased systemic inflammation. Experts regard all these conditions as early events in the onset of dementia and Alzheimer’s disease.

The new study included nearly 2 million adults, aged 60 years or older, who lived in Denmark between 2004 and 2017. The researchers estimated exposure to road traffic and railway noise for all participants’ residential addresses and focused on the buildings’ most and least exposed sides.

The team used Denmark’s high quality national health registers to identify cases of all-cause dementia and other types of dementia reported during an 8.5-year span. These conditions included Alzheimer’s disease, vascular dementia, and Parkinson’s disease.

Over 103,000 new cases of dementia occurred during this time. Further analysis of the study data found noise from road traffic and railways to be associated with a higher risk of all forms of dementia, notably Alzheimer’s disease.

Several animal studies indicate that having continual exposure to noise activates the formation of key genes that potentially lead to the neuropathological changesTrusted Source related to Alzheimer’s disease in the hippocampi of mice.