A recent study published in the journal Alzheimer’s & Dementia has found that long-term exposure to air pollution significantly increases the risk of dementia. The research, conducted in Denmark, also explored the potential role of noise pollution but found that air pollution is the primary factor contributing to dementia risk. These findings highlight the broader impacts of air pollution beyond respiratory and cardiovascular health, showing its detrimental effects on brain health.
Dementia, a condition characterized by progressive memory loss and cognitive decline, is a growing concern worldwide. With the global population aging, the number of dementia cases is expected to rise dramatically, from 60 million in 2019 to 150 million by 2050. Despite advances in medical treatments, there is no definitive cure for dementia, making the identification of preventable risk factors crucial.
Recent research has suggested that environmental factors, such as air pollution, may contribute to the development of dementia. Air pollution, already known to cause cardiovascular and respiratory diseases, might also promote brain inflammation and accelerate cognitive decline. This study aimed to investigate these potential links in Denmark, a country with relatively low but still significant air pollution levels.
The study followed a cohort of Danish nurses for 27 years, from 1993 to 2020, making it one of the longest and most detailed investigations of its kind. The researchers used historical data to estimate the nurses’ exposure to air pollution over 41 years, from 1979 to 2020. They also collected extensive information on the participants’ lifestyles and socioeconomic status.
The sample consisted of female nurses over the age of 44 in 1993, with additional nurses added in 1999. A total of 28,731 nurses were initially included, although those with pre-existing dementia or missing data were excluded, resulting in a final sample of 25,233 nurses. The researchers tracked these participants using national health registers to identify cases of dementia.
The study found that long-term exposure to various air pollutants, including particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2), and black carbon (BC), was associated with an increased risk of dementia. For example, the risk of developing dementia increased by 35% per 2.61 micrograms per cubic meter increase in PM2.5 levels. These associations remained significant even after adjusting for road traffic noise and other confounding factors.
Interestingly, the study also found that nurses with higher levels of physical activity had a lower risk of dementia when exposed to air pollution compared to their less active counterparts. This suggests that physical activity might help mitigate the adverse effects of air pollution on cognitive health.
However, the use of health registers to diagnose dementia might have led to underreporting or misclassification of cases, although previous studies have validated the accuracy of these registers. Additionally, the study only included female nurses, which limits the generalizability of the findings to other populations.
Future research should aim to include a more diverse sample, including men and individuals from different occupational backgrounds. It would also be beneficial to explore the effects of other environmental factors, such as occupational and leisure-time noise, and to investigate the potential interactions between various pollutants.
Moreover, further studies should examine the mechanisms through which air pollution affects the brain. Understanding these pathways could lead to the development of targeted interventions to prevent or reduce the risk of dementia associated with air pollution.
Despite these limitations, the study provides strong evidence that long-term exposure to air pollution is a significant risk factor for dementia. The findings underscore the need for stringent air quality regulations and public health policies to reduce air pollution levels. Additionally, promoting physical activity could serve as a protective measure against the cognitive decline associated with air pollution.
The study, “Long-term exposure to air pollution and road traffic noise and incidence of dementia in the Danish Nurse Cohort,” was authored by Stéphane Tuffier, Jiawei Zhang, Marie Bergmann, Rina So, George Maria Napolitano, Thomas Cole-Hunter, Matija Maric, Sonja Antic, Jørgen Brandt, Matthias Ketzel, Steffen Loft, Youn-Hee Lim, and Zorana Jovanovic Andersen.