First Danish study into air pollution and cognitive decline

Researchers in Denmark have used high quality cohort data to draw a link between poor air quality and the onset of dementia

The study followed a cohort of 25,233 nurses for 27 years, between 1993 and 2020. The team, from the University of Copenhagen, estimated air pollution and road traffic noise levels at the nurses’ home addresses and examined their associations with dementia.

Traffic noise was considered as a potential cause of dementia because previous research has shown it to increase the risk of cardiovascular disease and possibly psychiatric disorders. Furthermore, air pollution is obviously linked to road traffic. 

The Danish Nurse Cohort was originally designed to study the effects of hormone replacement therapy in menopausal women and is rich in data.

Research Assistant from Section of Environmental Health Stéphane Tuffier said of the depth of information at their disposal: ‘This is internationally unique and necessary in regards of the development of dementia which can take many years. Second, the air pollution was estimated for each participant for a total of 41 years, which is also incredible. Third, we had extensive details about participant’s lifestyle and socio-economics and all our result take them in consideration. The novelty of this study is the very detailed and accurate data that we used.’

1,409 of the nurses were diagnosed with dementia, the median age of onset being 79.1 years. These nurses tended to live in urban areas compared to nurses free of dementia.

The research found a clear link between long-term exposure to pollutants and incidence of dementia: ‘We found that these associations were independent of road traffic noise, whereas the weak association of road traffic noise with dementia diminished after adjusting for air pollution.’

Tuffier added: ‘Nurses with higher physical activity had a lower risk of dementia when exposed to air pollution compared to nurses with less physical activity. This indicates that physical activity might mitigate the adverse effects of air pollution on cognitive decline and risk of dementia.’

 Professor at Section of Environmental Health Zorana Jovanovic Andersen said: ‘This is the first study in Denmark showing a link between air pollution and dementia. Although air pollution levels in Denmark have been declining and are relatively low, compared of the rest of Europe and world, this study shows that there are still significant and concerning health effects that demand more action and policies towards reduction of air pollution.

‘As we are going to live longer, and more and more people will be diagnosed with dementia, this finding is important as it offer an opportunity to prevent new dementia cases, and ensure more healthy aging, by cleaning up the air we breathe.’

The full research can be read here.