On 30 March, Dr Giulia Grande and colleagues published a paper in JAMA Neurology, identifying an association between long-term exposure to air pollution and an increased risk of dementia. Having a cardiovascular disease diagnosis amplified this association, with heart failure and ischemic heart disease enhancing the dementia risk.
Recent evidence from clinical studies points to a link between air pollution and diseases associated with ageing. A 2015 Lancet article which analysed data from global epidemiological studies revealed that ambient, particulate air pollution (which is produced when burning household fuels, for example) might contribute to over 17% of ischemic heart disease cases and 16.5% of lung cancer cases. In addition, studies indicate that high levels of pollutants in the air might be linked with faster cognitive decline in older individuals.
To verify whether the association between air pollution and dementia, and to identify any health-related cofactors that may modify this association, Dr Grande and colleagues used longitudinal data from the SNAC-K study (Swedish National Study on Aging and Care in Kungsholmen). The SNAC-K longitudinal study recruited Stockholm-based participants aged over 60 years between 2001 and 2004, following them up until 2013. All 2927 participants resided in the same district in central Stockholm, Kungsholmen. Yearly air pollution levels were estimated by analyzing emission inventories compiled by the Swedish authorities, which were mapped to specific streets within the Kungsholmen district.
By referencing the SNAC-K longitudinal data to the air pollution levels (defined as particulate matter or nitrogen oxide) associated with the addresses of the individual participants, the researchers were able to identify a significant association between the amount of exposure to air pollution in the preceding 5-year period and dementia risk. Specifically, higher levels of particulate matter air pollution (PM) was associated with a 75% increased odds of dementia, while higher levels of nitrogen oxide were associated with a 66% increased odds of dementia. Both of these air pollution measures are linked to vehicle emissions and burning of fuels. Stratification analyses revealed that heart failure and ischemic heart disease enhanced the risk of dementia in individuals exposed to high air pollution levels, by 38% and 14% respectively. As well as highlighting the damaging effects of air pollution, these data underline the importance of optimizing the treatment of cardiovascular disease for older individuals living near roads in urban environments. The original article was published in JAMA Neurology and can be found here:
https://jamanetwork.com/journals/jamaneurology/fullarticle/2763459
