Pollution linked to stroke and anxiety

Bad air days correlate with higher anxiety levels and are also linked to strokes, new research has revealed.

The potential health consequences of exposure to airborne pollution have been highlighted for many years. The WHO attributes one death in every eight to air pollution, and other recent evidence suggests a role of pollution in the development of diabetes, pre-term birth risk and low birthweight.

Now two papers in the British Medical Journal this week add further weight to the argument, demonstrating a link to stroke risk and anxiety.

One of the studies combined the data from 103 independent other studies carried out in 28 countries and logged over 6 million data points. Bad air days, it concluded, are significantly associated with hospital admissions for stroke.

In a second study, which used data from over 70,000 nurses who have been followed up over a long period of time, pollution exposure was significantly linked to anxiety. Greater exposure to smaller pollutant particles, referred to as PM2.5, the team found, was associated with increased reported anxiety scores in the study subjects, an effect that remained even when effects such as stroke risk where controlled for.

The findings tally with previous observations showing an association between pollution and suicide risk. However, the researchers acknowledge in their BMJ report that there are some confounding variables, like noise, which may also be playing a role.People exposed to the greatest levels of pollution may be exposed to greater noise pollution too. That said, fine airborne pollutant particles have been shown to trigger inflammatory responses in the body, and it has been shown that systemic inflammation can lead to mood disorders including anxiety and depression.

The findings are therefore biologically plausible although, as an accompanying editorial emphasises, further study is warranted to establish and confirm how these links occur.