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 “It’s a really interesting finding and definitely suggests that air
pollution may be related to mental health,” said lead author Melinda
C. Power of Johns Hopkins University in Baltimore.
“If this is truly causal this is going to have a huge effect on the
population because everyone is exposed, but we need more research to
build this body of evidence,” Power added.
The researchers used data on more than 70,000 women in the Nurses’
Health Study who filled out an eight-question anxiety survey between
ages 57 and 85.
Overall, about 15 percent of the women had high anxiety symptoms.
Using their previous home addresses from before they filled out the
anxiety questionnaire, the researchers were able to estimate the
women’s exposure to so-called particulate matter in the air during
the past 15 years, based on factors like distance to major roadways,
population density, local sources of emissions and wind speeds.
The researchers found no link between anxiety levels and large air
pollution particles, but exposure to fine particles was tied to
increasing anxiety levels, according to results in BMJ. The more
recent the exposure, the higher the level of anxiety tended to be.
For example, women who were exposed to the most small particles in
the air one month before their anxiety test were about 12 percent
more likely to have high anxiety symptoms, compared to those
estimated to be exposed to the least particles one month previously.
Fine particulates come from combustion sources, including cars and
power plants, Power told Reuters Health by phone. The smaller the
particle, the deeper it may travel into the lungs.
“Our study can only comment on the population level, on average
people who were more highly exposed had a higher level of anxiety,”
she said. It did not assess distance to pollution sources or the
amount of air pollution an individual would need to experience to
have increased anxiety.
Since it was an observational study, it does not necessarily
indicate that pollution causes anxiety, she said. Women living in
more polluted areas may experience other sources of stress that
would be linked to anxiety as well.
The authors suspect that fine particulate pollution may be linked to
certain subtle conditions, like inflammation, which may increase the
risk of anxiety. Further research will need to explore this
possibility, and to look for a similar link among men and people of
a younger age, Power said.
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It is too soon to think about intervening or giving individuals
recommendations based on this result, she said.
However, there is substantial evidence that lowering air pollution
would improve cardiovascular health and respiratory health and
reduce the risk of stroke, she said. Short-term exposure to
particulate pollution is tied to an increase in stroke risk
according to an analysis of all published research on the subject,
which appears in the same issue of BMJ.
The relationship between atmospheric pollution and risk of heart
attack and heart failure had already been established, and this new
paper, supported by the British Heart Foundation, adds stroke risk
to that category, said lead author Dr. Anoop Shah of the University
of Edinburgh in the U.K.
There’s not much an individual can do to decrease their exposure to
air pollution as it's ubiquitous, Shah told Reuters Health by phone.
But policymakers do have the power to improve public transport
systems in urban areas and reduce the number of vehicles on the
roads, which are the major source of damaging pollution, he said.
In fact, as reported by Reuters today, Beijing has introduced
measures to limit the number of motorists on heavily polluted days.
It's the latest move by authorities there to battle the choking smog
that has blanketed the city in recent years.
SOURCES: http://bmj.co/1CDfX3q
and http://bmj.co/1GjHJUe BMJ, online March 24, 2015.
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