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Luchtvervuiling ook slecht voor hersenen*
Uit een Amerikaanse studie, weliswaar met muizen, blijkt dat luchtvervuiling niet alleen slecht is voor uw longen en hart doch ook slecht kan zijn voor uw hersenen. Bij muizen die zes uur per dag vervuilde lucht inademde bleken dendrieten (vertakte uitlopers van zenuwcellen) in de hippocampus duidelijke veranderingen te vertonen. Het aantal werd minder, ze werden kleiner en er waren minder verbindingen. Hierdoor bleken die muizen na zes maanden ook duidelijk geheugen en cognitieve problemen. De resultaten waren zo duidelijk dat de onderzoekers verklaarden dat ook mensen moeten oppassen met (te lange) blootstelling aan vervuilde lucht.
Air pollution causes harmful physical changes in the brain
No one likes breathing polluted air. Exhaust fumes and particulate matter hanging in the air can make you cough and give you a headache. Now comes information from another Ohio State University study that long-term exposure to air pollution can literally change your brain. And as you might expect, these physical changes in the brain are not beneficial. They are associated with learning and memory problems and even depression.
The new study, just published online in the journal Molecular Psychiatry is the first long-term research to show the negative impact of air pollution on the brain, according to Laura Fonken, lead author of the study and a doctoral student in neuroscience at Ohio State University. "The results suggest prolonged exposure to polluted air can have visible, negative effects on the brain, which can lead to a variety of health problems," Fonken said in a statement to the media.
In earlier studies in mice, researchers in Ohio State University's Davis Heart and Lung Research Institute (who also collaborated with Fonken and colleagues on the new research project) found that fine air particulate matter causes widespread inflammation in the body -- leading to a heightened risk for diabetes and obesity, as well as hypertension. Their extended research on air pollution's impact on the brain adds more disturbing evidence that bad air is bad for thinking, too.
"The more we learn about the health effects of prolonged exposure to air pollution, the more reasons there are to be concerned," stated Randy Nelson, co-author of the study and professor of neuroscience and psychology at Ohio State, in the press statement.
For the new study, lab mice were exposed five days a week to either filtered air or polluted air for six hours a day. The polluted air contained the same type of pollution created by cars, factories and natural dust and included very fine particulate matter -- particles so minute they are only about 1/30th of the average width of a human hair. Because of their small size, these particles can be inhaled deeply into the lungs and end up in other organs of the body.
The mice were exposed to an amount of polluted air equivalent to what people are exposed to in some polluted urban areas, according to the researchers. Then various behavioral tests were performed on the rodents after the animals spent 10 months regularly breathing either filtered or polluted air.
The results showed severe impairments in memory and learning in the pollution exposed animals. And mice exposed to the polluted air exhibited more depressive-like behaviors than did the mice that breathed the clean air. In addition, the polluted-air breathing mice showed signs of higher levels of anxiety-like behaviors in one specific test, but not in another.
So how could air pollution trigger changes in learning, memory and mood? To find out, the scientists focused on the hippocampus, the area of the brain associated with learning, memory and depression.
The results? The researchers found undeniable physical differences in the hippocampi of the mice who were exposed to polluted air compared to the animals who breathed clean air. Specifically, neurons (nerve cells) known as dendrites were clearly changed. Normally, dendrites have small projections growing off them, dubbed spines, which transmit signals from one neuron to another. But in the mice exposed to polluted air, there were shorter dendrites, fewer dendrite spikes and, overall, a reduction in the complexity of brain cells. And earlier research has shown that these types of changes are linked to decreased learning and memory abilities.
The research team found evidence that low-grade inflammation was evident in the hippocampus in the pollution exposed mice. That could have caused the brain changes. Inflammation-causing chemical messengers in the immune system known as cytokines were found to be more active in the hippocampus in the animals who breathed the polluted air.
"The hippocampus is particularly sensitive to damage caused by inflammation," Fonken said in the media statement. "We suspect that the systemic inflammation caused by breathing polluted air is being communicated to the central nervous system."
Although the new study involved mice and not humans, the scientists think the findings have profound implications for people exposed regularly to air pollution. "This could have important and troubling implications for people who live and work in polluted urban areas around the world," Fonken concluded. (December 2011)