Sometimes evolution seems to play cruel tricks on us. Take our senses for example. Whilst our eyes have a beautifully simple mechanism to shut out the world, where are our ‘earlids’?
When unwelcome noise intrudes on our lives we have to find our own man-made solutions, or alternatively, put up with the din.
Our ears are a permanently open auditory channel, and this is true whether we’re we awake or asleep. But this constant vigilance -an adaptive trait, once useful for warning us of night-time predators – does not integrate well into the cacophony of 21st century inner city life.
Environmental noise, especially in urban settings is known to cause a range of physiological, psychological and cognitive disturbances. However, up until recently, little has been known about the long term health effects of sleeping in a permanently noisy environment.
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In the online blog of Scientific American, Dorian Rolston takes a look at the various ways that noise insidiously invades our sleep, sometimes with alarming results. He says that:
Even if brain arousals don’t jostle someone awake, they do disrupt sleep—in ways that, akin to the fight-or-flight response, are known to generate cardiovascular activation, such as increased heart rate and blood pressure.
With advances in sleep-monitoring technologies, scientists are beginning to realise that although we’ve adapted to living in cities, humans don’t seem to cope very well with sleeping in noisy urban environments:
Today, though, more sophisticated brain activity monitoring can detect consequences beyond diminished quality of life. A city’s soundscape appears to be setting off the body’s acute stress responses that raise blood pressure and heart rate, mobilizing a state of hyperarousal.
A 2011 report by the World Health Organisation looked at the serious effects that environmental noise has on public health. After examining numerous large scale epidemiological studies over the last 10 years, the report found that:
“preliminary results from a study of six European countries, included in the WHO publication, attributed to noise nearly 1 in 50 heart attacks across Western Europe. The panel ultimately ranked traffic noise second among environmental threats to public health, just behind air pollution, and affirmed the threat to be, unlike that from exposure to second-hand smoke, dioxins, or benzene, rising inexorably. Noise pollution “is considered not only an environmental nuisance,” WHO has warned correctively, “but also a threat to public health.”