Moving towards the model of a city that never sleeps has a price: citizens will sleep less and worse. And we must not forget that sleep, often undervalued, is a fundamental physiological process to maintain good health. We know that if we don't get enough sleep, we end up getting sick.
And how much is enough? Well, it depends on age, but a healthy adult, on average, needs to sleep 7 to 9 hours a day. The figure increases when it comes to children, who may need from 9 to even 16 hours a day.
And when should you sleep? Well, as diurnal animals that we are, we sleep at night. With some variations, yes, due to the different chronotypes. There are people who tend to go to sleep and wake up later (the owl or evening types) and those who have a natural ability to get up early and go to sleep earlier (the lark or morning types).
Despite these individual differences, the night is the time that our physiology reserves for sleep. Over millions of years, we have evolved organizing our physiological processes thanks to the alternation between light and darkness. However, the nights have changed a lot since the use of electric light became widespread just a century and a half ago. The night is no longer dark in many urban environments. Light has allowed human beings, with eyes adapted to the day, to colonize the night, destroying its darkness and, as a consequence, extending their period of activity until untimely hours.
Artificial light at night is considered a pollutant in itself and leads to a series of health problems. First of all, it causes us to sleep less. There are already studies that show that adults and the elderly tend to sleep less the higher the level of artificial light in the environment at night. It has also been observed that artificial light at night, both outdoors and indoors, can increase sleep problems by 22%. This light is the enemy of sleep because it confuses the clock that regulates it: it tells it that it is daytime and that it is not yet time to sleep.
Light pollution not only reduces sleep hours (which would be serious in itself), but excessive use of artificial light at night can have other serious health consequences. Among them, a greater probability of suffering from cardiovascular and metabolic disorders (obesity or diabetes), mental health disorders or even some types of cancer, such as breast, prostate or colorectal cancer, has been described. Controlled laboratory studies leave no doubt about the harmfulness of artificial light at night.
However, in epidemiological terms, there is still controversy due to the disparity in results. It is due, above all, to the so-called confounding factors: circumstances specific to the most illuminated areas that prevent us from discriminating which damages are due to night light and which are due to other factors.
One of those confusing factors is precisely noise, another sleep thief. Being able to colonize the darkness thanks to electric light has made the nights noisy, depriving us of the silence necessary to fall and maintain sleep. The noise that sneaks into our home harms us at any time of the day, whether it “bothers” us or not. But if it is at night, it also interferes with our sleep.
According to the European Environment Agency, prolonged exposure to environmental noise contributes to 48,000 new cases of heart disease and 12,000 premature deaths each year in Europe. In addition, 22 million people suffer from chronic discomfort and 6.5 million suffer from major chronic sleep disorders. It is estimated that one million years of healthy life are lost each year due to the effects of noise, including ischemic heart disease and sleep disorders. The latter account for the majority of the noise-related disease burden.
The negative consequences of road traffic noise are widely demonstrated. However, at night in cities there are other sources of noise that cause discomfort. One of the most important is nightlife. In fact, leisure noise maps are already being drawn up in several Spanish cities, although corrective measures are often insufficient.
In addition, the noise generated by leisure is increasing due to the increase in terraces, especially as a result of the covid-19 pandemic. For example, tables have increased 62% more than in 2019 in Barcelona and 5,700 new tables have been added in Madrid, now rising to 60,912. In smaller cities like Murcia the increase has been greater, with 75%, going from 400 terraces in 2019 to almost 700 currently.
Street cleaning, often carried out at night until the wee hours of the morning or early in the day, poses an added problem. Paradoxically, we could say that cleaning the streets at night interferes with the cleaning that sleep sets in motion in our brain through the glymphatic system.
Many of the problems that make it difficult to sleep could be solved with greater awareness and empathy on the part of citizens. But, in addition, we need an adequate legal framework and, above all, for the authorities to effectively ensure compliance.
In addition to national noise regulations, there are municipal ordinances that regulate different aspects that influence noise. How could a city council help its citizens sleep better? To begin with, we must start from the premise that sleep, due to its close connection with health, should always prevail over other aspects such as leisure. Therefore, some ideas would be the following:
And finally, the most important thing: understand, both at an institutional and individual level, that to build a healthier society it is essential to protect an environment that facilitates our sleep and that of our neighbors.
Sleep and allow yourself to sleep well.
This article was originally published on The Conversation. María Ángeles Bonmatí Carrión is a CIBERFES postdoctoral researcher and collaborating professor at the University of Murcia (UMU)
