Don't be afraid of street lights
Insomnia caused by urban light turned out to be a myth
Denis Strigun, Naked Science
The prevalence of insomnia is often associated with urbanization. Thus, it is believed that artificial lighting sources characteristic of post-industrial society negatively affect the duration and quality of sleep. The experience of developing countries, however, calls this hypothesis into question. In particular, groups of hunters and gatherers from Africa and South America, who do not have access to electricity, sleep worse on average than residents of other areas. The reliability of such results remains low, since, say, a more labor-intensive lifestyle could affect them. Nevertheless, the coexistence of modern pre-industrial and developed societies is valuable for such comparisons.
The authors of the new article, experts from the UK, Brazil, Colombia, the USA and South Africa, tested the assumption on those living in the province of Zambezia in the Republic of Mozambique. Article Beale et al. Comparison between an African town and a neighboring village shows delayed, but not decreased, sleep during the early stages of urbanization published in the journal Scientific Reports.
A distinctive feature of the region is that industrialization continues in it: from 2002 to 2008, citizens' access to electricity increased from 18.7 to 34.8 percent, while only 7.4 percent of the population live in the urban part of the Milange district.
A picture from the University of Surrey press release
Urbanization and electricity are not to blame for sleep loss – VM.
The researchers recruited 62 residents of the latter and the non-electrified village of Tengua, located next door, aged 18 and over. At the first stage, the volunteers were interviewed about the quality, duration and conditions of sleep.
Then, for two weeks, the authors recorded objective parameters: during this period, respondents continuously wore a wrist actigraph with an accelerometer, temperature and light sensors. This made it possible to compare environmental factors (including infrared radiation) with mobility based on the time of day. The analysis showed that the activity modes of the villagers and the city are very different. The first had a peak in the morning and evening, when the heat subsided, and yet was tied to noon, so they were exposed to more light. The townspeople, in turn, were more active after sunset, and the subjective middle of the day lagged behind daylight by about 42 minutes.
Graph from an article in Scientific Reports
Although artificial light was present only in Milange, all volunteers went to bed much later than sunset. Meanwhile, the villagers went to bed an hour earlier – about 2.8 hours after nightfall – and woke up 30 minutes before the townspeople. It is curious that, despite the differences, the duration of sleep in both groups was almost the same, and its quality in the respondents from Tengua was even lower. In particular, their sleep was more restless, which was expressed in frequent awakenings and, as a result, increased nocturnal activity. The factors that explained the trend, scientists attributed the type of bed (mats in the latter) and the number of people in the dormitory – the villagers had it higher.
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24.07.2017