Comparison between an African town and a neighbouring village shows delayed, but not decreased, sleep during the early stages of urbanisation

TLDR

Sleep deprivation is linked to negative health outcomes, and electricity may allow later bedtimes without extending sleep, prompting study of pre‑industrial‑style communities. The study compares sleep and activity patterns between an urban town and a rural village in Mozambique during early urbanisation. Sleep and activity were measured in Milange and Tengua, capturing bedtimes, light exposure, and sleep quality. Milange had later bedtimes (~1 h) with more evening light and less daytime light, yet similar sleep duration to Tengua, while Tengua’s poorer sleep quality was associated with rural attributes, indicating that electricity delays sleep timing but urbanisation improves sleep quality.

Abstract

The well-established negative health outcomes of sleep deprivation, and the suggestion that availability of electricity may enable later bed times without compensating sleep extension in the morning, have stimulated interest in studying communities whose sleep pattern may resemble a pre-industrial state. Here, we describe sleep and activity in two neighbouring communities, one urban (Milange) and one rural (Tengua), in a region of Mozambique where urbanisation is an ongoing process. The two communities differ in the amount and timing of daily activity and of light exposure, with later bedtimes (≈1 h) associated with more evening and less daytime light exposure seen in the town of Milange. In contrast to previous reports comparing communities with and without electricity, sleep duration did not differ between Milange (7.28 h) and Tengua (7.23 h). Notably, calculated sleep quality was significantly poorer in rural Tengua than in Milange, and poor sleep quality was associated with a number of attributes more characteristic of rural areas, including more intense physical labour and less comfortable sleeping arrangements. Thus, whilst our data support the hypothesis that access to electricity delays sleep timing, the higher sleep quality in the urban population also suggests that some aspects of industrialisation are beneficial to sleep.