Longitudinal study of Toba/Qom communities reveals delay and shortening of sleep in real time.

While artificial light and digital technologies are widely assumed to delay and curtail sleep, direct, longitudinal evidence documenting these changes is remarkably scarce. From 2012 to 2024, we conducted a longitudinal study of native Toba/Qom communities in northern Argentina, including rural groups newly introduced to electricity and semi-urban groups with earlier access to electricity. Using linear mixed-effects models on a dataset of over 12,000 actigraphically recorded sleep events from 156 participants at different times, we observed striking shifts in sleep dynamics. Remarkably, both groups showed delays of close to 1 h in sleep timing, and participants from rural communities lost 35 min of sleep within the course of a decade. These changes occurred across a period that included, first, the introduction of electricity to rural communities after 2016, and, in more recent years, the spread of the internet and smartphone use among the Toba/Qom. While previous work in these and other populations has shown that both factors are associated with changes in sleep habits, our analyses suggest that they cannot fully explain the reported shifts in sleep timing across time by themselves, which may therefore be consistent with concurrent broader processes of modernization and acculturation. These transformations highlight the rapid changes that can take place in communities going through the early stages of the adoption of modern technologies, offering a contemporary parallel to the shifts in human sleep hypothesized to have accompanied global industrialization.