Human sleep patterns average around seven hours per night globally, defying common cultural assumptions that modern lifestyles have drastically shortened our natural rest compared to historical baselines, according to a comprehensive overview study published on August 25, in Brain Medicine. Researchers analyzing data across ethnology, history, and genetics found that adults in industrialized nations generally sleep between six and seven hours nightly, a duration remarkably similar to un-electrified indigenous populations studied in Tanzania, Namibia, and Bolivia
Challenging the Eight-Hour Industrial Formula
The review titled “The New Science of Sleep,” authored by seven international researchers, examined long-held beliefs about human sleep duration and structure. The strict industrial formula dividing a 24-hour day into eight hours of work, eight hours of recreation, and eight hours of sleep lacks systematic historical backing, according to the study. Early survey data often cited from a 1913 Stanford University study actually focused exclusively on children and adolescents, distorting perceptions of historical adult norms. When examining isolated indigenous groups living without electricity or artificial illumination, researchers recorded average sleep durations ranging between 6.4 and 7.1 hours per day
From Edison’s Bulb to the Blue Light of Smartphones
While total sleep duration has remained relatively stable over centuries, the timing and regularity of rest have shifted significantly. The invention of the incandescent light bulb by Thomas Edison in 1878 expanded waking hours, establishing a cultural framework that often viewed extended sleep as unproductive. Today, contemporary society operates under 24-hour economic demands and digital connectivity. According to the study, the primary disruption stems from irregular sleep schedules and evening exposure to short-wavelength blue light emitted by smartphones and electronic devices last thing at night and first thing in the morning, which impairs sleep quality
Reassessing the Myth of Segmented Midnight Rest
The review also addresses historical claims regarding segmented or “divided sleep.” In 2001, U.S. historian Robert Ekirch popularized the theory that humans naturally woke up for an hour or two around midnight during the preindustrial era to pray, work, or socialize. However, the authors of “The New Science of Sleep” point out that historical documentation provides insufficient evidence for segmented sleep as a universal biological norm. Mentions of a “first sleep” in ancient and medieval texts lack consistent clinical backing, and premodern indigenous populations do not practice or prefer a biphasic nightly rest pattern, rendering it an exception rather than a biological rule
The DEC2 Mutation and Individual Genetic Needs
Individual differences in sleep needs are heavily influenced by genetics, specifically through regulatory genes such as DEC2. A rare mutation in this gene can safely reduce the biological need for sleep, as demonstrated in a 2009 study of a family where members function fully on six hours of sleep without daytime fatigue or cognitive impairment. Laboratory mice engineered with the same genetic mutation exhibited no behavioral deficits. Consequently, the study authors advise against pathologizing individuals who naturally thrive on roughly six hours of rest per night