Are humans sleeping less nowadays? Many of us might quickly reply with a resounding ‘yes’. But even if it’s true for you is it true for most? It’s more contentious than you think.
Yes, you’ll find a lot of surveys showing a clear decline in sleep from the mid-20th century to the 2000s (when people started using a lot of digital devices). For instance, Gallup found that in 1942, 59% of Americans slept eight hours or more nightly (with only 3% sleeping less than 5 hours), but by 1990 only 27% slept more than 8 hours while 14% were getting less than 5 hours.
But these are self-reports. A 2015 review of 168 studies from 1960–2013 found no significant decline in adults’ objectively measured sleep duration over that 50+ year span. In fact, we’re sleeping a lot longer (on average) than we think.
More Sleep Than You Thought
What’s more intriguing is that even if we suppose people today sleep less than they did a few decades ago, overall it seems that those of us who grew up in an industrial society sleep much more than our ancestors. A 2015 study, for instance, measured the actual sleep patterns (as opposed to self-reports) of hunter-gatherers in Tanzania, Namibia, and Bolivia. It found tribespeople slept between five hours 40 minutes and seven hours six minutes on average a night.
Now, a recent review of 54 population-level sleep studies came to a surprising conclusion. It suggests people in industrial societies are likely sleeping longer compared to ancient ancestors while also experiencing a profound disruption in their sleep cycle. Specifically, we have disrupted circadian rhythms — the internal clocks that govern everything from hormone release to metabolism.
In other words, we’re seeing a trade-off. Industrial societies have created environments that allow for longer, more efficient sleep. But at the same time, they’ve weakened our connection to the natural cycles of light and darkness that have shaped human biology for millennia.
The Sleep Paradox: Longer, But Less Natural
The study, led by David Ryan Samson and Leela McKinnon, both anthropologists at the University of Toronto, analyzed sleep data from 54 populations around the world, ranging from hunter-gatherers in Tanzania to urban dwellers in the United States. Using advanced tracking technologies like actigraphy — a method that measures movement to infer sleep patterns — the researchers compared sleep duration, efficiency, and circadian function across these diverse groups.
The results might surprise you. People in industrial societies slept an average of 7.1 hours per night, compared to just 6.4 hours in non-industrial societies. Sleep efficiency — the percentage of time spent actually sleeping while in bed — was also higher in industrial populations, at 87.9% versus 73.9% in non-industrial groups.
But when it came to circadian function, the tables turned. Non-industrial societies, with their exposure to natural light and temperature fluctuations, showed stronger circadian rhythms. Their bodies were more in sync with the 24-hour cycle of day and night. In contrast, industrial societies, with their artificial lighting and climate-controlled environments, exhibited weaker circadian function.
Our bodies evolved in environments where light and temperature were the primary cues for sleep and wakefulness. Now, we’ve created environments that override those cues, and our circadian rhythms may be paying the price.
“Everyone I talk to in Canada and the US talks about how awful their sleep is,” McKinnon told New Scientist. “The numbers aren’t showing that.”
The Hidden Cost of Modern Sleep
The implications of this circadian disruption are profound. Research has linked weakened circadian rhythms to a host of health problems, including depression, obesity, and even an increased risk of dementia. Circadian misalignment doesn’t just affect sleep — it affects every system in the body.
The main takeaway from this study though is that the popular narrative that modern life is causing a global sleep crisis may be wrong. While it’s true that many people report feeling sleep-deprived, the data suggest that, on average, industrial societies are actually sleeping more than their non-industrial counterparts. The real issue, according to the researchers, may be the quality of that sleep — and the misalignment of our internal clocks.
So, what can be done? The researchers suggest that improving “chronohygiene” — the practice of aligning daily routines with natural circadian rhythms — could help. This might involve spending more time outdoors, reducing exposure to artificial light at night, and maintaining consistent sleep schedules.
No one’s saying that industrial societies should abandon electricity or modern conveniences. But we do need to find ways to reconnect with the natural rhythms that our bodies are designed to follow. It’s a shift in mindset from getting more sleep to getting the right kind of sleep.
