Why some insomnia may just be our ancestors calling
Industrialisation killed sleep by giving people electric lighting, late-night television shows and an ever-dwindling number of hours of sleep. Or so the story goes.
In reality, and despite the distracting glow of cellphone screens, modern humans are getting two-and-a-half hours more sleep than their ancestors.
Studies of hunter-gatherer groups such as the San show they sleep six-and-a-half hours a night. But they don’t have the sleep hang-ups of city slickers, such as insomnia.
Now researchers believe that understanding how people in pre-industrial societies sleep may help others get a good night’s rest without popping sleeping pills.
Prof Paul Manger of the School of Anatomical Sciences at the University of the Witwatersrand studies animal brains, in part to understand the peculiarities of sleep. He was part of a team that discovered that duckbilled platypuses have 80% of their sleep as rapid eye movement (REM) sleep. Humans have about 20%.
They also found that elephants in the wild catnap about two hours a night and that the smaller the animal, the more they are likely to sleep. The record holder for most sleep in mammals is the little brown bat, at 18 hours a day.
Manger participated in a large study that examined the sleep patterns of three hunter-gather groups: the Hadza of Tanzania, the San of Namibia and the Tsimane of Bolivia.
They studied the San by asking them to wear sleep trackers. "One thing we found out about the San is that they don’t go to sleep when the sun sets, they go to bed two to three hours later," he says. "They are then up well before sunrise."
The team discovered that their subjects didn’t sleep during the day. "These are very busy people," says Manger.
The San did not appear to suffer from insomnia.
After studying humans and animals, Manger thinks the sleep switch has been discovered. It is not the amount of light or dark, but the weather.
"What seems to be really telling animals [and humans] when to go to sleep and when to wake up is weather parameters, and it looks like it is a combination of temperature and humidity. What time we fall asleep is when the weather feels right," he explains.
If the research is correct, this could change the way science approaches sleep therapy.
"People have a whole lot of different ideas on sleep therapy — you have to do this and you have to do that to get a good night’s sleep — but maybe it is more about controlling the sleeping environment and mimicking these natural variations in temperature and humidity," Manger says.
South African Society of Sleep Medicine chairman Dr Jeff King sees a lot of the nation’s sleep problems.
One of the biggest challenges South Africans share with the western world is the effect of obesity on sleep. Abdominal fat prevents the diaphragm from moving properly, causing decreased oxygenation, which influences sleep. Stress also leads to insomnia.
King says a lack of sleep is a killer, bringing on high blood pressure and causing increased deaths on the roads.
One of the types of sleeplessness King comes across is when the sufferer wakes up in the middle of the night after just two or three hours of sleep. But while some regard this as a type of insomnia, others believe it is simply going back to the way humans used to slumber.
History professor Roger Ekirch of Virginia Tech in the US has been studying the phenomenon of segmented sleep for 30 years. He believes this is the way humans slept before the Industrial Revolution.
People who suffer from middle-of-the-night insomnia should take some consolation from the fact that their sleep is not necessarily abnormalRoger Ekirch
Most divided their nights into two sleeps. The first sleep usually began about two hours after dusk. After a couple of hours, people would wake up, stay awake for an hour or two and then go back to sleep until just before dawn.
After they woke up during the night, people would leave their beds, pray, visit their neighbours or have sex. It was regarded as a period of heightened creativity.
"People waking from their first sleep awoke from a dream," says Ekirch. He has found more than 500 references to segmented sleep from diaries and court reports. There is a reference to it in Homer’s Odyssey.
Ekirch says the practice of two sleeps a night was killed by artificial light and changing beliefs about a good night’s rest. The Early Rise Movement in the 1830s preached that a productive member of society needed a single, long sleep.
"By the 1830s, people’s first sleep starts to expand, by the 19th century, the first sleep ends close to dawn," he says.
At the dawn of the 20th century, the two sleeps are a thing of the past in many industrialised countries. Ekirch found one of the last written references to it in SA in a court record.
"I found court records that told how a wife wanted to murder her husband and set their hut on fire," he explains.
"The judge explains to the other judges that the incident took place, according to the wife, after their first sleep."
While most people strive for eight full hours of sleep each night, segmented sleep is wired into human brains and sometimes makes an appearance, Ekirch says. When it does, it shouldn’t be regarded as an unhealthy way of sleeping.
"People who suffer from middle-of-the-night insomnia should take some consolation from the fact that their sleep is not necessarily abnormal."