Easy access to electricity and artificial light triggers a measurable reduction in human sleep, suggests a new study conducted at the University of Washington. The research comparing traditional hunter-gatherer living conditions to a more modern setting, is the first study to document this relationship in the field.
Lead author Horacio de la Iglesia said that everything they found feeds what they had predicted from laboratory or intervention studies, where researchers manipulate certain aspects of light exposure, but this is the first time they saw this holds true in a natural setting.
The researchers compared two traditionally hunter-gatherer communities that have almost identical ethnic and sociocultural backgrounds, but differ in one key aspect - access to electricity.
They wanted to see if, all other factors aside, electricity would impact people's sleep during an average week in both the summer and winter. They found this rare scenario in northeastern Argentina, with two Toba/Qom indigenous communities living about 50 kilometers (31 miles) apart.
The first has 24-hour free access to electricity and can turn on lights at any time, while the second has no electricity, relying only on natural light. In their usual daily routines, the community with electricity slept about an hour less than their counterparts with no electricity.
These shorter nights were mostly due to people who had the option to turn on lights and go to bed later, the researchers found. Both communities slept longer in the winter and for fewer hours in the summer.
These findings suggest there's a biological driver in humans that requires more sleep in the darker winter months. They also plan to study the effects the moon cycle may have on sleep patterns. The study is published online in the Journal of Biological Rhythms