A new study combining mobile apps, big data, and math modeling of sleep patterns around the world has analyzed the roles of biology and society in the setting of sleep schedules.
Led by mathematicians out of the University of Michigan, this study utilized a smartphone application at no charge that would reduce jetlag in order to obtain sleep data from people in 100 different nations; thousands of people were analyzed. Scientists looked at the impact of gender, age, and light exposure to the home country on the amount of sleep people get, along with the time they go to bed and the time they wake up.
Their findings showed that there are cultural pressures that can interfere with the natural circadian rhythm, which were most notable at bedtimes. Researchers note that morning responsibilities such as kids, school, and work do play a role in wake time, though it is not the only component. The trends at the population level indicate the expected outcomes of sleep patterns based on current knowledge of the circadian rhythms.
One of the researchers who was part of the study, Daniel Forger, a mathematician, stated that it is apparent in their findings that society governs bedtimes and the internal clock governs wake times, in which a later bedtime contributes heavily to sleep loss. Further, there was a strong effect on wake time from peoples’ biological clocks, and that is not referring to their alarm clocks. It is believed that these findings will help quantify the differences and similarities between social and solar timekeeping.
When discussing biological or internal clocks, Forger is referring to the circadian rhythm, or sleep-wake cycle. It is in reference to the bodily fluctuations in function and behavior that are linked to the 24–hour day. As mentioned in previous studies, these rhythms are managed by clusters of more than 20,000 neurons located behind the eyes, which are regulated by sunlight.
It has long been understood that circadian rhythms are the primary drivers of sleep schedules, even since the invention of 9-5 workdays and artificial light. This new research will help identify the role of society in these schedules.
Mr. Forger and his colleague, Olivia Walch, got together several years ago and released a smartphone application, Entrain, which assists traveling individuals in adjusting to new time zones and avoiding jet lag. This app makes custom schedule recommendations based on light and darkness time. In order to use the application, the user would need to enter their usual hours of sleep and light exposure, after which they are given an option to submit anonymously to the University of Michigan for study.
Naturally, the quality of recommendations depended greatly on the truth and accuracy of the individual’s information. Researchers believe that the people who were more motivated to get over jetlag quickly were more careful in their reporting of sleep habits and history.
Thousands of people submitted their information to U-M, which was further analyzed for patterns. Recognized correlations were put to the test in a circadian rhythm simulator, which is a mathematical model based on the knowledge of how light affects the brain’s SCN (suprachiasmatic nucleus). This is where the 20,000+ neurons reside. This model allowed researchers to dial the sun at will in order to find the correlations in extreme conditions.
Ms. Walch does note, however, that sleep patterns and bedtimes don’t respond the same way in the real world as they do in the model, as the model is missing the society component.
National averages of sleep time ranged between 7 hours and 24 minutes in Singapore to a maximum of 8 hours and 12 minutes in the Netherlands. This is not a large window of time; however, researchers make note that every 30 minutes of sleep makes a difference in cognitive functioning and long-term overall health.
There is an important lever for sleep-deprived people in these findings, the researchers state. The CDC has noted that one in three American adults are not getting the recommended 7 hours of sleep every night. Additionally, they note that sleep deprivation puts one at risk of developing health problems like high blood pressure, obesity, heart disease, stroke, stress, and diabetes.
In addition to the above, researchers at U-M also found that:
- Men in middle age got the least amount of sleep, usually fewer than 7 to 8 hours
- Women tend to schedule their sleep more than men, on average about a half hour more. Generally, they go to bed earlier and wake up later, and it is more often seen in women between the ages of 30 and 60.
- Individuals who spend time outside in sunlight everyday go to bed earlier than those who stay indoors most of the day.
- Those over 55 were more prone to schedule their sleep than those under 30. This could be due to a narrowed window that older people can fall asleep and stay asleep.
Sleep is vital to health and well-being, more so than most people realize, the researchers state. Even six hours a night puts one at risk of developing a serious sleep debt.
It does not take long to develop a sleep debt and begin to see functional decline. Being overly tired gives a feeling of drowsiness and inability to concentrate, which can be terrifying for some people, especially if they think they’re performing tasks to their best ability. Performance levels drop, but perception of performance goes unaltered.
This work demonstrates that smartphone technology can be a reliable source for gathering a great deal of information to study at a very low cost.
Author: Rachael Herman is a professional writer with an extensive background in medical writing, research, and language development. Her hobbies include hiking in the Rockies, cooking, and reading.