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Friday, November 16, 2018

In findings published on Thursday in Current Biology, a team of researchers reported weekly and seasonal changes in sleep patterns in the United States are influenced by social schedules more than by length of the day. Without using monitors and questionnaires, data were here collected using a review of two years of the publicly viewable geographically tagged Tweets from about 240,000 users.

In this study, the researchers compared sleep patterns against both natural phenomena, like day length, and social factors, like the school year, in the U.S. population.

Researchers described analyzing messages from 1500 counties stretching from the east to west coasts of the mainland United States during 2012 and 2013. The data was collected in 15 minute periods. The geographic tags allowed the researchers know each user’s location and to correlate these messages with time zones. The use of Twitter also allowed for a large study population.

By comparing their survey findings to existing surveys, the researchers were able to establish that periods with low levels of Twitter activity could be equated with time spent asleep. This showed that people slept and rose later on weekends than during the work week, a phenomenon called “social jet lag.”

The authors also observed an association between what they dubbed “Twitter social jet lag” and the school year. The study population showed the most social jet lag in February and the least in June and July, which matched local school schedules. The researchers also found public holidays and other times when school was cancelled to be associated with less social jet lag. There was also a weaker but detectable correlation with the number of hours of natural daylight, the authors reported.

The results were consistent with similar studies performed in Germany and Estonia, showing that people’s sleep patterns have some relationship with daylight but a more pronounced relationship with social obligations. They were also consistent with some earlier studies showing a link between more social jet lag and health problems such as depression and obesity.

“For the limited number of counties with unified school schedules for which the calendars are readily available, social jet lag lines up almost perfectly with the calendars, even though the population of Twitter users is clearly not just students,” reported co-author Michael Rust of the University of Chicago. “This is consistent with some studies that suggest that the effect of the sun on our lives may be getting weaker over time, perhaps as we spend more time indoors looking at our phones.”

“This study is indicative of the amazing amount of data that’s out there,” says Ludwig Maximilian University of Munich sleep scientist Martha Merrow, who was not one of the authors. “It shows the power of social media in revealing aspects of human behavior to us.”

Rust also reports that this study left him “thinking about ways” to educate the public about their own circadian clocks and their effects on their lives and health.

The researchers referred to their own findings as “Twitter social jet lag.” The researchers called the overall picture of the country’s Twitter patterns a “tweetogram,” after “actogram,” which means a log of general activity.

The study was funded by the U.S. National Institutes of Health.

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