I recently moved into a new place, but something went wrong with the air conditioning. My wife is very much used to air conditioning. She’s still having a difficult time with it since the AC hasn’t been fixed at the time of writing. Being originally from the Philippines, this isn’t new to me. However, at night it really hits – we have a loft-style bedroom, and thanks to convection, warm air rises and take a gooooood guess where all that warm air ends up.
From experience, we know that sleep is often associated with falling body temperatures, but we keep our blankets on us since it’s not exactly easy to fall asleep if it’s too cold, either. There are quite a few hacks that people use in order to sleep soundly, but we’re really trying just not to wake up in the middle of the night. Try it yourself (not on a weeknight – you really want to be a mess before work or class?) – try sleeping when you’re too warm. You can certainly try, but even if you manage to get a little shut-eye, you really don’t feel rested.
Now we cue up climate. People from the tropics (like me) are used to sleeping in higher temperatures, but we’ve got our own environmental controls like electric fans and maybe the way the house is built. Central air is rare and often a luxury. However, since climate change has introduced a host of weather-related issues, including increased temperatures over the summer or shorter winters/longer summers, one could find themselves struggling to sleep. Hey, even people with active nightlives need sleep too.
Using biostatistics on a huge sample set (765,000 American residents from 2002-2011), the study looks at relationship between increases in nighttime temperature and reports of insufficient sleep.
Obradovich et al. looked at a large data set provided by the Centers for Disease Control and Prevention (CDC), specifically the Behavioral Risk Factor Surveillance Survey (BRFSS). It’s a huge, publicly available data set that big data nerds can play with (statisticians suggest it’s good practice, too). Anyway, one particular question in the BRFSS was relevant: “During the past 30 days, for about how many days have you felt you did not get enough rest or sleep?” These were matched by location to data obtained from the National Centers for Environmental Information Global Historical Climatology Network – Daily (GHCN-D), another massive data set. Seriously, this study is just nerding out on big data. Once they have data, they can fit it on a line to see if there are any correlations between nighttime temperatures, lack of sleep, seasons, and maybe other variables that could give the line better predictive power. Man, this study is just nerding out with big data.
So what did the authors find from the massive data sets? First, an increase of 1°C correlates with three nights of insufficient sleep. In addition, seasons affect sleep – quelle surprise – and difficult sleep increases due to summer; the authors couldn’t establish such a strong relationship with sleep in the other seasons. Now, what about some of the other variables that I was talking about earlier? The authors found that the effect of temperature on lack of sleep is actually greater for those with incomes lower than $50,000 (make your own jokes about paying the electricity bill here, I’m just here for science and coffee) as well as those older than age 65. You would think that combining these two things really jacks up the temperature effect, and you’re right – according to the author, the temperature effect on insufficient sleep is ten times higher for older, lower-income individuals. Any sociologists reading sci.casual want to weigh in on this?
The authors did note that all they had to go on with regards to ‘insufficient sleep’ was each respondent’s perception of what is sufficient sleep. People have different needs for sleep, after all. There may be other factors involved that maybe other surveys can look at, like maybe even how much each respondent works in a week, what their jobs are, and so on. Sure, introducing more variables can make the linear models get wonky, but from what I know of sociology, human beings are rarely ever that simple.
Something to think about as you drift off to sleep. Good night.
Featured Article: Obradovich N, Migliorini R, Mednick SC, Fowler JH (2017). Nighttime temperature and human sleep loss in a changing climate. Science Advances 3(5), e1601555. DOI: 10.1126/sciadv.1601555
Featured Image: Public Domain (Author: Foundry Co, 2014)