Our moods are highly dependent on our sleep cycles. Fitbit data proves it.
The pace of life continues to accelerate, with many sacrificing a good night's sleep to cross out more things from their to-do lists. This comes with a price, as a lack of sleep is very much linked to our moods and overall happiness.
A research group at the University of Michigan has conducted a study that revealed this to be more than true.
Fitbit data used to determine the effects of disturbed sleep
The gadget that helped researchers reach such a conclusion was something that many of us wear daily – a Fitbit. They used data gathered from the Intern Health Study project, which works with hundreds of first-year training physicians. The interns wore fitness trackers that monitored their heart rate, activity, and sleeping habits.
The researchers developed algorithms to assess Fitbit data and extract quantitative information about people's circadian rhythms, sleep cycles, and how well they align. They aligned the results with mood surveys, which participants consistently completed.
The central circadian clock, located in the brain's suprachiasmatic nuclei, keeps time and coordinates other peripheral circadian clocks throughout the body. In their study, the team focused on the peripheral clock in the heart.
For most people, the heart's peripheral clock ensures it’s prepared to be more active at 2 p.m. than at 2 a.m. The team also measured the interns' sleep cycles, finding that when a sleep cycle was out of sync with the heart's peripheral clock, it negatively impacted mood.
"Specifically, the misalignment between the central circadian clock and sleep exhibited the strongest negative association with mood and depressive symptoms, including poor sleep, appetite issues, and even suicidal thoughts," said Dae Wook Kim, another lead author of the study.
When the central circadian rhythm was misaligned with the sleep cycle – particularly during shift work – it caused even more significant mood disturbances. In this case, the mismatch between the central clock and sleep cycle had a stronger negative effect on mood than the peripheral mismatch.
Getting enough sleep is crucial
The study results showed that if sleep cycles are not aligned with the internal clock or circadian rhythms, they can have drastic effects on emotional health and mood. Previous research on the subject linked the quality of sleep with serious mental health concerns, including suicide.
So basically – does that mean that getting a good sleep might solve many of our problems? The researchers remain cautious. "This is not going to solve depression. We need to be very, very clear about that," said Daniel Forger, lead author of the study.
"But this is a key factor that we can actually control. We can't control someone's life events. We can't control their relationships or their genetics. But what we can do is very carefully look at their individual sleep patterns and circadian rhythms to really see how that's affecting their mood."
The researcher adds that it is important to remember that happiness depends not only on going to sleep early but also on aligning with one's internal sleeping rhythms.
The research is published in the journal npj Digital Medicine.
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