Circadian Rhythms
In 2017, the Nobel Prize for Physiology or Medicine was awarded to researchers Jeffrey C. Hall, Michael Rosbash and Michael W. Young who studied the mechanisms that govern our biological clock. They studied fruit flies and were able to shed light on the crucial processes that modulate our 24-hour sleep-wake cycle. They were worthy winners, as they were able to isolate the gene that controls the circadian rhythms which support our 24-hour day. Our internal clock shifts and balances our physiology as we move through our daily lives. An essential component of our circadian rhythm is sleep. Data from Statista suggests that only 10% of Americans prioritize sleep over fitness/nutrition, work or hobbies.
Sacrificing Sleep
Olivia Walch and colleagues from the University of Michigan examined sleep schedules derived from mobile phone apps of 10,000 people from 20 countries. They report in Science that an essential factor for sleep was bedtime as opposed to wake time. Women get more sleep than men. On average, Americans went to bed just before or at 11 pm and woke before 7 am. Our sleep patterns and bedtimes also change as we age, which usually results in poorer sleep quality.
While some data suggested Americans were sacrificing sleep for other activities, a new study by Mathias Basner and David Dinges from the University of Pennsylvania published in Sleep last month indicates that public health efforts to promote the importance of sleep may be paying off. They looked at sleep duration between 2003 and 2016 in over 181,000 participants and found that over the term of the survey, weekday and weekend sleep quantity showed an increased trend in both students and working adults; this trend did not hold for those who were unemployed or not in the labor force. They also saw changes in evening activities such as TV watching or reading; those who went to bed earlier engaged less in these pre-bedtime activities. They suggest that due to the increasing ability to watch TV or run errands online at any time, more free time in the evenings could be devoted to sleep or going to bed earlier.
Sleep as Gardener for the Brain
Why is rest so important? One theory suggests that as we move through the sleep cycles during the night, the brain can engage in some “synaptic pruning’, as featured in Scientific American earlier this year. Christopher Wanjeck’s article profiles the research by Dr. Cirelli and colleague Dr. Giulio Tononi of the University of Wisconsin-Madison, who proposed the concept of Synaptic Homeostasis, i.e., sleep allowing our brain to focus on pruning the communication channels for which synapses play a crucial role in ensuring that communication occurs smoothly. Their more recent research in mice showed the synapses shrinking during sleep. They liken our daily wake time habits to a busy highway, with lots of traffic and lots of things for our brains to pay attention to from moment to moment. During sleep, the road has less traffic, thus enabling the brain to prune the unnecessary information so that on waking, we are refreshed and ready to learn new things.
Sleep and Mood – What’s the Connection?
Finally, in the latest issue of Lancet Psychiatry, Lyali and colleagues from the University of Glasgow (and associated institutions) examined the association between sleep disturbance, mood, well-being, and cognitive function in over 91,000 participants in the UK Biobank cohort, using data derived from wearables. They collected data from 2013 to 2015, during which participants wore a wrist-based accelerometer. The authors were able to calculate a 24-hour rest-active cycle to develop a circadian rhythm for the cohort. Using statistical modeling, they were able to look for trends in the sample; findings reliably showed that disruptions in the wake-sleep cycle were associated with a significant adverse impact on mood, well-being, and cognitive function. Sleep disruption was associated with an increased lifetime risk for major depressive disorder and bipolar disorder. More substantial disruptions also decreased happiness and health satisfaction, increased loneliness, and impaired reaction times which could have significant implications for quality of life and workplace safety.
All these findings point to the importance of sleep. As children, naptime was a regular part of our day; we now know infants and children sleep so much because it supports brain development. It would seem that sleep is essential for brain and overall health as we age, too. Some companies are even starting to feature nap pods as an office perk; they may be onto something! Prioritizing sleep would appear to be an essential building block for health and well-being, and it should hold a place in prevention strategies going forward.
Thanks for reading- Trina
(Opinions are my own)
References
2017 Nobel Prize in Physiology and Medicine
https://www.nobelprize.org/nobel_prizes/medicine/laureates/2017/press.html
Percentage of adults in the U.S. that prioritized select aspects of their lives over sleep as of 2018
https://www.statista.com/statistics/827053/health-and-social-priorities-over-sleep-us/
Sleep Habits by Country
http://advances.sciencemag.org/content/2/5/e1501705/tab-pdf
Sleep duration in the United States 2003–2016: first signs of success in the fight against sleep deficiency?
https://academic.oup.com/sleep/article-abstract/41/4/zsy012/4792945?redirectedFrom=fulltext
Synaptic Pruning
https://www.scientificamerican.com/article/sleep-shrinks-the-brain-and-thats-a-good-thing/
Disruptions in Circadian Rhythms and associations with mood, well-being, and cognitive function.
https://www.thelancet.com/journals/lanpsy/article/PIIS2215-0366(18)30139-1/fulltext
