This past round of four’o’clocks was particularly grueling for my roommate. Her 20 credits and endless motivation meant that adequate sleep was not an option. I watched her droop, visibly, after a scant four or five hours of sleep. As a burgeoning sleep researcher, it pains me to watch the people I love try to fight against the grueling cycle of shortened sleep leading to reduced productivity and even shorter sleeps.
Nearly everybody knows that they should be getting eight hours of sleep each night. According to Dr. Mary Carskadon, Ph.D., who ran the Bradley Sleep Lab where I researched this past summer, ideally we should be sleeping 8.4 hours every night. Yet, in a 2013 Gallup poll, 65 percent of Americans reported sleeping less than eight hours a night. While most people understand the importance of adequate sleep, as a society we don’t put that knowledge into practice.
Getting trained in sleep science, however, introduced me to the research that helps me take advantage of all that sleep has to offer. In this column I’ll share some of my favorite things I learned about sleep with the hope that they can help improve your sleep and quality of life- even if you cannot always make time for your 8.4 hours.
Most of my friends acknowledge that drinking caffeine late at night makes it harder to fall asleep. However, fewer recognize that caffeine has detrimental effects when consumed in the latter half of the day, even if they have no problem falling asleep. Researchers at the Michigan-based Henry Ford Hospital’s Sleep Disorders and Research Center found that sleep quality and quantity were both significantly reduced when caffeine was consumed three hours and six hours before bed. The group that had caffeine six hours before bed still suffered from the detrimental effects of reduced sleep the next day. Yet, they didn’t notice that they were sleeping worse. Thus, even if you don’t notice any lasting effects from your afternoon coffee, it still diminishes the benefits of sleep.
Going to bed with caffeine in your system also affects your sleep architecture, which is the organization of your sleep stages. In a normal night of sleep, you progress through 90-minute cycles that consist of light sleep, slow wave sleep and REM sleep. At the beginning of the night, slow wave sleep predominates and takes up much of each cycle. This restorative sleep is essential for repairing the body and mind to prepare for the day ahead. Towards the end of the night, REM sleep and dreaming predominate. However, with caffeine in your system before bed, REM sleep predominates at the beginning of the night and slow wave sleep predominates at the end.
Though both deep and REM sleep are vital for proper functioning while awake, deep sleep plays an especially important role in retaining declarative memories of facts and information. By drinking coffee to stay up late studying for a test the next morning, we are likely cutting short the slow-wave sleep that helps us retain the declarative memories we need to perform well on exams. Cramming for an exam is often inevitable, but by restricting caffeine use to the morning we can maximize the retention of everything we study.
Over the summer, I also learned about napping. Walking through the poster hall at the Sleep Research Society’s SLEEP 2015 conference, I encountered dozens of posters on both the benefits and detriments of napping. While naps can improve cognitive performance and energy levels in certain cases, they can also misalign one’s circadian rhythm.
One study I learned about at the conference found that regular nappers experienced cognitive benefits after taking a nap. However, when infrequent nappers took a nap, their cognitive performance was significantly worse for at least 20 minutes afterward. Even when these non-nappers were trained for four weeks to nap more frequently, their post-nap performance did not improve.
Another study found that furthermore, hour for hour, naps are not as good at reducing sleep pressure as nighttime sleeping. A potential reason for this might be that our circadian rhythm staves off sleep at certain times of the day. My personal rule is that if I must nap to get all 8.4 hours of sleep, I definitely will, but whenever possible I’ll reap the benefits of sleeping 8.4 hours straight through the night.
Getting good quality and adequate sleep has endless potential to improve your mental, emotional and physical health. Looking at sleep as an opportunity to improve your waking functions and productivity can eliminate the attitude that sleep is the first thing to cut when we don’t have enough time.
Rather, sleeping well through the night allows you to make the most out of your day so that you will always have time for your 8.4.