Researchers have long known that a poor night of sleep can lead to long-term consequences; multiple studies have linked disruptions in our sleep cycles with an increased risk of tumor formation or a worsening of existing disease.1 In a society that has long undervalued the importance of sleep, researchers are now increasingly focusing on how individuals can improve their ability to recharge. Fiona Barwick, PhD, a clinical assistant professor of psychiatry and behavioral sciences and director of the Sleep and Circadian Health Program within the Stanford Heath Care Sleep Medicine Center in Stanford, California, says that our slumber depends on 3 main systems. Sleep drive is a biological drive that works much like hunger; it builds as we awaken and becomes active, and then it declines as we sleep. The second is a circadian system that regulates much of our behavior and physiology and is in turn regulated in large part by changes in the light-dark cycle. The third system is stress, which can disrupt sleep through a state of hyperarousal. Multiple studies suggest that circadian disruption is a probable cancer risk, especially among shift workers. Greater light exposure may inhibit the production of melatonin, which not only promotes sleep but also enhances the immune system and suppresses tumor formation. The links between cancer and sleep loss are less clear, Dr. Barwick says, although a reduction in sleep opportunities due to work, chronic pain, or other life events has been associated with adverse health consequences such as heart attacks, stroke, diabetes, and high blood pressure. Cancer-related pain and fatigue may reduce activity levels and thus lower sleep drive, whereas cancer can dramatically increase stress levels. “Stress disrupts sleep for all of us. When you combine it with a lower sleep drive, it's going to be even more likely to keep you awake at night,” Dr. Barwick says. Some patients with cancer have higher rates of insomnia, which interferes with sleep ability rather than opportunity. “With the sleep loss, if you were in bed, you'd actually be asleep,” she says. “With insomnia, you're in bed and you're awake.” The underlying mechanisms are unclear but may be due to an increased level of arousal at night. “It's ironic to me because people seem to put more faith in medications or procedures that have been developed over the past, say, 60 to 70 years. And they'll ignore the fact that their sleep-wake system has evolved over millennia to be particularly responsive to things.” –Fiona Barwick, PhD What has not changed over the millennia is our need to be physically active and to be exposed to daylight during the day and to darkness at night. Martin Lowery, an executive coach and organization development consultant in Palm Springs, California, says that it is particularly important to put away cell phones and other screens in the 1 or 2 hours before bedtime when natural light dims and melatonin levels rise. Blue light, which is emitted by computer screens, can suppress melatonin production. “Even if you're wearing blue light-blocking glasses, the content is the same,” Dr. Barwick points out. “It's quite clear: The content is going to be equally disruptive.” In his talks to physicians and business leaders, Lowery emphasizes sleep habituation and “sleep rituals” as ways to establish routines and free up essential bandwidth for the brain's overnight problem- solving functions. The more that the brain's suprachiasmatic nucleus—the body clock and putative regulator of circadian rhythms—can be programmed or conditioned for sleep with routines or rituals, he says, the better someone will sleep. Although those rituals should involve all 5 senses, Lowery says, most people do not consider more than 1 or 2. Light considerations, such as candlelight, dimmed light, a night light, blackout shades, and eye masks, can be critical. So can sound, whether silence, white noise, ambient sounds, or music that aids relaxation. Touch can include the feel and temperature of moving air, the pressure of a weighted blanket, or the firmness of a mattress. A range of calming herbal teas or warm milk can promote sleep, as can certain odors such as lavender. “It's not about one of the things; it's about the synergy of many of those things,” Lowery says. “Conditioning is so prevalent to human beings. Once you've got a really great ritual, it triggers this sense that, ‘Yes, now it is time for me to sleep and I'm going to sleep well.’” Although few research efforts have explored sensory input and sleep, a randomized controlled trial suggested that aromatherapy using lavender and peppermint oils significantly improved the sleep of patients with cancer according to a standardized measure called the Pittsburgh Sleep Quality Inventory.2 One of Dr. Barwick's colleagues also told her about the growing evidence for lavender use in sleep improvement. “I was surprised; that isn't something I would have predicted,” she says. The evidence, however, bolsters the idea that sleep depends on the alignment of multiple senses. Another key to improving sleep, Dr. Barwick and Lowery agree, is correcting the misconception that it should be a uniform or contiguous event. Humans sleep in cycles of roughly 90 minutes, although the cycles can vary between 80 and 110 minutes. In a typical night, a person might sleep for 5 or 6 cycles, or 7.5 to 9 hours in all (physicians recommend a minimum of 7 hours). Adults often awaken naturally after the second or third cycle; in medieval times, Lowery says, it was known as “the watch,” when people would get up; stoke the fi re, check the cattle, or read; and then go back to bed. “Now when people wake up in the middle of the night, they tend to freak out and think, ‘I've got sleep problems,’” he says. Dr. Barwick says that people often do not understand that sleep naturally changes with age. Unlike children, for example, adults normally wake up 10 to 12 times a night. The accepted definition of normal sleep is needing 30 minutes or less to fall asleep and spending 30 minutes or less being awake after that. “So, you can be awake for an hour at night and still have normal sleep for an adult,” she says. If people have not adequately wound down and reduced their stress before bedtime, however, Dr. Barwick says that sleeplessness often reemerges with a vengeance. “Your sleepy brain is more like a 2-year-old. It doesn't regulate emotions well, so it's going to go right for all the worst possible things,” she says. Normal sleep windows can also vary widely; adolescents tend to go to bed later, whereas older adults tend to go to bed earlier. However, Dr. Barwick has worked with some 80-year-olds whose normal bedtime is 1 am, whereas others are in bed by 8 pm. Both are normal rhythms as long as the schedules are consistent and both individuals get enough sleep. Similarly, Lowery says that some high-performing athletes get the right amount of sleep but space it out in increments of 90 minutes. The key, he says, is establishing a regular pattern. For those who have sleep disruptions, the usefulness of sleep trackers depends on the type of disorder being addressed. For people who lose sleep because they are minimizing their opportunities and not paying enough attention, Dr. Barwick says, a tracker can be useful. “They need to protect their sleep window more,” she says. However, sleep tracking can be harmful for people with insomnia, most of whom are already closely monitoring their sleep performance. The constant tracking, she says, can make them even more anxious about sleeping when their ability to do so depends on letting go of anxiety. For most people, Dr. Barwick says, getting a good night of sleep boils down to 3 main requirements. “Everyone needs to wind down and relax before bedtime. This is especially true if you have cancer because your stress level will be higher,” she says. Remaining active during the day will help people to build their sleep drive, and getting exposure to daylight will help to ensure that their circadian rhythms stay on track. Perhaps one of the biggest keys to better sleep is to avoid waiting too long to address any problems. “Sleep is like breathing: We sort of take it for granted,” Dr. Barwick says. “We don't realize it's something that we can impact, that our behaviors can change, that disorders can be identified.”