Newsflash! Sleepless nights and irregular sleep-wake schedules are doing you no favors! 

Getting enough quality sleep that is in sync with your circadian rhythm is crucial for optimizing and maintaining daytime performance.¹ Notice, we didn’t say “good sleep.”  This is because we probably should avoid applying “good”,“bad” or “poor” as descriptions for our sleep, as they can create stigma limiting us from acknowledging and discussing our sleep-wake and circadian habits.  When looking at sleep health, there is not a singular agreed upon definition and frequently is represented by the absence of sleep problems, such as trouble falling asleep or staying asleep, or, on a positive note, feeling mentally and emotionally well. Overall, if we were to boil down the key ingredients of circadian and sleep health it would be with a focus on the duration, timing, and regularity of sleep, as well as the quality of our sleep and our wakefulness and performance. Understanding the role and value of your sleep health, and circadian rhythm gives you the opportunity to use them as a tool for your overall health, wellness, and performance.  

Maximize Memory and Cognitive Performance

Research has shown that, for adults, sleeping at least 7 hours per night is associated with the highest cognitive performance. Numerous researchers have studied this topic and found similar findings. Let’s take a look at one recent study.

When Tai and colleagues² studied sleep in middle-aged and older adults, they found that those people who got about 7 hours of sleep each night had better thinking and memory skills, as compared with people who slept more or less than 7 hours. How did the researchers discover this? They examined MRI scans of the study participants and found that those who slept between 6 and 8 hours had more gray matter—a key part of the brain that helps with decision-making, memory, and movement. (More gray matter is better.) Some brain areas were smaller in the adults who slept too much or too little, whereas others were smaller only in people who slept a lot. These finding shows that sleep duration can affect both thinking and brain health.²

Improve Athletic Endurance, Strength, Reaction Time, and Accuracy, Healthy sleep, including sufficient quality and quantity obtained at the right time, improves athletic endurance, strength, reaction time, and accuracy. Conversely, sleep loss negatively impacts exercise tasks, particularly in the evening.³ Some of the early research on this topic was conducted by Dement and his colleagues at Stanford University.

Reduce Errors, Risk-Taking Behavior, and Poor Judgment

Healthy sleep and circadian rhythms help to restore cognitive functions, that is, help people to think more clearly. Sleep loss is particularly detrimental to the part of the brain known as the prefrontal cortex. This brain region is essential for decision-making, attention, and impulse control. Adequate sleep improves logical thinking, working memory, and attention. Working memory involves the ability to hold and process information. A strong working memory reduces simple mistakes and helps people pay attention to details.

Sleep deprivation affects the dopamine pathways, a part of the brain involved in the reward system. When people are sleep deprived, they are more likely to seek immediate gratification, to take risks, and to underestimate the negative consequences of their behavior. Studies show that tired individuals are more likely to gamble, speed, or make impulsive financial and social decisions. The Centers for Disease Control and Prevention⁵ says that being awake for 17 hours causes the same impairments as a blood alcohol concentration (BAC) of 0.05; a 24-hour awake period equals a BAC of 1.0. Unfortunately, people who are sleep deprived often do not recognize their own sleepiness and, therefore, may not be aware of the impact of their sleepiness on their decision-making capabilities.

The part of the brain called the amygdala processes emotions such as fear and anger. When people are sleep-deprived, their amygdalas become overactive, and, as mentioned previously, the control of the amygdala by the prefrontal cortex is weakened, leading people to become too emotionally reactive, have poor judgment, and make irrational decisions. Healthy sleep results in people being able to make calm, rational decisions. 

Sleep, especially rapid eye movement and deep sleep, is necessary for the brain to consolidate learning and experiences, reinforcing correct patterns and helping the brain to identify and correct mistakes. This is why an all-nighter is not the way to prepare for a big exam; deep sleep is needed to be able to store the studied information and retrieve it when taking the test. Sleep improves not only memory, but also the ability to learn from past errors or mistakes.

This section has discussed primarily the effect of sleep duration on errors, judgment, and risk taking, but sleep quality also has an impact on cognition and errors. Hassinger et al⁶ captured actigraphy data from 3654 doctors in their first year of training after medical school. They found that sleep efficiency, but not sleep duration, was associated with the likelihood of committing a medical error.

Wake Refreshed and Ready to Crush Your Day 

Researchers have found that sleep quality is based upon two factors: 1) having a subjective sense of having experienced refreshing sleep, and 2) sleep continuity, which is falling asleep and staying asleep over an optimal length of time.⁷ Therefore, to experience that feeling of waking up ready to hit the ground running, sleep hygiene should be optimized, and 7-9 hours should be set aside to sleep without interruptions. 

Give Yourself More Productive Hours by Improving Attention, Time Management, and Execution of Tasks

Have you heard the saying “Work smarter, not harder”? This applies to your sleep and circadian health. When you prioritize the timing, duration and quality of your sleep, you are able to be more focused and productive during the day. 

Healthy sleep has a positive impact on productivity. When comparing worker productivity with regard to sleep duration, researchers have found that workers who report sleeping 7-9 hours per night have a 1.5 percentage point higher productivity rate than those who sleep 6-7 hours.⁸ Extrapolating that data to the typical number of working days per year (ie, 250) finds that, as compared with workers who sleep 7-9 hours, those who sleep 6-7 and less than 6 hours lose 3.7 and 6 work days, respectively, per year due to absenteeism or presenteeism. 

Insufficient sleep is detrimental to the health of all people; however, school-aged children and adolescents are particularly vulnerable to the effects of restricted or inadequate sleep. Children who are sleep deprived don’t look groggy or sluggish like adults with sleep deprivation; instead, in children, sleep deprivation often manifests as hyperactivity. Attention-deficit/hyperactivity disorder can be caused by sleep disorders, and it can also result in a sleep disorder. Long-term consequences include poor school performance and decreased cognitive ability. This is a significant problem, as almost 90% of high school students in the United States do not get the recommended amount of sleep for their age group. 

Insufficient sleep impairs brain functioning and results in well-documented cognitive deficits in attention and alertness.⁹ One of the important cognitive functions that is associated with sleep or sleep deprivation or restriction is response inhibition, meaning the ability to stop a preplanned or ongoing action. Response inhibition is important for managing responses in high-stress situations, but is worsened by sleep loss. As a sleep researcher said many years ago at a conference, “Deprivation brings perseveration. When we are sleep deprived, we keep repeating the same behavior, anticipating a different response.”

Enhance Your Mental Health and Wellness

Because sleep plays a critical role in regulating emotions, stress response, and the stress system,¹⁰ healthy sleep and circadian rhythms are crucial for mental health.¹¹ Researchers have found that there is a 2-way or bidirectional relationship between sleep, with psychiatric symptoms causing disturbed sleep, and disturbed sleep (primarily insomnia) being a risk factor for the development of new-onset psychiatric disorders and for relapse and recurrence.¹²

Almost all mental health disorders include a component of sleep disturbance.¹⁰ As Meyer says,¹¹ “Sleep-circadian disruptions are the rule, rather than the exception, across every diagnostic category of psychiatric disorder. In addition to being a risk factor for the subsequent development of psychopathology, problems with sleep and its timing are one of the earliest signs of relapse. Challenges to the sleep–circadian system through night shift work increase the risk of developing depression and anxiety disorder, while 8% of individuals with depression experience deterioration in mood over winter, implicating shortened day-length and changes in light exposure in mood disorders.” Fortunately, new research has shown that targeting treatment to improve sleep and circadian rhythm disturbances can improve psychiatric symptoms in people who have both sleep and mental health disorders. Numerous studies have shown that sleeping less than 8 hours a night can lead to anxiety and depression, mental health issues that have far-ranging effects. The presence of insomnia may predict suicide attempts.¹⁰ 

Nurture Relationships and Even Intimacy

Engaging in intimacy, including sexual activity, can have a positive impact on sleep. Sleeping in the same bed with a partner can lead to a deeper physical and emotional connection, resulting in reduced stress, improved relaxation, and better sleep quality. Sexual activity can lead to the release of hormones such as oxytocin and prolactin, which have sleep-promoting effects.

On the other hand, poor sleep, such as insomnia and sleep deprivation, can cause sexual dysfunction.¹³ When people are sleep deprived, instead of producing sex hormones like estrogen and testosterone, their brains may release more cortisol, which may result in lower interest in sex, infertility, and erectile dysfunction. Finally, sleep deprivation may simply make people too tired to be interested in intimacy. So, the bottom line is that good-quality sleep can help to optimize relationships.

Prevent Illness and Improve Chronic Disease Management

In 2022, the American Heart Association (AHA) added sleep to its cardioprotective preventative strategies, changing Life’s Simple 7 to Life’s Essential 8, highlighting the role of healthy sleep in the prevention of cardiovascular disease.¹⁴ In 2025, the AHA took this a step further and outlined the concept of “multidimensional sleep health” as it concerns health related to the heart and blood vessels and how the body uses food for energy–cardiometabolic health (CMH).¹⁵ As we discussed in How Do I Keep my Sleep Healthy, optimizing the quantity, timing, quality, and all dimensions of sleep is important to achieving not only the best overall health, but, according to the AHA, the best possible CMH. Research has shown that sleeping between 7 and 9 hours (7.5 hours is optimal), falling asleep between 10 and 11 pm, sleeping uninterrupted, and being satisfied with sleep are all associated with a lower risk of various cardiovascular and metabolic conditions.¹⁵

Throughout the world, millions of people don’t get enough sleep to maintain metabolic health (that is, the process of converting food and drink into energy to power their cells is not working properly). Millions of other people work or participate in social activities that are out of alignment with their circadian rhythm, that is, they are awake when their body is promoting sleep. Inadequate sleep and circadian misalignment often lead to increased calorie intake in response to reduced sleep, eating food out of sync with the body’s internal clock (when the body is not prepared to process the food), reduced energy expenditure while awake, and disrupted glucose metabolism. All of these, in turn, predispose the individual to having poor metabolic health. Researchers have found that, in addition to the long-established risk factors for poor metabolic health, such as a poor diet and inadequate exercise, disturbed sleep and circadian rhythms are also risk factors that can be modified to prevent and treat metabolic diseases and promote a healthy metabolism.¹⁹

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