Date: June 1, 2023

Last Update: April 9, 2026

Author: Roberto Barata

How to cite: Barata, R. (2023). Dogs and Sleep: The Forgotten and Underestimated Need. Human-Animal Science.

 

What is the circadian rhythm in dogs?

The circadian rhythm in dogs follows a roughly 24-hour periodicity that governs hormone levels, body temperature, and behavioral transitions between sleep and wakefulness. In adult female beagle dogs, serum cortisol concentrations rise with the onset of light, reaching their peak between 10:00 a.m. and 12:00 p.m., and then gradually decline through the dark phase of the cycle (Palazzolo & Quadri, 1987). Puppies, by contrast, lack a fully developed circadian cortisol rhythm, which only matures as they grow. Salivary cortisol, a measure of the hormone’s free fraction, mirrors the pattern observed in serum and peaks at the end of the light phase under natural day-night conditions (Giannetto et al., 2014).

Body core temperature in dogs oscillates in parallel with these hormonal rhythms. It tends to be highest during the afternoon, peaking roughly one hour before lights-off. The molecular underpinnings of this system involve clock genes, particularly per1, which is induced by glucocorticoids and has been identified in canine peripheral blood mononuclear cells. Because per1 expression follows a circadian pattern, it may serve as a molecular marker for monitoring circadian function and for studying how pharmacological agents affect the canine biological clock (Ohmori et al., 2013).

 

How does the circadian rhythm in dogs affect their behavior?

Dogs are polyphasic sleepers, meaning they distribute their sleep across multiple bouts throughout the day, with the largest concentration during the night. They follow a broadly diurnal pattern, with most of their activity occurring during daylight hours. Schork et al. (2022) documented how sleep structure is influenced by sex, age, activity level, and environmental conditions. Pre-sleep activity improved sleep quality in the dogs they studied, while disrupted sleep patterns reduced motivation and daytime activity. Dogs that slept longer exhibited fewer active behaviors overall and spent more of their waking time eating, a pattern the authors interpreted as a possible sign of reduced behavioral richness.

Sleep duration itself may function as a welfare indicator. In shelter populations, sleep that is longer or shorter than typical for a given age and context has been associated with behavioral changes suggesting compromised well-being (Owczarczak-Garstecka & Burman, 2016). These findings reinforce the idea that sleep is not a passive state to be overlooked, but an active physiological process with direct consequences for how a dog moves through its day.

 

Sleep, Memory, and Learning

Sleep is fundamental for cognitive homeostasis, and its role in memory consolidation and learning has been the subject of growing investigation in dogs. Kis et al. (2017) provided the first evidence of sleep-dependent memory consolidation in this species, using a fully non-invasive polysomnography protocol. After a command-learning task in which dogs associated unfamiliar English words with already known actions, polysomnography recordings revealed changes in EEG spectral power during both REM and non-REM sleep. Delta activity increased during non-REM sleep, and theta activity increased during REM sleep, patterns that broadly parallel those reported in human studies. Performance on the learned commands improved after three hours of sleep, and this improvement correlated with specific EEG spectral features, suggesting that the newly acquired information was being reprocessed during sleep.

Iotchev et al. (2017, 2020) extended these findings by analyzing sleep spindles, the brief oscillatory bursts that appear during non-REM sleep and are widely considered markers of memory consolidation across mammalian species. Spindle density was higher in the learning condition compared to the control, and it correlated with the degree of learning gain during sleep. Averaging spindle occurrence across measurements proved to be a better predictor of cognitive performance than any single recording, suggesting that trait-level spindle density reflects a stable individual capacity for sleep-dependent consolidation (Iotchev et al., 2020).

In a 2024 study published in Scientific Reports, Carreiro et al. found that the emotional context of a training session interacts with subsequent sleep processing. Dogs that experienced a positive expectancy violation, receiving a more permissive and rewarding training style than they had come to expect, showed improved post-sleep learning performance. Earlier work from the same group had demonstrated that negative emotional pretreatment, such as owner separation or the approach of a threatening stranger, altered sleep macrostructure by decreasing drowsiness and increasing REM sleep (Kis et al., 2017b).

Most recently, Bolló et al. (2025) adapted a targeted memory reactivation paradigm for dogs, re-exposing them to one of the previously learned command signals during sleep. This study, published in eNeuro, represents an effort to move from correlational findings toward experimental manipulation of memory consolidation during canine sleep, a direction that could eventually inform how trainers and behavior consultants schedule rest periods around learning sessions.

 

Sleep Deprivation and Its Behavioral Consequences

The consequences of insufficient sleep in dogs parallel much of what is known from research in humans and rodents. Schork et al. (2022) reported that sleep loss in kennelled laboratory dogs affected activity patterns, increased anxiety-like behaviors, decreased cognitive performance, and was associated with states resembling depression. Their data showed that dogs prevented from sleeping during the day compensated with longer, more continuous bouts at night, a rebound effect consistent with findings across species. Female dogs in the study recovered more efficiently from sleep deprivation than males, displaying longer slow-wave sleep bouts, a result that aligns with sex differences in sleep recovery observed in humans and rats.

Carreiro et al. (2023) investigated the relationship between owner-rated hyperactivity and impulsivity and sleep efficiency measured by non-invasive EEG. Dogs described by their owners as more hyperactive and impulsive showed less total sleep time, a reduced percentage of REM sleep, and lower spindle density. This finding is worth careful consideration by trainers and behavior consultants, because it suggests that what presents as a behavioral problem, the hyperactive, impulsive, hard-to-settle dog, may in some cases reflect or be compounded by poor sleep quality rather than a simple need for more physical exercise.

Chronic cortisol dysregulation compounds the problem. Cortisol normally follows a diurnal rhythm, rising in the morning and tapering through the evening. In dogs experiencing prolonged sleep disruption, cortisol levels can remain elevated at inappropriate times, sustaining a state of physiological readiness that further fragments sleep and drives heightened reactivity (Beerda et al., 1999; reviewed in Fernández-Lázaro et al., 2024). The result can become cyclical: poor sleep elevates stress, which in turn degrades the conditions for restorative sleep.

 

Sleep and Aging

Mondino et al. (2023) used polysomnography to compare sleep in aging dogs with varying levels of cognitive decline and demonstrated that dogs with higher dementia scores spent less time in both NREM and REM sleep. Delta power during drowsiness declined with age, consistent with findings in humans, rats, cats, and other dogs that show reduced slow-wave activity as a hallmark of aging sleep. The study also identified correlations between REM sleep power and memory scores, reinforcing the idea that REM sleep is where much of the consolidation work occurs.

These findings support a bidirectional model: neurodegenerative processes, including amyloid-beta accumulation, can disrupt sleep, and disrupted sleep, in turn, impairs amyloid clearance via the glymphatic system, which is primarily active during slow-wave sleep. This cycle has been well documented in human Alzheimer’s research and appears to hold in canine cognitive dysfunction syndrome as well. For practitioners working with senior dogs, these data suggest treating sleep quality as a priority rather than an afterthought in managing age-related cognitive decline.

 

Developmental Sleep Patterns

Population-level data from the Generation Pup longitudinal study (Sheridan et al., 2020) documented sleep patterns in over 2,000 puppies at 16 weeks and again at 12 months of age. Owners reported that younger puppies slept longer during the day and throughout the full 24-hour period, but less during the night, compared to 12-month-old dogs. At both ages, dogs were most commonly settled by being left in a room without human company.

These population norms are useful for practitioners and owners alike. A puppy that sleeps through much of the day is not necessarily ill or understimulated, it is following a typical developmental trajectory. Conversely, a young dog whose sleep patterns deviate markedly from these norms may warrant closer attention. The study also highlighted that owner-reported sleep data, while imperfect, remains the most practical method for gauging sleep duration in clinical and applied settings, given that polysomnography requires specialized equipment and is best suited to controlled research environments.

 

A Powerful Therapy Ally

Sleep is vital for maintaining dogs’ physical and cognitive health. It supports immune system regulation, metabolic stability, cognitive well-being, and joint health. Bódizs et al. (2020) and Mondino et al. (2023) have both emphasized that sleep is when memory consolidation and learning processing occur, making dogs a valuable non-invasive translational model for broader sleep research.

Some trainers and owners prioritize draining a dog’s energy through physical exercises like tug-of-war and chasing games. It is worth remembering that domestication did not produce an organism designed to match human work schedules inside an apartment. Every living organism’s biological default is to conserve energy, and the assumption that more exercise always produces a calmer, better-adjusted dog deserves scrutiny. In my experience, employing human-imposed routines to schedule exercise, manipulating instinctual drives through repetitive high-arousal games, and ending sessions based on the dog’s apparent satiation rather than its actual physiological needs can do more harm than good. Problems of under- or overstimulation are rarely resolved through physical exercise alone, and poorly timed or excessive activity can degrade both daytime behavior and nighttime sleep quality.

My own empirical work in behavior modification programs has consistently shown that improvements in lifestyle, specifically the integration of olfactory stimulation, longer walks at the dog’s own pace, and a commitment to structured rest and appropriate sleep practices, produce better outcomes than programs relying heavily on physical exercise, overstimulation through ball-throwing and tug games, and insufficient attention to sleep routines (for example, leaving lights on at night, failing to provide opportunities for solitary sleep, and similar oversights).

 

Best Practices

Sleeping Alone

Allowing a dog to sleep alone offers measurable benefits that justify serious consideration. Adams and Johnson (1993) showed that external disturbances, movements, and sounds caused by other household members reduce the likelihood of uninterrupted sleep. A more recent polysomnography study by Carreiro et al. (2025) found that family dogs sleeping in the absence of their owners exhibited altered sleep macrostructure consistent with reduced sleep quality, lending experimental weight to the practical observation that the presence of others can fragment canine rest. Solitary sleep also serves as a supplement in addressing what owners commonly report as home-alone problems (Abrantes, 2015), by teaching the dog that being alone is a safe, ordinary state rather than a source of distress.

Electromagnetic Radiation

Electromagnetic radiation (EMR) exposure can affect sleep patterns in both humans and dogs, producing a range of endocrine, health, and behavioral changes (Earth and Life Studies et al., 1993; Reif et al., 1995). Hart et al. (2013) observed that dogs align their defecation behavior with the Earth’s magnetic fields, leading the researchers to conclude that continuous exposure to artificial electromagnetic fields may influence this and other behaviors. Reducing exposure to EMFs by keeping dogs away from major electrical sources, turning off routers and radio-frequency devices at night, and conducting an EMF assessment of the home environment can contribute to better sleep for both dogs and their human companions.

Darkness and Melatonin

Melatonin, the hormone synthesized by the pineal gland in response to darkness, exerts a substantial influence on mammalian sleep. Often called the “hormone of darkness,” melatonin is produced during periods of low light in both diurnal and nocturnal species, and its nocturnal secretion plays a central role in regulating sleep patterns (Masters et al., 2014). Light exposure, particularly short-wavelength blue light, has been shown to suppress melatonin secretion by acting through melanopsin in retinal ganglion cells, which relay signals to the suprachiasmatic nucleus (Yoon et al., 2025). Even relatively dim artificial light during the natural dark phase can interfere with melatonin production, leaving the dog’s circadian system confused and receiving conflicting temporal signals.

The practical implication is straightforward: a completely dark sleeping environment supports optimal melatonin production and, by extension, better sleep architecture. Dogs who sleep in rooms with persistent artificial light, screens, or standby LEDs may never achieve the deep, restorative phases their physiology requires, even if they appear to be resting for adequate periods.

 

New Directions: Technology, Methodology, and Welfare Assessment

The methodological landscape of canine sleep research has changed considerably since Kis et al. developed non-invasive polysomnography for dogs in 2014. The protocol has since been validated for reliability (Gergely et al., 2020), applied to wolves (Reicher et al., 2022), and used in a growing number of studies examining the relationships between sleep, emotion, learning, and welfare.

On the technological side, Schork et al. (2024) developed a convolutional neural network system capable of detecting and quantifying sleep duration and fragmentation in dogs, achieving 89% agreement with human behavioral observation. The automated system captured more total sleep time than the human observer, likely because continuous monitoring captures brief sleep episodes that manual observation might miss. Tools like these may eventually allow veterinary clinics and shelters to incorporate sleep assessment into standard welfare evaluations, something that the time-intensive nature of manual observation has historically prevented.

The broader welfare literature has also begun to incorporate sleep more explicitly. A 2024 review of cortisol’s physiological and behavioral roles in dogs (Mârza et al., 2024) emphasized the interconnection between environmental stressors, cortisol regulation, and behavioral outcomes, with sleep functioning as both an output of stress and a moderator of the stress response. As large-scale longitudinal projects like Generation Pup, the Dog Aging Project, ManyDogs, and VetCompass continue to accumulate data, the field is moving toward a more integrated understanding of how sleep fits into the broader picture of canine welfare across the lifespan.

 

Conclusion

The significance of sleep for canine health, learning, emotional regulation, and overall welfare is now supported by a substantial and growing body of evidence. Based on my empirical research and professional experience, I recommend that all behavior consultants review the criteria used in their dog behavior evaluations and ask whether sleep and rest states are being assessed with the seriousness they deserve. It is no longer sufficient to treat sleep as a background variable. Consultants and trainers should develop a working knowledge of mammalian sleep physiology, stay current with the expanding academic literature, and develop tailored strategies for counseling dog owners on sleep hygiene, light management, rest schedules, and integrating sleep-supportive practices into behavior modification programs.

The evidence reviewed here, from polysomnographic studies of memory consolidation to population-level data on developmental sleep norms, from the metabolic consequences of sleep deprivation to the role of melatonin in circadian regulation, converges on a single conclusion: sleep is not a luxury for dogs, and it is not an afterthought in behavioral assessment. It is a biological need that, when properly supported, improves learning results, reduces stress-related behaviors, and contributes to a healthier, more livable life for the dog and the people around it.

 

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