Awake at Night: Understanding Equine Sleep Disorders

For most horse owners, sleep seems simple. Horses lie down, rest and rise again. But when a horse refuses to lie down, shows unusual fatigue, or collapses unexpectedly, it signals a problem that can be both puzzling, destructive and perplexing. Understanding these behaviors and the medical issues that face these horses and their owners has been the focus of Dr. Joseph J. Bertone, a renowned equine veterinarian whose research into equine sleep disorders is helping to transform horse care and veterinary medicine.

Dr. Bertone, DVM, MS, Dipl. ACVS, is an emeritus professor of equine medicine at Western University of Health Sciences College of Veterinary Medicine and an adjunct professor at California Polytechnic Institute, Pomona. He earned his DVM and BS in nutrition from Cornell University and completed a residency and MS at Colorado State University. He also completed an FDA Fellowship in pharmacology. Over his career, he has taught at Louisiana State University and The Ohio State University, and worked with the FDA Center for Veterinary Medicine. An internationally recognized speaker, he has received numerous awards, including the Zoetis Teaching Award, and is known for integrating research, clinical practice and innovative teaching.

One of his interests has been equine sleep disorders. This began with an unusual case during his residency program. A horse was brought in for collapsing episodes, unwillingness to lie down and unexplained poor weight gain. A student walking alongside noticed a noise that sounded like rocks clinking together. Radiographs revealed two enteroliths, mineral stones, in the horse’s gastrointestinal tract. Surgery was employed to remove the stones, and within a few days, the horse began lying down – a behavior it had avoided for months. The horse no longer collapsed, and over the next few months gained weight to the level the owners expected.

“That first case really stuck with me,” Dr. Bertone recalled. “It wasn’t just the stones. It was the behavioral change; the horse avoiding lying down because of pain. I kept those stones in my office as a reminder of that moment. They were also pretty stones and now sit in my living room.”

His curiosity deepened after attending the BEVA Congress in England, where leading equine neurologist Dr. Joe Mayhew talked a few minutes about “sleep attack syndrome.” Over time, Dr. Bertone encountered more cases, building a career focused on understanding the causes and consequences of disrupted sleep in horses. With his website, he indicates he has dealt with over 1,800 cases and counting.

Consequences of Sleep Deprivation

Horses evolved as migratory prey animals and that formed their sleep physiology and behavior. This occurred in all mammalian species. All animals are paralyzed during REM/Paradoxical sleep (PS). That’s not a good thing if you are someone else’s dinner. As an aside, whales, dolphins, and other cetacean species don’t sink during REM/PS paralysis because they REM/PS with half their brain at a time. And to add, horses cannot achieve their entire sleep unless they lie down. Equine evolution provided for a short, 15-minute average need for REM/PS. They can go weeks without it, to support migration. Humans rely on longer, consolidated rest and long REM/PS periods, and they need it daily. While horses can rest while standing, true REM/PS can only occur when lying down. Disruptions in sleep can have profound effects on both behavior and physiology.

“People often think horses can fully sleep standing up. They can’t,” Dr. Bertone said. “What often leads to sleep disorders is insecurity in the horse’s environment. That can be exacerbated by pain, changes in herd dynamics or even minor environmental changes like switching stalls, moving a companion, or altering lighting. Even something as small as a new light bulb can trigger issues.”

The consequences of sleep deprivation are wide-ranging. Horses may show behavioral changes such as aggression, disorientation or collapsing. Physiologically, poor sleep can affect weight, condition and overall health. In high-performance horses, inadequate rest can impair performance, while properly rested horses maintain weight, show better attitude and recover more efficiently from training or competition. “Staff at racetracks take notice of horses’ rest behavior in the stables and add that to the calculation.”

A nearly universal sign a horse may be suffering from a sleep disorder is scarring on the front of the fetlocks – marks left from collapsing while attempting to rest. Other indicators include unusual aggression, difficulty relaxing in the stall, or collapsing under saddle or restraint. “Those scrapes on the fetlocks are often the first sign owners notice,” Dr. Bertone said.

To better diagnose and treat these cases, Dr. Bertone developed the Equine Sleep Evaluation (EquineSleepDisorders.com), a comprehensive consultation that assesses sleep-related issues in horses. Owners submit detailed information about the horse’s environment, history, training routines and behaviors through a secure online portal, along with video recordings of sleep patterns and concerning episodes. Dr. Bertone analyzes the data, generates a personalized report and collaborates with the horse’s primary veterinarian to create a thorough treatment plan.

“I never advise owners directly on medications, and I always consult with their veterinarians with my thoughts” he said. “It’s essential that the primary veterinarian remains central to the care plan. My role is to provide insight and guidance based on observation and research, while the veterinarian implements any treatment. One very important take-home is there is no universal cure.”

Technology has become critical to his work. Stall cameras and long-term video monitoring allow patterns to emerge over weeks, providing far more insight than short clips. Wearable technologies, motion-sensing blankets and sensor-equipped pads are beginning to provide even deeper understanding of sleep and environmental factors. “Over the next decade, I expect these tools to become more refined and widely accessible, offering unprecedented insight into equine behavior,” he predicted.

Awareness of equine sleep disorders is growing. Over four decades, Dr. Bertone has dealt with more than 1,800 cases from around the world. And that number grows weekly. While these disorders may not be common for the average veterinarian, recognition is increasing thanks to social media and online forums where owners share experiences and seek guidance. In addition, a new young generation of leaders in this area grows.

“Some equine veterinarians may go their entire career without ever seeing one of these cases, while others may see a few,” Dr. Bertone said. But for those horses and their owners, recognizing the problem can be transformative. Even subtle improvements in rest can have major impacts on a horse’s health, behavior and performance.

Dr. Bertone approaches each case methodically, often beginning with a detailed online intake form. The form collects information about herd dynamics, the horse’s age, how long the owner has had the horse and other relevant details. Video guidance is crucial for identifying Sleep Terror Syndrome, a condition where horses lie down at night and wake in a terror, similar to the disorder in humans.

Behavioral factors, especially herd composition, often play a role. “In some cases, all the geldings might be grouped together with no mares present, which can create stress,” Dr. Bertone noted. Adjusting herd dynamics, along with possible medical interventions guided by the veterinarian, often leads to improved outcomes.

Ultimately, Dr. Bertone’s work bridges clinical observation, research and practical veterinary care. He emphasizes that proper rest is fundamental to equine health, yet subtle environmental, social, or physiological stressors can disrupt it in ways owners may not recognize. By combining careful evaluation, long-term monitoring and collaboration with veterinarians, he helps ensure that horses not only survive but thrive.

For horse owners and veterinarians alike, Dr. Bertone’s work offers a crucial lesson. Sometimes the signs are small, such as scrapes on the fetlocks, minor behavioral changes, yet their implications are profound. Sleep is as essential for horses as it is for humans, and understanding it requires a keen eye and dedication. Through decades of research and practice, Dr. Bertone continues to illuminate this overlooked aspect of equine health, offering insight, tools and hope to horses and their caregivers worldwide.

Photo Credits:

istockphoto.com/Prescott Patterson