Miguel Meira Cruz, DDS, MSc, PhD, is Director of the Sleep Unit at the Cardiovascular Center of the University of Lisbon (CCUL@RISE), Lisbon School of Medicine, in Lisbon, Portugal. He is a clinician-scientist and educator internationally recognized for pioneering Dental Sleep Medicine in Portugal and for advancing research on the intersection between insomnia, sleep apnea, and cardiometabolic risk. Particularly through the INDEED study of co-morbid insomnia and sleep apnea (COMISA) and their mechanisms. He also directs the European Sleep Center, integrating clinical care, chronobiology, and preventive sleep health. He is the author of the book “The Other Side of Sleep”.
How long have you been practicing sleep medicine?
I have been practicing sleep medicine for about 20 years. I started my Master’s in Sleep Sciences at the Lisbon Faculty of Medicine in Portugal in 2006. At the conclusion I began my practice of sleep medicine with the first sleep consultations in the Department of Stomatology at Portugal’s main hospitals.
Since then, I have worked in clinical practice, academic research, and education. My focus has always been on understanding the complex interactions between sleep, circadian rhythms, and systemic health. Specifically in relation to cardiovascular and metabolic functions and disorders.
You started your career in dentistry; what led you to sleep medicine?
My initial focus was on treating patients with sleep-related breathing disorders. Particularly those who did not meet the criteria for, or were unable to tolerate, continuous positive airway pressure (C-PAP) therapy. At that time, there were few effective alternatives. As a result, many people went untreated. Over time, I noticed that many of my patients experienced sleep difficulties beyond snoring and sleep apnea. Those difficulties influenced their pain, mood, and overall health.
I became increasingly aware of the co-occurrence of sleep disorders such as insomnia and sleep apnea. These disorders are not only harmful on their own, but they can set off a chain of complex interactions with other conditions, killing millions worldwide.
This realization strengthened my motivation to explore ways to prevent and treat combined disorders which would protect patients, families, and communities.
Over the past decade, my focus has been on studying the interaction between insomnia and sleep apnea, a condition known as COMISA. Circadian disruption and psychosocial stress appear to play significant roles. These are the conditions my team and I have been investigating in recent years.
This awareness led me to integrate dentistry with a broader knowledge of sleep medicine and to pioneer a dual approach to treatment in Portugal.
What are the biggest challenges you see for people struggling to sleep?
One of the biggest challenges is fragmentation. People often address symptoms in isolation rather than understanding the biological and psychosocial roots of their sleep problems. Another issue is the chronic exposure to modern stressors. Artificial light, irregular schedules, and digital overstimulation can destabilize circadian timing and harm sleep quality. Many individuals continue to view poor sleep as a minor inconvenience rather than a warning sign of deeper health imbalance. Changing that mindset through education and clinical example is an essential part of our mission.
As if these challenges were not enough, humanity has added another one—the biannual clock change still implemented in several countries around the world also significantly impact sleep. This artificial disruption can cause circadian misalignment, various sleep difficulties, and a wide range of physical and mental health problems. Despite all the evidence and efforts, Portugal, Spain, and many other countries continue to move their clocks each six months. So, for just half the year our schedules align with what nature originally gave us.
In 2019, we published in the European Journal of Internal Medicine the first international consensus on the health implications of clock change. The findings are unequivocal: the transition, especially in spring, is associated with an increased rate of cardiovascular mortality, among other adverse outcomes. And yet, humankind remains stubborn! This is precisely why I insist on research and education; to align our collective behavior with what science and biology have long been telling us.
What about sleep medicine are you most excited about?
I am fascinated by the holistic nature of sleep medicine. It connects biological, psychological, and environmental systems into a unified picture of health.
What excites me most is translating scientific discoveries into clinical strategies. Those strategies can restore equilibrium between sleep, circadian timing, and the body’s self-regulation. Sleep medicine continuously challenges us to bridge the gap between physiology and behavior. Even the smallest improvements in sleep can have profound effects on well-being and longevity.
What is one important thing you want people to know about sleep?
Sleep is the physiological cornerstone that synchronizes the body’s internal systems with the external world. It is not merely a state of rest but a biological reset that protects cardiovascular, metabolic, immune, and emotional health. To care for sleep is to care for life itself. It is the most natural and universal form of medicine.
As clinicians, we are also advocates of rhythm. Our responsibility extends beyond treatment. We must help people realign with the natural cycles of light, activity, and rest that sustain human health. Promoting sleep health means promoting harmony between work and recovery, science and empathy, technology and nature. Through that balance, we can cultivate not only healthier individuals but also healthier societies.