He continued to specialize in Sleep Medicine through Master's programs in Sleep: Physiology and Medicine at the Pablo Olavid University of Seville, a Diploma in Sleep Medicine from the Stanford School of Sleep Medicine, and Certification in Sleep Medicine from the Royal College of Edinburgh. He collaborated for about a decade with the Electroencephalography and Clinical Neurophysiology Center (CENC-Sleep Center), the Sleep Units of Luz Amadora Hospital and Setúbal, and started sleep consultations in the Stomatology services of Santa Maria Hospital in Lisbon and São João Hospital in Porto. He coordinated the Sleep Unit of Soerad Hospital in Torres Vedras (2008-2018) and founded the European Sleep Center, which he currently directs.

He is a European Specialist (by the European Sleep Research Society) and an International Specialist (by the World Sleep Society) in Sleep Medicine.

In the stomatological field, he practices clinical work mainly in oral surgery/Implantology and sleep. He is Diplomate by the European Academy of Dental Sleep Medicine (Entry Level), American Academy of Dental Sleep Medicine, and Brazilian Sleep Association (and Brazilian Association of Sleep Dentistry).

He was an Anatomy assistant at Ribeiro Sanches School of Health, and assistant of Histology and Embryology and Human Physiology at the Institute of Health Sciences-South and at Egas Moniz School of Health. Since 2007, he has been part of the team of research collaborators at the Physiology Institute of the Faculty of Medicine of Lisbon.

He is currently the Director of the Sleep Unit at the Cardiovascular Center of the University of Lisbon, in the Faculty of Medicine, and remains as a Free Lecturer at the University Clinic of Cardiology of the same faculty. He is a Lecturer in the Department of Diagnostic Sciences at Tufts University in Boston, USA, and a Guest Professor of Sleep Medicine at the Bahiana School of Medicine and Public Health and at São Leopoldo Mandic Faculty, respectively in Salvador and Campinas, Brazil.

Miguel Meira e Cruz coordinates the Postgraduate Course in Clinical Chronobiology and Sleep Medicine at the Higher School of Health of Alto do Ave, in Famalicão, Portugal.

In the academic-scientific field, he is part of the Board of the World Dentofacial Sleep Society and is a member of the Brazilian Association of Narcolepsy and Idiopathic Hypersomnia, as well as the Scientific Committee of the American Academy of Dental Sleep Medicine. He is a Member of the International College of Dentists and was President of the Portuguese Association of Chronobiology and Sleep Medicine (2013-2021), Vice-President of the Ibero-American Society of Oral Sleep Medicine (since 2020), Founding Member of the Society of Behavioral Sleep Medicine (2011), and a Member of the Board of the Portuguese Association of Oral Sleep Medicine (2009-2011).

He is an Editor, Consultant, and Member of the Advisory and Editorial Board of several peer-reviewed journals. He has published over 100 articles, including about 55 indexed ones, and has presented over 400 lectures/coordination in national and international meetings.

His main areas of interest converge in insomnia, respiratory sleep disorders, movement disorders during sleep, and their interaction, particularly with cardiovascular and metabolic risk. He introduced routine therapy with oral mandibular advancement devices for the control of respiratory sleep disorders in Portugal (2006) and was a pioneer in the study of Comorbidity between Insomnia and Sleep Apnea in pediatric age, validating some important instruments for evaluation and diagnosis of this interaction, particularly in the context of cardiometabolic disease and chronic pain.