[Sleep is the best medicine: what internists should know about sleep and sleep medicine]

Sleep is a fundamental biological function that affects nearly all organ systems, yet it has been insufficiently documented and considered in internal medicine practice to date. The aim of this review is to present the physiological basis of sleep, clinically relevant sleep disorders, and their significance for internal medicine conditions, as well as to outline practical approaches to prevention, diagnosis, and treatment. Sleep deprivation and sleep disorders are associated with an increased risk of hypertension, type 2 diabetes mellitus, obesity, cardiovascular events, and neurodegenerative diseases. Common disorders such as insomnia, obstructive sleep apnea, and circadian dysregulation have close bidirectional interactions with internal medicine conditions. Validated screening instruments such as questionnaires, digital health applications (DiGA), and evidence-based prevention strategies now enable low-threshold, structured care. Sleep is therefore a central but often underestimated health factor in internal medicine. Internists should systematically record sleep, integrate it into treatment planning, and use evidence-based measures. Greater implementation of sleep medicine in prevention and care could contribute significantly to improving patient care.