Chronic diseases (CD) are characterized by long-lasting or persistent symptoms that can affect various parts of the body. They often lead to psychosocial stress situations. CDs require ongoing attention, also in the sense of chronic care. To assess the societal and economic burden, chronic diseases are tracked using various epidemiological approaches, such as primary surveys or secondary data analyses from health insurance providers. The extent and distribution of diseases in a population are reflected by their numerical occurrence (frequency or prevalence), the measurement of which should always be critically examined. Depending on the population group, and when considered separately by age and gender, the prevalence of chronic diseases among people in Germany is estimated to range from 5% to over 90%. Prevention and medical care, both in the sense of chronic care, are of great importance.