The quality of life of a person is strongly affected by his or her health status and is an important factor for economic and social performance. Health status is determined to a great extent by the occurrence of long-lasting, i.e. chronic diseases and complaints and by mental health and social wellbeing. Chronic diseases can severely limit the ability to perform everyday activities, and not only impair the quality of life of those affected but may also involve high treatment costs. Self-perceived health enables reliable conclusions to be drawn about the general health status of the population.