Ageing and the epidemiology of multimorbidity.

The world's population is ageing and an important part of this demographic shift is the development of chronic illness. In short, a person who does not die of acute illnesses, such as infections, and survives with chronic illnesses is more likely to develop additional chronic illnesses. Chronic respiratory diseases are an important component of these diseases associated with ageing. This article reviews the relationship between ageing and chronic respiratory disease, and also how certain chronic diseases cluster with others, either on the basis of underlying risk factors, complication of the primary disease or other factors, such as an increased state of inflammation. While death is inevitable, disabling chronic illnesses are not. Better understanding of how individuals can age healthily without the development of multiple chronic illnesses should lead to an improved global quality of life.