Network medicine, multimorbidity and the lung in the elderly.

Noncommunicable diseases, including cardiovascular, metabolic and respiratory diseases, among others, are the major medical challenge of the 21st century. Most noncommunicable diseases are related to the ageing process and often co-occur in the same individual. However, it is unclear whether the index disease is somehow influencing the development of the other ones (comorbidity) or whether all of them (including the index disease) simply represent the clinical expression of pathological ageing (multimorbidity). The pathobiology of ageing, chronic obstructive pulmonary disease (COPD) and concomitant disorders is complex. A new field of research, known as systems biology if applied to model systems or network medicine if applied to human beings, has emerged over the past decade or so, to address biological complexity in a holistic, integrated way. It offers, therefore, great potential to decipher the relationship between ageing, COPD and comorbidities/multimorbidities. In this State of the Art review we present the basic concepts of systems biology, use some examples to illustrate the potential of network medicine to address complex medical problems, and review some recent publications that show how a systems-based research strategy can contribute to improve our understanding of multimorbidity and age-related respiratory diseases.