The share of people with several long-term diseases (multimorbidity) is 37.2% worldwide and is still growing. Living with two or more co-morbidities impairs quality of life, causes functional limitations and shortens life expectancy by nine years in people aged 45 years. Multimorbidity increases the burden on healthcare systems – it leads to more frequent doctor visits, hospitalizations and higher utilization of healthcare. In some disadvantaged groups, multimorbidity appears 10 to 15 years earlier, with prevalence at age 60 in the poorest decile of England being double that of the richest. In low- and middle-income countries, the situation is more serious because of the "double burden" of chronic and infectious diseases. Current healthcare systems are still focused on treating one disease at a time, leading to fragmented care and poor coordination between specialists. This structure is ill-prepared to handle the complexity of patients with multiple illnesses.