**2. Ageing population: Demographics trends**

Population ageing is progressing rapidly in many industrialized countries. For the world as a whole, the elderly will grow from 6.9% of the population in 2000 to a projected 19.3% in 2050 (Gavrilov & Heuveline, 2003).

Population ageing is a great challenge for the health care systems. As nations age, the prevalence of disability, frailty, and chronic diseases (Alzheimer's disease, cancer, cardiovascular and cerebrovascular diseases, COPD, etc.) is expected to increase dramatically.

Frailty is gaining attention in many fields because it increases the risk of hospitalization, falls, mortality and institutionalization. Geriatricians, gerontologists, and social scientists study frailty to better understand its impacts on health, individuals, and society. Frailty has been considered synonymous of disability or co-morbidity, but it is recognized that it is a biological syndrome identified by decreased reserves in multiple organ systems. The incidence of frailty increases with age, reaching more than 32% in those older than 90 years (Fried et al., 2001). Frailty can be a primary diagnosis, when the state is not associated directly with a specific disease, or a secondary diagnosis when the syndrome occur as a result of an acute event or the end stage of many chronic conditions, including severe congestive heart failure, stroke, chronic inflammatory diseases and dementia. The hospital, which is the "gold standard" for the delivery of acute medical care, is not an ideal environment for frail elderly patients. A new functional impairment and iatrogenic events such as nosocomial infections, pressure sores, falls and delirium are common during hospital stay.

Chronic obstructive pulmonary disease is a major cause of chronic morbidity and mortality. Patients with COPD usually have progressive airflow obstruction that is not fully reversible, which leads to a history of progressive, worsening breathlessness that can impact on daily activities and health-related quality of life. Winter outbreaks of COPD exacerbations, mostly occurring in elderly people with concurrent chronic co-morbidities, often generate dramatic increases in hospital emergency room admission. Such admissions have increased substantially over the past decade, comprising a significant proportion of all hospital admissions, and are associated with a high rate of readmission contributing to the high costs of care for COPD.
