Epidemiology of Critical Illness in the Elderly

• Caring for the aging population is one of the most important challenges of the twenty-first century. A key component of medical care delivery in the elderly is the provision of critical care services. • In addition to chronologic age, disability, comorbidity, and frailty are components of defining the elderly population. Frailty is a clinical syndrome characterized by multiple factors, including weight loss, fatigue, weakness, low activity level, slow motor performance, balance and gait abnormalities, and cognitive decline. A combination of age, function, and social definitions is key to precisely defining the elderly population. • The demographics of the global and US populations have changed dramatically over the course of the last two centuries as a consequence of demographic transition, which defines a transition in a population from high birth and death rates to low birth and death rates as a result of economic development. • The world population reached 7.3 billion in 2015 and has aged at unprecedented rates. By 2050, the number of elderly in the world will, for the first time in history, be greater than the number of young individuals. • The sharp increase in the US birth rate between 1946 and 1964 is termed the baby boom. This has resulted in a drastic shift in the age distribution of the population. In 2015, the median age in the United States was 37 years, and it is estimated that this will increase to 42 years by 2050. Conversely, the total fertility rate in the United States has been declining and was 1.89 in 2015. Therefore, the growth rate of the elderly population is far higher than that of the younger population. • Chronic medical conditions are expensive to treat. Multimorbidity is the presence of two or more chronic diseases and is common in the elderly, with a prevalence of 40 to 80 percent. It has a substantial impact on mental health, quality of life, and overall health outcomes and is associated with a significant increase in mortality. Disability in the elderly may have an even greater impact on mortality than multimorbidity. • The elderly population comprises an increasing proportion of patients admitted to intensive care units (ICUs), and the mortality rate for these patients is high. Equally important is the significantly decreased physical function and overall health of ICU survivors.