The article discusses the challenges of an aging population in developed countries, where life expectancy has increased significantly over the past two centuries. It highlights that most babies born since 2000 in countries with long life expectancies will live to 100 years. The aging process is influenced by low fertility, low immigration, and long lives. Research suggests that aging processes are modifiable, and people are living longer without severe disability. Technological and medical advancements, along with redistribution of work, will be important for meeting the challenges of an aging population. The article reviews mortality trends, noting that life expectancy is increasing linearly in most developed countries. Mortality at older ages has continued to fall, with significant improvements in survival rates for people aged 80 years and older. However, mortality improvements have stagnated in some countries, such as the USA, for older populations. Smoking is a major factor in health disparities, particularly in Denmark. The article also discusses health trends, noting that chronic diseases are increasing in the elderly population. However, there is evidence that disability prevalence is falling, with improvements in mobility and functional limitations. Health expectancies, which combine life expectancy and prevalence of good health, show that people are living longer with less disability. The article also addresses the consequences of mortality, disease, and disability, noting that while people are living longer, they are not necessarily living better. For those aged younger than 85, there is evidence of postponed limitations and disabilities, despite an increase in chronic diseases. For those aged older than 85, the situation is less clear, with sparse data and concerns about the health of exceptionally old people. The article concludes that population aging poses severe challenges for the traditional social welfare state, and that strategies such as raising the retirement age and redistributing work may be necessary to meet these challenges. The article emphasizes the importance of public health efforts to improve the health and longevity of the elderly population.The article discusses the challenges of an aging population in developed countries, where life expectancy has increased significantly over the past two centuries. It highlights that most babies born since 2000 in countries with long life expectancies will live to 100 years. The aging process is influenced by low fertility, low immigration, and long lives. Research suggests that aging processes are modifiable, and people are living longer without severe disability. Technological and medical advancements, along with redistribution of work, will be important for meeting the challenges of an aging population. The article reviews mortality trends, noting that life expectancy is increasing linearly in most developed countries. Mortality at older ages has continued to fall, with significant improvements in survival rates for people aged 80 years and older. However, mortality improvements have stagnated in some countries, such as the USA, for older populations. Smoking is a major factor in health disparities, particularly in Denmark. The article also discusses health trends, noting that chronic diseases are increasing in the elderly population. However, there is evidence that disability prevalence is falling, with improvements in mobility and functional limitations. Health expectancies, which combine life expectancy and prevalence of good health, show that people are living longer with less disability. The article also addresses the consequences of mortality, disease, and disability, noting that while people are living longer, they are not necessarily living better. For those aged younger than 85, there is evidence of postponed limitations and disabilities, despite an increase in chronic diseases. For those aged older than 85, the situation is less clear, with sparse data and concerns about the health of exceptionally old people. The article concludes that population aging poses severe challenges for the traditional social welfare state, and that strategies such as raising the retirement age and redistributing work may be necessary to meet these challenges. The article emphasizes the importance of public health efforts to improve the health and longevity of the elderly population.