👯‍♀️Population and Society Unit 5 – Mortality: Measures, Trends, and Differences

Key Concepts and Definitions

• Mortality refers to the occurrence of death in a population
• Crude death rate (CDR) measures the number of deaths per 1,000 population in a given year
• Age-specific death rate (ASDR) calculates the number of deaths per 1,000 population in a specific age group
• Life expectancy at birth estimates the average number of years a newborn is expected to live based on current mortality patterns
  • Life expectancy can be calculated for different ages (e.g., life expectancy at age 65)
• Infant mortality rate (IMR) measures the number of deaths among infants under one year old per 1,000 live births
• Maternal mortality ratio (MMR) counts the number of maternal deaths per 100,000 live births
• Epidemiological transition describes the shift in leading causes of death from infectious diseases to chronic and degenerative diseases as societies develop

Historical Context of Mortality Studies

• Early mortality studies focused on understanding the impact of infectious diseases and poor living conditions on death rates
• John Graunt's "Natural and Political Observations Made upon the Bills of Mortality" (1662) laid the foundation for modern demography
• The development of life tables in the 19th century allowed for more accurate estimations of life expectancy and mortality patterns
  • Life tables are constructed using age-specific mortality rates and provide a snapshot of a population's mortality experience
• The epidemiological transition theory, proposed by Abdel Omran in 1971, described the shift in causes of death as societies modernize
• Advances in medical knowledge, public health interventions, and improved living standards have contributed to significant declines in mortality rates over time
• The demographic transition theory links changes in mortality and fertility rates to socioeconomic development

Measures of Mortality

• Crude death rate (CDR) provides a general overview of mortality in a population but does not account for age structure differences
• Age-specific death rates (ASDR) allow for more detailed analysis of mortality patterns across different age groups
  • ASDRs are used to construct life tables and calculate life expectancy
• Infant mortality rate (IMR) is a sensitive indicator of overall health and socioeconomic conditions in a population
• Child mortality rate measures deaths among children under five years old per 1,000 live births
• Cause-specific mortality rates calculate deaths due to specific causes (e.g., cancer, heart disease) per 100,000 population
• Potential years of life lost (PYLL) quantifies the burden of premature mortality by considering the years of life lost due to deaths occurring before a given age threshold
• Disability-adjusted life years (DALYs) combine years of life lost due to premature mortality and years lived with disability to measure the overall burden of disease

Global Mortality Trends

• Global life expectancy has increased dramatically since the mid-20th century, from around 48 years in 1950 to over 72 years in 2019
• Infant and child mortality rates have declined significantly worldwide, although disparities persist between developed and developing countries
• The epidemiological transition has shifted the leading causes of death from infectious diseases to non-communicable diseases (NCDs) in most countries
  • NCDs, such as cardiovascular diseases, cancers, and diabetes, now account for over 70% of global deaths
• The HIV/AIDS pandemic has had a significant impact on mortality in many countries, particularly in sub-Saharan Africa
• Advances in medical technology, vaccinations, and public health interventions have contributed to the decline in mortality from infectious diseases
• The "rectangularization" of the survival curve reflects the concentration of deaths in older ages as life expectancy increases

Demographic and Socioeconomic Differences in Mortality

• Mortality rates vary significantly across regions, countries, and subpopulations
• Developed countries generally have lower mortality rates and higher life expectancies compared to developing countries
• Socioeconomic factors, such as income, education, and occupation, are strongly associated with mortality risk
  • Individuals with higher socioeconomic status tend to have lower mortality rates and longer life expectancies
• Gender differences in mortality are observed worldwide, with females generally having lower mortality rates and higher life expectancies than males
  • Biological, behavioral, and social factors contribute to these gender disparities
• Racial and ethnic disparities in mortality exist within countries, often reflecting underlying socioeconomic inequalities and access to healthcare
• Urban-rural differences in mortality are observed, with rural populations often experiencing higher mortality rates due to limited access to healthcare and resources

Causes of Death and Epidemiological Transitions

• The epidemiological transition theory describes the shift in leading causes of death as societies develop
  • The theory proposes three main stages: the age of pestilence and famine, the age of receding pandemics, and the age of degenerative and man-made diseases
• In the early stages of the transition, infectious diseases and malnutrition are the primary causes of death
• As societies develop, improvements in living conditions, nutrition, and public health measures lead to a decline in infectious disease mortality
• In the later stages of the transition, non-communicable diseases (NCDs), such as cardiovascular diseases, cancers, and diabetes, become the leading causes of death
  • Behavioral risk factors, such as smoking, unhealthy diets, and physical inactivity, contribute to the rise in NCDs
• The fourth stage of the transition, the age of delayed degenerative diseases, is characterized by a shift in mortality to older ages and an increase in life expectancy
• The double burden of disease refers to the coexistence of high rates of both infectious diseases and NCDs in some developing countries

Impact of Mortality on Population Dynamics

• Mortality, along with fertility and migration, is a key determinant of population growth and structure
• Declines in mortality rates, particularly infant and child mortality, can lead to rapid population growth if fertility rates remain high
  • This phenomenon is known as population momentum and can contribute to population aging as large cohorts move through the age structure
• Reductions in mortality rates at older ages can lead to population aging, as the proportion of older individuals in the population increases
• The demographic transition theory links changes in mortality and fertility rates to population growth and age structure
  • As mortality rates decline and life expectancy increases, populations experience a period of rapid growth before fertility rates also begin to decline
• The potential support ratio, which measures the number of working-age individuals per older person, can be affected by changes in mortality and population aging
• Mortality patterns can influence population projections and have implications for social and economic policies, such as healthcare and pension systems

Future Challenges and Emerging Issues in Mortality Research

• Population aging presents challenges for healthcare systems, social support networks, and economic growth
• The increasing burden of non-communicable diseases (NCDs) requires targeted prevention and management strategies
• Emerging infectious diseases, such as COVID-19, highlight the ongoing threat of pandemics and the need for robust public health preparedness
• Climate change and environmental degradation may have direct and indirect impacts on mortality, such as through extreme weather events and changes in disease patterns
• Health inequalities within and between countries require attention to ensure equitable access to healthcare and resources
• Advances in medical technology, such as personalized medicine and regenerative therapies, may have implications for future mortality trends
• The integration of big data and machine learning techniques in mortality research can provide new insights into risk factors and interventions
• Ethical considerations surrounding end-of-life care, assisted dying, and the allocation of healthcare resources in the context of population aging and resource constraints