Epidemiological Transition Notes

Aging World

  • The world's population is aging, with 10% being 65+ in 2024, totaling 800 million people.
  • The proportion of the world's population over 60 years is expected to increase from 12% to 22% between 2015 and 2050.
  • By 2050, the global population of individuals aged 60 years and older will be approximately 2.1 billion.
  • The number of people aged 80 years or older is projected to triple by 2050, reaching 426 million, according to WHO forecasts.
  • Population aging, which is the shift in a country's population distribution towards older ages, began in high-income countries (e.g., Japan, where 30% of the population is already over 60 years old).
  • Low- and middle-income countries are now experiencing the most significant changes related to aging populations.
  • By 2050, 80% of older people will reside in low- and middle-income countries.
  • An aging world requires proactive planning rather than concern.
  • All countries face challenges in ensuring their health and social systems can manage the anticipated demographic shift.
  • Population aging presents challenges like a shift in the burden of disease towards more chronic conditions such as hypertension and diabetes and an increased demand for caregiving.
  • Primary Health Care (PHC), including preventive measures, is crucial for delaying the onset of age-related diseases and maintaining older adults' health, which reduces the long-term burden on health systems.

Demographic Transition Model

  • The Demographic Transition Model represents the transition from high birth and death rates to low birth and death rates as a country develops from a pre-industrial to an industrialized economic system.
  • It is a tool for determining a country's economic development using demographic statistics.
  • Stage 1: High birth and death rates result in low and fluctuating population growth.
  • Stage 2: The birth rate remains high, while the death rate falls, leading to high population growth.
  • Stage 3: The birth rate starts to fall, and the death rate continues to decline, resulting in moderate population growth.
  • Stage 4: Both birth and death rates are low, leading to very low population growth.
  • Stage 5: The birth rate is slightly falling, and the death rate is steady, causing a slow population decrease.
  • Stage 1: High stationary
    • Birth rate: High
    • Death rate: High
    • Natural increase: Slow increase
    • Example: A few remote groups
    • Reasons for changes in birth rate: Many children needed for farming. Many children die at an early age. Religious/social encouragement. No family planning.
    • Reasons for changes in death rate: Disease, famine. Poor medical knowledge so many children die.
  • Stage 2: Early expanding
    • Birth rate: High
    • Death rate: Falls rapidly
    • Natural increase: Very rapid increase
    • Examples: Egypt, Kenya, India
    • Reasons for changes in birth rate: Many children needed for farming. Many children die at an early age. Religious/social encouragement. No family planning.
    • Reasons for changes in death rate: Improvements in medical care, water supply and sanitation. Fewer children die.
  • Stage 3: Late expanding
    • Birth rate: Falling
    • Death rate: Falls more slowly
    • Natural increase: Increase slows down
    • Examples: Brazil
    • Reasons for changes in birth rate: Improved medical care and diet. Fewer children needed.
    • Reasons for changes in death rate: Improvements in medical care, water supply and sanitation. Fewer children die.
  • Stage 4: Low stationary
    • Birth rate: Low
    • Death rate: Low
    • Natural increase: Stable or slow increase
    • Examples: France and UK
    • Reasons for changes in birth rate: Family planning. Good health. Improving status of women. Later marriages.
    • Reasons for changes in death rate: Good health care. Reliable food supply.
  • Stage 5: Declining
    • Birth rate: Very low
    • Death rate: Stable or slow increase
    • Natural increase: Slow decrease
    • Examples: Germany
    • Reasons for changes in birth rate: Family planning. Good health. Improving status of women. Later marriages.
    • Reasons for changes in death rate: Good health care. Reliable food supply.
  • Population Pyramid Shapes:
    • Stage 1: High birth rate. Rapid fall in each upward age group due to high death rates. Short life expectancy.
    • Stage 2: Still high birth rate. Fall in death rate as more living in middle age. Slightly longer life expectancy.
    • Stage 3: Declining birth rate and declining death rate. More people living to an older age.
    • Stage 4: Low birth rate and low death rate. High proportion of dependents. Longer life expectancy.
    • Stage 5: Birth rate is less than the death rate, increasing old age. Population is declining.

Epidemiology

  • Epidemiology is a branch of medical science that studies the distribution of disease in human populations and the factors that determine its distribution, principally by using statistics.

Epidemiologic Transition Theory

  • 1971, Abdel Omran introduced the Epidemiologic transition theory which describes the stages of development that are characterized by a shift in population growth, life expectancy, and disease patterns.
  • It describes the process by which the pattern of mortality and disease is transformed from one of high mortality among infants and children, episodic famine and epidemic affecting all age groups to one of degenerative and man-made diseases (such as those attributed to smoking) affecting principally the elderly.
  • The Epidemiological transition occurs over timescales spanning decades or centuries.
  • Reduction in mortality is followed by a reduction in fertility.
  • Increased proportion of aging population.
  • Less malaria, diarrhoeal diseases, TB and HIV/AIDS.
  • More non-communicable diseases; cardiovascular diseases, cancer, COPD, road traffic accidents and diabetes mellitus.
  • Changes in burden of disease from communicable to non-communicable diseases.

Stages of Epidemiologic Transition

  • Stage I: Pestilence and Famine
    • Infectious and parasite diseases were principle causes of death along with accidents and attacks by animals and other humans.
    • Most violent Stage I epidemic was the Black Plague(black death) probably transferred to humans by fleas from infected rats.
    • 25 million Europeans died between 1347 to 1350.
  • Stage II: Receding Pandemics
    • Improved sanitation, nutrition, and medicine during the Industrial Revolution reduced the spread of infectious diseases.
    • Death rates did not improve immediately and universally during the early years of the Industrial Revolution.
    • Poor people who crowded into Industrial Cities had high death rates due to cholera, due to acute diarrhea and vomiting that can kill within hours if left untreated.
  • Stage III: Degenerative Diseases
    • Associated with the chronic diseases of aging.
    • Cardiovascular diseases and cancer.
    • Sub-Saharan Africa and South Asia have low incidences of cancer primarily because of low life expectancy.
  • Stage IV: Delayed Degenerative
    • Life expectancy of older people is extended through medical advances.
    • Cancer medicines, bypass surgery and better diet.
    • Consumption of non-nutritious food and sedentary behavior have resulted in an increase in obesity in this stage.
  • Stage V
    • Reemergence of infectious and parasitic diseases; diseases thought to have been eradicated or controlled return, and new ones emerge
  • 3 Possible Reasons for Stage V
    • Evolution – new strains due to drug resistance (malaria)
    • Poverty- more infections due to unsanitary conditions (TB)
    • Increased globalization – spread through relocation diffusion (H1N1/swine, severe acute respiratory syndrome (SARS) and COVID-19.
  • This shift is caused by:
    • The aging of the population, because non- communicable diseases affect older adults at the highest rates
    • Improvements in medical care, which mean that children no longer die from malnutrition or from easily curable conditions such as diarrhea.
    • Public health interventions such as vaccinations and the provision of clean water and sanitation, which reduce the incidence of infectious diseases.
    • This pattern can be observed across many countries, with wealthy countries further advanced along this transition.
  • Leading causes of death globally:
    • 2000:
      1. Ischaemic heart disease
      2. Stroke
      3. Chronic obstructive pulmonary disease
      4. Lower respiratory infections
      5. Neonatal conditions
      6. Trachea, bronchus, lung cancers
      7. Alzheimer's disease and other dementias
      8. Diarrhoeal diseases
      9. Diabetes mellitus
      10. Kidney diseases
    • 2019:
      1. Ischaemic heart disease
      2. Stroke
      3. Chronic obstructive pulmonary disease
      4. Lower respiratory infections
      5. Neonatal conditions
      6. Trachea, bronchus, lung cancers
      7. Alzheimer's disease and other dementias
      8. Diarrhoeal diseases
      9. Diabetes mellitus
      10. Kidney diseases
  • Leading causes of death in low-income countries:
    • 2000:
      1. Neonatal conditions
      2. Lower respiratory infections
      3. Ischaemic heart disease
      4. Stroke
      5. Diarrhoeal diseases
      6. Malaria
      7. Road injury
      8. Tuberculosis
      9. HIV/AIDS
      10. Cirrhosis of the liver
    • 2019:
      1. Neonatal conditions
      2. Lower respiratory infections
      3. Ischaemic heart disease
      4. Stroke
      5. Diarrhoeal diseases
      6. Malaria
      7. Road injury
      8. Tuberculosis
      9. HIV/AIDS
      10. Cirrhosis of the liver
  • Leading causes of death in lower-middle-income countries:
    • 2000:
      1. Ischaemic heart disease
      2. Stroke
      3. Neonatal conditions
      4. Chronic obstructive pulmonary disease
      5. Lower respiratory infections
      6. Diarrhoeal diseases
      7. Tuberculosis
      8. Cirrhosis of the liver
      9. Diabetes mellitus
      10. Road injury
    • 2019:
      1. Ischaemic heart disease
      2. Stroke
      3. Neonatal conditions
      4. Chronic obstructive pulmonary disease
      5. Lower respiratory infections
      6. Diarrhoeal diseases
      7. Tuberculosis
      8. Cirrhosis of the liver
      9. Diabetes mellitus
      10. Road injury
  • Leading causes of death in upper-middle-income countries:
    • 2000:
      1. Ischaemic heart disease
      2. Stroke
      3. Chronic obstructive pulmonary disease
      4. Trachea, bronchus, lung cancers
      5. Lower respiratory infections
      6. Diabetes mellitus
      7. Hypertensive heart disease
      8. Alzheimer's disease and other dementias
      9. Stomach cancer
      10. Road injury
    • 2019:
      1. Ischaemic heart disease
      2. Stroke
      3. Chronic obstructive pulmonary disease
      4. Trachea, bronchus, lung cancers
      5. Lower respiratory infections
      6. Diabetes mellitus
      7. Hypertensive heart disease
      8. Alzheimer's disease and other dementias
      9. Stomach cancer
      10. Road injury
  • Leading causes of death in high-income countries:
    • 2000:
      1. Ischaemic heart disease
      2. Alzheimer's disease and other dementias
      3. Stroke
      4. Trachea, bronchus, lung cancers
      5. Chronic obstructive pulmonary disease
      6. Lower respiratory infections
      7. Colon and rectum cancers
      8. Kidney diseases
      9. Hypertensive heart disease
      10. Diabetes mellitus
    • 2019:
      1. Ischaemic heart disease
      2. Alzheimer's disease and other dementias
      3. Stroke
      4. Trachea, bronchus, lung cancers
      5. Chronic obstructive pulmonary disease
      6. Lower respiratory infections
      7. Colon and rectum cancers
      8. Kidney diseases
      9. Hypertensive heart disease
      10. Diabetes mellitus

Primary Health Care (PHC)

  • About 50% of the world’s population lacks access to good primary health care.
  • PHC is a platform for integrated health service delivery to meet people’s changing needs at every age: such as pregnancy care, childhood immunizations, and care for noncommunicable diseases like high blood pressure (hypertension).
  • PHC supports people to live longer, healthier lives
  • Investments to scale up access to quality PHC across low- and middle-income countries can prevent as many as 60 million deaths by 2030 and average life expectancy could increase by 3.7 years.
  • To realize this, we must ensure quality PHC that is centered on people and is continuous, comprehensive, and coordinated to meet their evolving health needs at all stages of life.
  • WHO, World Health Statistics 2024