6.4 - The Epidemiological Transition
The concept of epidemiological transition and its impact on disease patterns
The epidemiological transition describes the shift in a country's health profile as it develops economically and socially. This transition moves from a prevalence of infectious or communicable diseases, often termed "diseases of poverty," to non-communicable, degenerative conditions known as "diseases of affluence."
Characteristics of disease patterns in different development stages
- Low-income countries - Expected to have most deaths and illnesses from infectious diseases such as respiratory diseases, measles, and diarrhoea.
- High-income countries (HICs) - Experience more deaths and illnesses from heart attack, stroke, and cancers.
Changes in leading causes of premature death over time
As countries undergo the epidemiological transition, the primary causes of premature death evolve significantly.
Shifts in premature death causes in China (1990 to 2013)
| Rank in 1990 | Cause of premature death | Rank in 2013 | % Change 1990–2013 | Disease type |
|---|---|---|---|---|
| 1 | Lower respiratory infections | 9 | -80% | Communicable, infectious |
| 2 | Cerebrovascular disease | 1 | -5% | Degenerative, non-communicable |
| 3 | Neonatal preterm birth | 14 | -88% | Communicable, infectious |
| 4 | Chronic obstructive pulmonary disease (COPD) | 4 | -30% | Degenerative, non-communicable |
| 5 | Ischaemic heart disease | 2 | -15% | Degenerative, non-communicable |
| 10 | Diarrhoeal diseases | 66 | -92% | Communicable, infectious |
| 15 | Lung cancer | 5 | 55% | Degenerative, non-communicable |
Key observations from the data
- Risk factors in 2013 - Poor diet, high systolic blood pressure, and air pollution were the leading risk factors for premature death in China.
- Demographic specifics - Females aged 28–36 years experienced the greatest reduction in mortality rate from all causes (84%).
The link between population ageing and chronic disease burden
Population ageing is a global phenomenon closely tied to the rise of chronic diseases. As life expectancy increases and fertility rates decline, the proportion of older individuals in a population grows, leading to a higher burden of non-communicable conditions.
Dynamics of population ageing
- High-income countries - Population ageing persists due to sustained low fertility and gradual increases in life expectancy.
- Middle-income countries - Rapid declines in mortality and fertility rates over the 20th century have accelerated population ageing. For instance, the doubling of the over-65 population from 7% to 14% took 46 years in the UK and 68 years in the USA, but is projected to take just 26 years in China and 21 years in Brazil.
- Global epidemic of chronic diseases - Ageing populations are strongly associated with increased prevalence of chronic conditions.
The prevalence of cardiovascular diseases in different income contexts
Cardiovascular diseases, including heart disease, hypertension (high blood pressure), and strokes, become more common during the epidemiological transition.
Patterns of cardiovascular disease prevalence
- General trend in transition - As mortality decreases, nutrition improves, and infections are controlled, high blood pressure, heart disease, and strokes all become more common, with heart disease contributing most to mortality.
- High-income countries - In later stages of development, known as the age of "delayed degenerative diseases," age-adjusted mortality from heart disease declines due to better prevention and treatment.
- Low- and middle-income countries - Heart disease tends to affect individuals at younger ages than in HICs.