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This lesson examines global patterns of disease, the epidemiological transition model (Omran 1971), the distinction between communicable and non-communicable diseases, and the environmental determinants of health. Understanding the relationship between health outcomes and environmental, social, and economic factors is essential for AQA A-Level Geography Paper 2.
Before analysing patterns, it is important to understand how health is measured at population level:
| Indicator | Definition | Significance |
|---|---|---|
| Life expectancy at birth | Average years a newborn is expected to live | Overall health and development indicator |
| Infant Mortality Rate (IMR) | Deaths under age 1 per 1,000 live births | Sensitive indicator of healthcare quality, nutrition, and sanitation |
| Under-5 Mortality Rate | Deaths under age 5 per 1,000 live births | Broader child health measure |
| Maternal Mortality Ratio (MMR) | Maternal deaths per 100,000 live births | Quality of reproductive healthcare |
| DALYs (Disability-Adjusted Life Years) | Years of healthy life lost to disease or disability | Captures burden of non-fatal conditions |
| Morbidity rate | Prevalence or incidence of disease | Measures illness, not just death |
| Country/Region | Life Expectancy (2023) | IMR (per 1,000) | Key Health Challenges |
|---|---|---|---|
| Japan | 84.8 years | 1.8 | Ageing population, mental health |
| UK | 80.7 years | 3.7 | Obesity, NHS pressures, health inequalities |
| USA | 77.5 years | 5.4 | Obesity, opioid crisis, healthcare inequality |
| India | 70.8 years | 27.4 | Communicable diseases, malnutrition, air pollution |
| Nigeria | 53.9 years | 72.2 | Malaria, maternal mortality, weak healthcare infrastructure |
| Sierra Leone | 54.7 years | 78.5 | Poverty, Ebola aftermath, limited healthcare |
Exam Tip: Health inequalities exist not just between countries but within them. In the UK, life expectancy varies by up to 10 years between the most and least deprived areas (e.g., Blackpool vs. Hart district in Hampshire). Always consider intra-national health inequalities for a more nuanced analysis.
Abdel Omran (1971) proposed the epidemiological transition model, which describes how the pattern of disease changes as a country develops economically and undergoes the demographic transition.
graph LR
S1["Stage 1: Age of<br/>Pestilence & Famine<br/>Infectious disease,<br/>famine, high mortality"] --> S2["Stage 2: Age of<br/>Receding Pandemics<br/>Improved sanitation,<br/>medicine; mortality falls"]
S2 --> S3["Stage 3: Age of<br/>Degenerative & Man-Made<br/>Diseases<br/>Heart disease, cancer,<br/>stroke dominate"]
S3 --> S4["Stage 4: Age of<br/>Delayed Degenerative<br/>Diseases<br/>Medical advances extend<br/>life with chronic conditions"]
| Stage | Name | Dominant Diseases | Life Expectancy | Example |
|---|---|---|---|---|
| 1 | Age of Pestilence and Famine | Infectious diseases: plague, cholera, smallpox, tuberculosis; famine | 20–40 years | Pre-industrial societies; no modern examples |
| 2 | Age of Receding Pandemics | Infectious diseases decline as sanitation, nutrition, and medicine improve | 30–50 years | Parts of sub-Saharan Africa (transitioning) |
| 3 | Age of Degenerative and Man-Made Diseases | Non-communicable diseases: cardiovascular disease, cancer, stroke, diabetes | 50–75 years | UK (mid-20th century), emerging economies |
| 4 | Age of Delayed Degenerative Diseases | Same diseases as Stage 3, but onset delayed by medical advances (statins, chemotherapy, screening) | 75+ years | UK, Japan, most HICs today |
Some scholars have proposed a fifth stage characterised by the re-emergence of infectious diseases (e.g., antibiotic-resistant bacteria, novel pandemics like COVID-19) alongside persistent non-communicable diseases. This concept, sometimes called the Age of Re-emerging Infectious Diseases, reflects:
| Feature | Communicable Diseases (CDs) | Non-Communicable Diseases (NCDs) |
|---|---|---|
| Definition | Diseases caused by pathogens (bacteria, viruses, parasites) that can be transmitted between people or from animals | Diseases not caused by infection and not transmissible between people |
| Examples | Malaria, tuberculosis, HIV/AIDS, cholera, COVID-19 | Cardiovascular disease, cancer, diabetes, COPD, mental illness |
| Transmission | Direct contact, airborne, waterborne, vector-borne | Not transmitted; caused by genetics, lifestyle, environment |
| Geographic pattern | More prevalent in LICs (due to poverty, poor sanitation, limited healthcare) | More prevalent in HICs (due to ageing, diet, sedentary lifestyle) but increasing rapidly in LICs/MICs |
| Prevention | Vaccination, sanitation, mosquito control, hygiene education | Lifestyle changes (diet, exercise, smoking cessation), screening |
Key Definition: A vector-borne disease is one transmitted by an organism (vector), typically an insect. Malaria is transmitted by Anopheles mosquitoes; dengue by Aedes mosquitoes; Lyme disease by ticks.
The relationship between environment and health operates through multiple pathways:
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