The demographic transition shows death rates falling. The epidemiological transition, described by the physician Abdel Omran in 1971, asks what people die of at each stage.
Key idea
As countries develop, the main causes of death shift from infectious diseases, famine and childbirth (spread by germs, bad water and poor nutrition) to chronic and degenerative diseases such as heart disease, stroke and cancer, which strike mostly older people.
| Stage | Main causes of death | Matches DTM |
|---|---|---|
| 1 Pestilence and famine | Infectious diseases, famine, parasites; many children die | stage 1 |
| 2 Receding pandemics | Clean water, sewers and better food cut epidemics | stage 2 |
| 3 Degenerative and human-created diseases | Heart disease, cancer, stroke; most people reach old age | stage 3 |
| 4 Delayed degenerative diseases | The same diseases, but treated longer; life expectancy rises further | stage 4 |
| 5 Reemergence (added by some) | Old and new infectious diseases return through travel, drug resistance and poverty | stage 4 or 5 |
Why it works
Infectious diseases kill people of every age, especially babies and children. Clean water, sewers, vaccines, antibiotics and better food prevent most of those deaths. People then live long enough that the diseases of old age become the leading causes. Everyone dies of something, and in a country where few die young, that something is usually a chronic disease.
Worked examples
Worked example: Placing a pattern
In a country, the top causes of death are heart disease, stroke and cancer, and life expectancy is over 80. Which stage?
- Chronic, degenerative diseases lead.
- Life expectancy is very high, so they strike late in life.
Answer: Stage 4 (delayed degenerative diseases).
Worked example: Why cholera faded
Cholera spreads through dirty water. Why did it stop being a leading cause of death in many cities?
- Cities built clean water supplies and sewers in the 1800s and 1900s.
- Without dirty water, cholera could not spread.
- That is the move from stage 1 to stage 2.
Answer: Clean water and sewers cut its spread.
Common mistake
Students think chronic diseases became common because people became less healthy. Mostly they lead because people now live long enough to get them. A disease of old age cannot be common where few reach old age. Diet and smoking matter too, but the main reason is that the deaths of the young have been prevented.