NLM5008 Chap.3 The Dutch and Chinese Famines as Natural Experiments
The Dutch and Chinese Famines as Natural Experiments
Why famines test the hypothesis
Low birth weight is linked to heart disease, hypertension, type 2 diabetes and stroke, but the famine lecture stresses that programming can occur without any visible change at birth. Testing it needs an exposure that is sharp, dated and imposed from outside.
The Dutch famine of 1944 to 1945 struck a previously well-nourished population in a defined region of the western Netherlands, with an abrupt start and end, a peak from February to April 1945 and daily rations falling from 1,500 to 1,800 kcal to between 400 and 800 at the worst, before recovering after liberation in May 1945.
Timing sorted the outcomes
The lecture's central table sorts long-term effects by the stage of gestation exposed.
Early exposure is linked to obesity, coronary heart disease, glucose intolerance, altered lipids, schizophrenia, heightened stress sensitivity and, in women, breast cancer; mid-gestation exposure to glucose intolerance, kidney dysfunction and obstructive airways disease; late exposure to glucose intolerance and lower birth weight.
The obesity study of about 300,000 military recruits at age 19 found opposite results for early and late exposure, explained by the timing of appetite centre development and fat cell formation.
China and a midlife lifestyle
The Great Chinese Famine of 1959 to early 1961 was larger, longer and more varied in severity.
In the 4C cohort of 77,925 adults free of diabetes at baseline, people exposed before birth had a raised adjusted risk of diabetes, while childhood exposure did not survive adjustment for age.
Among fetal-exposed adults, those with two or more ideal cardiovascular health metrics in midlife showed no significant increase in risk.
A natural experiment is not a trial
The lecture's last table grades the weaknesses of both famines: age and cohort differences between compared groups, exposure classified from geography and severity, survivor selection and the environment after the famine.
The Chinese famine carries more marks on almost every row. The questions left open are whether the exposure was nutrition alone, whether it was measured for individuals, and whether the results generalise.
What this chapter covers
- 01
Birth weight as a marker and programming without it
- 02
The Dutch famine's timing, place and ration record
- 03
Outcomes by early, mid and late gestational exposure
- 04
Obesity at 19 and schizophrenia after early exposure
- 05
The Chinese famine, diabetes and ideal cardiovascular health
- 06
Why a natural experiment is not a randomised trial
Worked example · free
Explaining why early and late exposure pointed in opposite directions
- 2Name the process active in early and mid pregnancy.
- 2Name the process active late in pregnancy and infancy.
Key terms
- Catch-Up Growth
- Accelerated growth after birth in a baby whose growth was restricted in the womb.
- Survivor Selection
- Bias arising because only people who survived an exposure can be studied later.
- Ideal Cardiovascular Metrics
- Health factors such as non-smoking, healthy BMI, activity, diet and blood pressure scored as ideal or not.
- Gestational Timing
- The stage of pregnancy at which an exposure occurs, which decides the process it acts on.
- Risk Ratio
- The risk of an outcome in an exposed group divided by the risk in an unexposed group.
The Dutch and Chinese Famines as Natural Experiments FAQ
What makes the Dutch famine a natural experiment?
Hunger was imposed by war on a previously well-nourished population, in a defined area, with an abrupt start and end, and rations were recorded. Birth dates therefore tell researchers which trimester each person was exposed in, without anyone assigning hunger deliberately.
Did famine exposure always lower birth weight?
No. Only late gestational exposure was linked to lower birth weight, yet early exposure was linked to the widest range of adult conditions. That is why the lecture insists programming can happen without any obvious change at birth.
What did the Chinese famine study add?
Scale and a modifiable second step. In a large Chinese cohort, fetal exposure raised the adjusted risk of diabetes, and among those exposed before birth the increase was confined to adults with one or no ideal cardiovascular health metrics, so midlife lifestyle modified the early risk.
Why is the Chinese famine weaker evidence than the Dutch famine?
It had no sharp start or end, so exposure is inferred from birth year and province, groups compared differ in age, and the environment after the famine varied far more. The lecture's comparison table marks the Chinese famine more heavily on almost every weakness.
Was the famine exposure only about nutrition?
The lecture leaves that open. A famine also brings stress, cold and illness, so part of any effect may come from those rather than from nutrition alone, which is one reason famine findings are treated as supportive rather than conclusive.
Assessment move
Rebuild the lecture's weakness table from memory with both famines as columns, then add the open questions beneath it. Being able to list the weaknesses is worth more in the quizzes than remembering any single ratio.
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