Tuesday September 14 2010
The study examined an extreme wartime famine
Extreme World War II food shortages may have affected the brains of babies in the womb, BBC News reported. The website said that a study of Dutch adults found that performance in mental tests was weaker in people whose mothers were pregnant with them during times of severe rationing.
The study found that “selective attention”, the ability to concentrate and ignore distractions, was poorer in men and women whose mothers were exposed to famine during the early stages of pregnancy. However, their performance in several other tests was no worse than that of children whose mothers were well nourished.
Although the findings of this study are of general interest, the small numbers of participants involved and inconsistent findings mean the research cannot prove that famine exposure in the womb leads to reduced mental functioning. Also, the food shortages involved were far more extreme than anything modern mothers would face and should not be seen as a cause for concern.
Where did the story come from?
The study was carried out by researchers from the University of Amsterdam and Calvin College, Michigan. It was published in the peer-reviewed journal Proceedings of the National Academy of Sciences. It was funded by several research centres, including the Netherlands Heart Foundation, UK Medical Research Council and European Science Foundation.
The research was covered accurately and in some detail by the BBC’s news report, which featured guidance from independent experts that the study should not cause alarm for modern mothers.
What kind of research was this?
This cohort study investigated aspects of mental performance in middle-aged men and women who had been exposed to wartime famine conditions while they were in the womb. Their performance was compared to people who were not exposed to these conditions.
The researchers point out that during the winter of 1944-45, a severe famine – the Hunger winter – struck the cities in the western part of the Netherlands. It was caused by an embargo on food transport by the occupying German army. For five to six months, daily rations dropped to as little as 400 to 800 calories a day, well below today’s recommended intake of 2,000 calories for women and 2,400 calories for men.
The authors say that a previous study of 19-year-old conscripts, published in 1972, found that prenatal exposure to the famine had no effects on their reasoning ability or on rates of mental retardation. However, a more recent study by some of the same researchers suggested that prenatal exposure to the famine increased the risk of heart disease and diabetes in people in their 50s. Since both these diseases are associated with ageing, the researchers suggested that exposure to the famine while in the womb may also lead to an age-associated decline in mental function in later life.
What did the research involve?
The researchers used an ongoing study, called the Dutch Famine Birth Cohort, which consists of men and women who were born at a teaching hospital in Amsterdam between 1943 and 1947. From this study, the researchers recruited 860 participants aged 56 to 59. The researchers used records of official daily food rations to investigate prenatal exposure to famine, which was defined as a mother’s average daily food ration containing fewer than 1,000 calories during any 13-week period. They also analysed calorie intake in 16-week blocks to differentiate between the early, middle and late periods of gestation.
Between 2002 and 2004, the researchers measured several aspects of mental function in the study’s participants. This included a general intelligence test, a memory task and a task to measure motor skill, such as copying a shape. Participants also completed a task to measure selective attention (the ability to concentrate and ignore distractions). In this last test, people were presented with the name of a colour printed in one of four different ink colours (for example, the word “blue” printed in yellow) and were asked to name the colour of the ink rather than read the written word.
The researchers also collected other information from participants, including information on their education, medical history, use of medication, lifestyle and head circumference. Using standard statistical techniques, they compared the results of those who had been exposed to famine while in the womb and those who had not.
What were the basic results?
Of the 737 people who finally took part, 40% had been exposed to famine in the womb. The researchers found that:
- People exposed to famine in the womb performed worse on the “selective attention” task than those who were not exposed.
- The effect on selective attention was statistically significant in those who were exposed to famine during early pregnancy (the first 16 weeks).
- Adjusting for potential confounders minimally changed this association.
- The effect of early famine exposure on this task was comparable to the effect of other factors such as gender and education, and was more than twice as large as the effect of smoking.
- Prenatal famine exposure was not associated with poorer performance in the other tests of mental ability.
The researchers also found that people who had been exposed to famine during any stage of gestation had smaller head circumferences at age 56-59.
How did the researchers interpret the results?
The authors say that maternal malnutrition during foetal development may have a negative effect on certain aspects of mental ability in later life, and that this may be associated with early ageing.
This study found that people who had been exposed to famine while in the womb performed less well on one test of mental function than a comparable group of people who had not been exposed to famine. It should be noted that, while the researchers tried to take into account potential confounders, other environmental or genetic factors may have influenced the results of this study. Also, poor performance on a single test of selective attention, tested on only a single occasion, gives little indication of a person’s overall cognitive function and does not conclusively demonstrate early ageing.
As the authors point out, the study has other limitations, such as:
- The sample of participants was small, with only 64 people exposed to famine during the early part of pregnancy. This means that the observed effect could have been due to chance.
- Only about 60% of eligible cohort members participated, which could be a source of bias if there were differences between those who chose to participate and those who declined.
- It is possible that other factors, such as maternal stress, caused the difference in performance.
In summary, although this study is of general interest, there is a need for further research involving repeated testing on a larger number of people before any conclusions can be drawn as to whether prenatal famine exposure accelerates ageing processes, such as loss of concentration.
Expectant mothers should not be concerned by these findings, which are based on an analysis of extreme wartime famine. As Fiona Ford, spokesperson for the British Dietetic Association, told BBC News: “The malnutrition would have to be pretty bad - with food intake at incredibly low levels, and there is evidence that the body is capable of adapting in these circumstances to protect the baby."