CLINICAL NUTRITION

EFFECT OF FAMINE ON LATER MENTAL PERFORMANCE

Prenatal exposure to the severe Dutch famine of 1944-45 appeared to have no effect on the frequency of severe or mild mental retardation, nor on intelligence as measured

by the Raven matrices at age 19.

Key Words: fetus, famine, mental retardation

The relationship between malnutrition and psychological development has attracted increasing attention in the last decade. Evi- dence of this can be seen from the many re- views related to this topic which have appeared in this journal in recent

Clearly this is an important question be- cause the majority of the world’s children suffer from some degree of protein-calorie malnutrition and their subsequent intellec- tual development may be involved. The re- search in laboratories and hospitals in several countries which has been so exten- sively reviewed shows a clear association between malnutrition early in life and sub- sequent be1 ow-average performance both in laboratory animals and in man. Despite the growing literature we still lack “the data to distinguish the particular contributions of early severe malnutrition, adequate en- vironment, and experiential opportunities to defective cognitive function.”

Research in human beings using both retrospective and prospective studies has attempted to relate early malnutrition to later retardation in mental development. Many reviewers have pointed out that these studies have nearly all failed adequately to control for the social deprivations of which poor nutrition is just a part. 7 - 8 The touchy subject of genetic inheritance which also might relate both to nutritional status and intelligence has been relatively shunned in these studies.

Investigations on the relationship of child- hood malnutrition to later intellectual per- formance have relied almost exclusively on subjects who were drawn from economi- cally poor families and who came from relatively deprived homes. This is because that is the environment in which protein- caloric malnutrition is most prevalent.

If the social determinants are to be sepa- rated from dietary factors then studies may need to be conducted on the exceptional cases of malnutrition which occur unre- lated to chronic social and economic depri- vation. The need to use the survivors of severe famines and of conditions such as celiac disease for this type of research has been pointed but only now are the re- sults of such studies becoming available.

One such study reports on the effect of prenatal exposure to the Dutch famine of 1944-45.lO This work is of particular signifi- cance because, using a well conceived re- search design, the results appear to show no effect of the famine on mental performance.

The famine in the Netherlands was man- made, it was sharply circumscribed in both time and place, and the degree of nutri- tional deprivation was well documented. Famines have seldom taken place where such extensive and valid data allowed sub- sequent analysis.

The cause of the famine was a transport embargo by the Nazis on western Holland beginning in September 1944 as a reprisal against the Dutch collaboration in the abor-

740 NUTRITION REVIEWSIVOL. 31. No. WMAY 1973

tive British landing at Arnhem. The famine was restricted to the western part of the country and continued until the Allied ar- mies liberated the area in May 1945.

Records show that poor rations pro- vided a mean of 450 Kcal. at their lowest point, and for six months were below 750 Kcal. per head per day, while in the non- famine areas of the country during thesame period the calories available from food ra- tions did not fall below 1,300 Kcal., and were often higher. Availability of carbohy- drate, fat, and protein was about equally affected .

Death rates in cities in the famine area rose sharply during this period, many deaths were certified as being due to starvation, famine edema was prevalent, and manysub- jects lost as much as 25 percent of their total body weight. Nutrition teams entering after the liberation have adequately con- firmed that this was an extremely se- vere famine and that it was geographically isolated.

The study undertaken was a retrospective cohort study. Birth cohorts of those ex- posed and not exposed to famine were re- constructed using the place and date of birth. Males born between early 1944 and the end of 1946 were divided into separate cohorts according to whether they were conceived or born before, during or after the famine. Approximately 20,000 subjects studied had been “exposed to the famine through maternal deprivation,” that is, they were in utero during part or the whole of the famine.

In Holland all those eligible for military induction, and capable of appearing, are medically examined and psychologically tested routinely at age 18. In this study the three dependent variables were all con- cerned with intellectual performance judged at this examination. These were (1) severe mental retard at i o n (I nternat i onal Classification of Diseases Codes (1 948) 3250 (idiot), 3251 (imbecile) and 3254 (Mon- goloid); (2) mild mental retardation, Code 3252 (debilitas mentis); and (3) intelligence

quotient as measured by the Dutch version of the Raven progressive matrices.

The independent study variable was ex- posure to famine with a postulated modera- tor variable of fetal age at the time of ex- posure. Two confounding variables, notably fertility and social class, were controlled in the analysis.

The results show that the frequency of severe mental retardation among survivors was not related to conception, pregnancy, or birth during the famine. Similarly, rates of mild mental retardation were apparently uninfluenced by the famine. There was a slight rise in frequency of severe mental re- tardation both in famine and control cities during the period. Results from the non- famine control cities in every cohort show higher rates of mild mental retardation there than in the famine cities.

Most important, there was no association in the Raven matrices data with the period of famine. The very poor diets at various stages of pregnancy appeared to have no measurable effect on surviving offspring tested years later with this intelligence test.

Although the authors, with their interest in the fetus, do not point this out, their data suggest that infants who were subject to the famine had, as adults, Raven matrices scores which were not different from those of subjects who were conceived after the end of the famine.

Birth weights were not available for the subjects in the retrospective cohort study, but a comparison was made of 862 single- ton births from hospitals in Rotterdam (fam- ine city) and 851 in Haarlem (control city). This shows a definite association between famine and low birth weights. Those chil- dren born at the end of the famine period in Rotterdam had mean birth weights about 250 g. lower than those born in Haarlem.

A striking finding in the data from this re- search is the differences between mean grouped scores of two social classes, namely families of manual and nonmanual workers. Very significant differences in rates both of mild mental retardation and in

NUTRITION REVIEWS/VOL. 31. No. S/MAY 1973 141

Raven matrices scores were found in the two social classes, and in favor of the non- manual workers. Thus, although no effect on mentality is detectable from the famine, there is a very significant association be- tween the social class of the father, as judged by occupation, and both mental re- tardation and intelligence test scores.

The authors also found evidence of a de- cline in fertility related to the famine. This loss of fertility affected the manuat workers more than the nonmanual workers. The consequence of this for the study was con- trolled for in the analysis.

The results of this study in the Nether- lands are contrary to the research findings from many other countries. However, in nearly all previous investigations the mal- nourished children have all been drawn from low social class populations who suf- fer from many deprivations- including die- tary deficiencies.

There are certainly criticisms that can be leveled against this American study of a Dutch population. These include the fact that nutritional data are based on rations for a population and not on individual in- takes; that the famine and control cities have differences other than exposure to famine; and that the Raven matrices, as an i n tel I igence test, have severe I i m i tat ions. These doubts can be challenged because the study design is good and uses sophisti- cated epidemiological techniques to cir- cumvent these criticisms. For example, the nutritional effects of the famine can be seen in the birth weights; the cohort design al- lows comparisons to be made without relying on the control cities simply by com- paring cohorts, affected and not affected by famine, within the study groups; and the fact that the Raven matrices, as used, proved to be sensitive enough to show very marked differences in scores by social class.

It is fair to conclude from this study that starvation during pregnancy had no detect-

able effect on adult mental performance of surviving male offspring and that a strong association was shown to exist between performance of low and high social class in the same population.

The conclusions from this study do not support the view that severe undernutrition during pregnancy, or low food availability in early infancy, will affect later intellectual development above and beyond social-fa- milial variables. On the contrary, the re- search suggests that the human fetus is not damaged by starvation of the mother in a manner to seriously impair adult perform- ance in the male survivor. At any rate, any impairment is not of a degree that cannot be overcome by standard child-rearing practices as they exist in Holland. It must be remembered, however, that the majority of mothers in the Dutch population were well-nourished prior to the famine period. The results, therefore, are not necessarily applicable to developing countries, where malnutrition and undernutrition are at all times very common, and opportunities to recover from damaging effects of early malnutrition may not be available. 0

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