London, April 16 (Inditop) A pandemic of the disease called Hong Kong flu killed more than 700,000 people worldwide in the late sixties, with major outbreaks in Europe during the winter of 1969-70. A new study now shows that early prenatal exposure to the flu may also have caused stunted intelligence in adulthood.
“This is the first report of a possible association between prenatal exposure to an influenza virus epidemic and the mean level of intelligence in the general population,” said Willy Eriksen of the Norwegian Institute of Public Health (NIPH), co-author of a new study on the subject.
The study involved records of more than 180,000 males born between 1967 and 1973 who served in the military.
Military service is compulsory for young men in Norway, who are evaluated medically and psychologically before they enter the service.
The intelligence test data used in the study consisted of a composite score from arithmetic, word similarity and figures tests similar to those commonly used in intelligence tests.
The results showed that the mean intelligence score increased in every birth year from 1967 to 1973, except for a downturn in 1970, said a NIPH release.
The intelligence scores of men born in July through October of that year, six to nine months after the main outbreak of the flu in Norway, were lower than the mean values for those born in the same months during the preceding and following years.
As the flu outbreak occurred during winter months, this suggests that exposure during the first three to four months of pregnancy seems to have had the strongest impact on intelligence scores.
The study was published in Annals of Neurology.
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