Prenatal Hong Kong flu linked to lower IQ

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OSLO, Norway, April 16 (UPI) -- Early prenatal exposure to the Hong Kong flu may interfere with brain development and cause reduced intelligence, researchers in Norway say.

Study co-author Dr. Willy Eriksen of the Norwegian Institute of Public Health said the mean intelligence score increased in every birth year from 1967-1973, except for a downturn in 1970.

The intelligence scores of men born in July through October of that year, 6-9 months after the main outbreak of the Hong Kong flu in Norway, were lower than the mean values for those born in the same months during the preceding and following years.

Eriksen said that study involved records of more than 180,000 men born between 1967-1973 who served in the military in Norway. Military service is compulsory for young men in Norway, who are evaluated medically and psychologically before they enter the service.

The authors suggest that that if 20 percent of the men born between July-October 1970 were exposed to the flu virus -- and assuming they were all affected neurologically -- prenatal exposure to such a virulent virus may reduce intelligence scores by three to seven points on a standard IQ scale.

The study is published in Annals of Neurology.