Iodine deficiency impairs intellectual and neuromotor development in apparently-normal persons. A study of rural inhabitants of north-central China.
Intelligence was measured by means of the Hiskey-Nebraska Test of Learning Aptitude or the Griffiths Mental Development Scales in a sample of 369 patients from iodine-deficient rural villages (Baihuyao), iodine-sufficient rural villages (Huanglo) and urban populations to test for the damaging effects of iodine deficiency on the development of the nervous system in the presumed healthy section of a community. In urban school-children who were aged seven to 14 years (n = 78), a normal range of measured intelligence was found (mean +/- SD intelligence-quotient score, 107.0 +/- 18.3). By comparison, intelligence-quotient scores were lower in all rural cohorts (a rural suppression effect) but the distribution of intelligence-quotient scores showed a further shift to the left in the iodine-deficient township. In Baihuyaon villagers who were aged 30-35 years (n = 50), who were born during the period of severe iodine deficiency, 72% of villagers had an intelligence-quotient score of less than 70 compared with 41% (P less than 0.05) of villagers who were aged 28-35 years from Huanglo, a rural iodine-sufficient control group (n = 49). Although measured intelligence was higher in Baihuyaon children whose mothers had received iodized salt - 44% of seven- to 14-year-old children had intelligence-quotient scores of less than 70 (n = 141)--it remained significantly depressed compared with rural (n = 51) and urban (n = 78) control subjects (18% and 4%, respectively). These findings were consistent with other parameters (that is, the persistently-high rate of goitre), which indicated that the salt-iodization programme was inadequate. In the iodine-deficient village, lower intelligence-quotient scores showed a relationship with the detection by audiometry of nerve deafness and with the presence of abnormal neurological signs. The latter included spasticity and pyramidal signs which were of a similar pattern to the neurological deficits that have been demonstrated in overt neurological cretins. We conclude that iodine deficiency imposes a further suppressive effect on the intellectual performance of rural inhabitants, and results in a shift of the entire population distribution of cognitive skills to a lower level.
Boyages
S C
SC
Westmead Hospital, NSW 2145.
Collins
J K
JK
Maberly
G F
GF
Jupp
J J
JJ
Morris
J
J
Eastman
C J
CJ
D000293:Adolescent; D000328:Adult; D001299:Audiometry; D002648:Child; D002681:China; D003072:Cognition Disorders / Q000453:epidemiology / Q000209:etiology* / Q000378:metabolism; D015331:Cohort Studies; D003409:Congenital Hypothyroidism / Q000453:epidemiology / Q000209:etiology; D005260:Female; D006042:Goiter / Q000453:epidemiology / Q000209:etiology; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis / Q000209:etiology; D006801:Humans; D007360:Intelligence / Q000187:drug effects*; D007361:Intelligence Tests; D007455:Iodine / Q000172:deficiency* / Q000627:therapeutic use / Q000652:urine; D008297:Male; D011193:Potassium Iodide / Q000627:therapeutic use; D011596:Psychomotor Disorders / Q000453:epidemiology / Q000209:etiology* / Q000378:metabolism; D012423:Rural Health; D012494:Sampling Studies; D013960:Thyroid Function Tests
D011193:Potassium Iodide; D007455:Iodine