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Iodine deficiency impairs intellectual and neuromotor development in apparently‐normal persons: A study of rural inhabitants of north‐central China
Author(s) -
Boyages Steven C.,
Maberly Glen F.,
Morris John,
Eastman Creswell J.,
Collins John K.,
Jupp James J.
Publication year - 1989
Publication title -
medical journal of australia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.904
H-Index - 131
eISSN - 1326-5377
pISSN - 0025-729X
DOI - 10.5694/j.1326-5377.1989.tb136760.x
Subject(s) - iodised salt , intelligence quotient , iodine deficiency , iodine , demography , medicine , quotient , rural area , china , pediatrics , gerontology , psychology , geography , psychiatry , chemistry , cognition , mathematics , organic chemistry , archaeology , pathology , sociology , pure mathematics
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 schoolchildren 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 < 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. (Med J Aust 1989; 150: 676‐682)