Iodine deficiency impairs intellectual and neuromotor development in apparently-normal persons. A study of rural inhabitants of north-central China

Med J Aust. 1989 Jun 19;150(12):676-82.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Audiometry
  • Child
  • China
  • Cognition Disorders / epidemiology
  • Cognition Disorders / etiology*
  • Cognition Disorders / metabolism
  • Cohort Studies
  • Congenital Hypothyroidism / epidemiology
  • Congenital Hypothyroidism / etiology
  • Female
  • Goiter / epidemiology
  • Goiter / etiology
  • Hearing Loss, Sensorineural / diagnosis
  • Hearing Loss, Sensorineural / etiology
  • Humans
  • Intelligence / drug effects*
  • Intelligence Tests
  • Iodine / deficiency*
  • Iodine / therapeutic use
  • Iodine / urine
  • Male
  • Potassium Iodide / therapeutic use
  • Psychomotor Disorders / epidemiology
  • Psychomotor Disorders / etiology*
  • Psychomotor Disorders / metabolism
  • Rural Health
  • Sampling Studies
  • Thyroid Function Tests


  • Potassium Iodide
  • Iodine