Fluoride Action Network


Background: Exposure to high fluoride levels in drinking water can lead to a number of adverse effects in children, including cognitive dysfunction. Despite being endemic for fluorosis, studies on its effect on the cognitive function of children are lacking in Kerala.

Aims: The aim of this study was to compare the cognitive function of school children with fluorosis with that of normal children and to correlate between the severity of dental fluorosis and cognitive function.

Settings and design: Cross-sectional study, conducted in collaboration with the National Fluorosis Control Programme, among school children in Alappuzha district, Kerala.

Methods: Children aged 8-10 years, studying in 2 lower primary schools in Alappuzha district with confirmed fluorosis were selected, and compared with healthy age- and sex-matched children from the same school. Raven’s Standard Progressive Matrices and MISIC digit span subtest were used to assess the cognitive function.

Statistical analysis: Continuous variables were assessed by independent samples t test and categorical variables by Chi-square test. The relationship between severity of dental fluorosis and grade of cognitive impairment was assessed using Spearman’s correlation.

Results: There were 60 children each in fluorosis and control groups. The mean age of the children was 8.95 ± 0.50. Only 15% of the children with fluorosis scored Grade I and II Raven’s SPM grades (Intellectually superior/above the average) versus 30% in the control group. None of the children without fluorosis scored Grade V (intellectually impaired) category versus 20% in the fluorosis group. The mean digit span was significantly higher in the control group. A strong positive correlation between severity of dental fluorosis and Raven’s SPM grades was found (Spearman’s correlation coefficient = 0.740).

Conclusions: Fluorosis is associated with impaired cognition in children. There is a positive correlation between severity of dental fluorosis and the grade of cognitive impairment.

Keywords: Cognitive function; MISIC digit span test; Raven’s SPM; dental fluorosis.



… To the best of our knowledge, this is the first study conducted in Kerala to study the association between fluorosis and cognitive function. The children enrolled in the fluorosis group were those with dental fluorosis, confirmed by urine fluoride testing, further their drinking water was also tested for high fluoride level which establishes exposure to excess fluoride. The neuropsychometric tests performed to assess the cognitive function were Raven’s SPM and MISIC digit span subtest which are relatively culture-independent and reflect diverse functional domains, including memory, attention and tracking, visuospatial organization and reasoning, motor, and dexterity skills.


This is only a comparative study; hence causality between fluorosis and cognitive dysfunction cannot be established. Cognitive function of an individual is known to be influenced by complex interactions between various genetic and socio-economical factors. Though we have tried our best to select a homogenous sample with that regard, complete exclusion of such factors is not possible. Other heavy metals such as arsenic and lead were not analyzed in our study, which could very well contribute to cognitive dysfunction. Further research is needed to assess their individual impact as well as interaction with fluoride.


This study establishes a significant relationship between the presence of fluorosis and impaired cognition in children. The severity of dental fluorosis has a positive correlation with the grade of cognitive dysfunction. Fluorosis being a preventable cause of cognitive impairment in children, appropriate measures must be employed to reduce the level of fluoride in drinking water to the optimal level, in endemic areas.

These could include installation of more number of reverse osmosis (RO) plants at the community level with the help of local governing bodies and also providing RO water purifiers at subsidized rates to homes. It would also be beneficial to screen children with dental fluorosis for cognitive impairment, so as to initiate cognitive rehabilitation therapy.


• Response to study from Panda PK, Moirangthem V, Sharawat IK at http://fluoridealert.org/wp-content/uploads/panda-response-to-prabhakar-study.2021.pdf

•• Authors’ response to Panda et al. at http://fluoridealert.org/wp-content/uploads/prabhakar-reply-2021.pdf