In the present study, the distribution of children in the first group according to their residential places is as follows: rural area of 14%, popular area of 74.4%, and non-popular area of 11.6%. Rural areas and popular areas had higher ID prevalence rate than urban areas, which matches with study by Lai et al. (2011), which revealed that rural areas had higher incidence than urban areas. On the other hand, it goes against the study applied on Indian children by Lakhan et al. (2015) showing that the intellectual disability prevalence rate in children is slightly higher in urban than rural areas. So it needs further study.
In the present study, the distribution of the group of lower IQ is higher percentage of birth order more than 2; according to the results of the previous study, IQ scores were negatively associated with both birth order and social order (Kristensen and Bjerkedal 2007).
In the present study, there is significant relationship between IQ and gross motor development, which goes with a study by Rintala and Loovis (2013) that showed that intellectually disabled children have low gross motor skills on the other hand it is against the previous study revealed that there is no significant association between cognition aspects and gross motor development (Capute et al. 1985). In the present study, there is significant association between IQ and hyperactivity as it regarded to be more prevalent among the higher IQ children, on the other side a previous study revealed that there is a weak association between IQ and hyperactivity (Jespsen et al 2008) which needs further study.
In the present study, there is significant difference between the two groups (lower and higher IQ); the total leukocytic count was higher value for low IQ children group, which goes with a study by Strouse et al. (2006) which revealed that elevated white blood cells are associated with lower IQ.
In the present study, there is no significant difference in the Hb level between the two groups of lower and higher IQ, on the other hand a previous study showed that low hemoglobin level has negative effect on the children cognition (Ai et al. 2012) that needs further study.
In the present study showed no significant difference in platelets count and volume between two groups of children (of higher and lower IQ); in a previous study revealed that there is no significant difference in platelets count and volume between normal and autistic and schizophrenic children (Geller et al. 1988).
In the present study, the water intake is inversely proportional to IQ level; a study revealed that the concentration of fluoride in drinking water has direct effect on the IQ of children (Razdan et al. 2017).
In the present study, the caloric intake is inversely proportional to IQ level; in the previous study, malnutrition has direct effect on child development (Ampaabeng and Tan 2013).
In the present study, the carbohydrate intake is inversely proportional to IQ level and this correlation close to be significant. Previous study applied on Tehrani children aged 6–7 years gave evidence, indicating an inverse relationship between refined carbohydrate consumption and non-verbal intelligence (Abargouei et al. 2012).
In the present study, there is a significant correlation between protein intake and IQ level of children, as the protein intake is inversely proportional to IQ. In the previous study revealed that increased protein intake in the first weeks of life increases the mental development of newborn (Stephens et al. 2009).
In the present study, the fat intake is inversely proportional to IQ level with significant difference between the two groups of lower and higher IQ, which goes with a study by Theodore et al. (2009) that applied on European children of age 5–7 years old revealed that eating margarine at least daily was associated with significantly lower IQ scores.
In the present study, there is significant correlation between fiber intake and IQ level, on the other hand the fiber intake is inversely proportional to IQ level of children which goes against recent nutritional researches have found that dietary fiber was directly related with cognitive development among prepubertal children. Fiber intake may have a significant effect on cognitive and brain health through immunomodulation and/or the gut–microbiota–brain system (Khan et al. 2015) which needs further study.
In the present study, there was significant correlation between sodium intakes with IQ, the sodium intake is inversely proportional to IQ level of children. In the previous study showed no relation between sodium intake and IQ level of children (Ghazi et al. 2013).
In the present study, there is significant correlation between IQ and potassium intake, in which it is inversely proportional to IQ level of children, this results against a study by Ghazi et al. (2013) revealed that no relationship between IQ and potassium intake, which needs further study.
In the present study, calcium and iron showed no significant correlation with IQ of children which goes with the previous study by Ghazi et al. (2013) in the present study zinc and vitaminB2 intake showed significant correlation with IQ of children which goes against a study by Ghazi et al. (2013) that showed no correlation between zinc and vitamin B2intake and children IQ level, that needs further study.