Intelligence quotient is associated with epilepsy in children with intellectual disability in India

Introduction

Epilepsy is defined as recurrent, unpredictable, and typically unprovoked seizure activity.[1] The prevalence of epilepsy in the general population is estimated to be 40-70/1000 people;[2] people with intellectual disability (ID) have a higher rate of epilepsy diagnoses than the general population. ID was known as mental retardation earlier, and we have used these terms interchangeably in manuscript. Approximately 14-24% of the ID population is affected by epilepsy.[34] The prevalence of epilepsy increases with the severity of ID, which approaches 7% in people with mild to moderate ID, 67% in people with severe ID,[5] and 50-82% in people with profound ID.[67] Dodson[8] reported that children with epilepsy have an intelligence quotient (IQ) score that is 10 points lower than their healthy, age-matched peers.

Epilepsy can affect a person's education, career, general health, mental health, and marriage, among other things.[9] Epilepsy in children with ID affects a number of domains and functions.[1011] For example, epilepsy affects their health-related quality of life outcomes[12] and their ability to function normally.[13] Children with both epilepsy and intellectual disabilities experience psychiatric disorders in 50-59% of cases.[1415] Epilepsy does not only affect the individual but it also negatively affects an individual's family members. In a review article, Bowley and Kerr[16] reported that having ID along with epilepsy affects a person's physical morbidity, which in turn leads to increased mortality and a greater burden on their family.

The risk of death is five times higher in children with epilepsy compared with children without epilepsy.[17] This risk is even higher in children with ID that also have neurological disorders.[17] Because epilepsy is a known neurological disorder,[7] it follows that children who have low IQ scores and epilepsy have an even higher death risk. Given these correlations, a strong relationship seems to exist between epilepsy and low IQ,[18] but very few studies have investigated the nature of this relationship. If the relationship was linear within the ID population, one would potentially be able to predict how a person's IQ score relates to their likelihood of having or developing epilepsy.

Materials and Methods

Results

Table 1 categorizes variables characteristics and statistics. We found epilepsy highly associated with male gender than female (X² −7.399, P = 0.005) and not equally distributed with severity of ID (X² −57.21, P = 0.001). Epilepsy found strongly associated with the children those have family history of mental illness (X² −7.389, P = 0.007), mental retardation (X² −9.42, P = 0.003), and epilepsy (X² −53.2, P = 0.001). Except psychiatric disorders and Down's syndrome, epilepsy is found more among ID children those had cerebral palsy (X² −33.97, P = 0.001), and behavior disorders (X² −5.709, P = 0.01). The occurrence of epilepsy is not different in population groups (X² −0.742, P = 0.427), and among socioeconomic groups (X² −2.608, P = 0.456) [Table 1].

Table 1 The association of epilepsy with different variables: Gender, socioeconomic status, population type, severity of intellectual disability, family history of mental illness, mental retardation, epilepsy, and coexisting disorder. Values are given for X² statistics and their corresponding P values

Table 2 it expresses Spearman's rho statistics of epilepsy with the ordinal variables age and intelligence quotient. Epilepsy had inverse correlation with age (P = −0.683), and intelligence quotient (P = −0.605) among children with intellectual disability. Graphs demonstrate that prevalence of epilepsy decreases with the age [Figure 1] and intelligence quotient [Figure 2] of intellectual disability children.

Table 2 Spearman correlation rho (P) of prevalence of epilepsy with age and intelligence quotient in children with intellectual disability

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Figure 1

Graph showing prevalence of epilepsy with the age of intellectual disability children

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Figure 2

Graph showing prevalence of epilepsy with the intelligence quotient of intellectual disability children

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Discussion

Spearman's P demonstrates that lower IQ scores are correlated with epilepsy in children with ID. A case-control study conducted in North India demonstrated that children with generalized epilepsy have lower IQ scores than their controls with not epilepsy.[25] A linear decline in IQ is also seen among people who developed epilepsy.[26] Epilepsy also found more associated with male gender and that was consistent with our study. Epilepsy is equally distributed between two populations tribal versus nontribal. Children with ID those had family history of mental illness, mental retardation and epilepsy shown higher chances of having epilepsy.

It is already known that people with ID have higher rates of epilepsy.[57] Further inferring from findings, we can say that people with ID are on higher risk than non-ID and this risk of epilepsy goes further higher among ID as their IQ score lowers.

Studies have shown correlation of epilepsy with poor cognitive function.[2728] Thus, professionals should use extra caution to detect epilepsy as early as person with ID come in their contact so that person can receive early diagnosis and treatment in order to protect from diminishing their cognitive abilities further. ID person those do not have epilepsy also need regular attention by professionals in order to check for any symptom of it, so that immediate care can be offered.

Conclusion

Despite the limitations, this study adds knowledge to the existing scientific literature by describing that a person's likelihood of suffering from epilepsy increases as IQ scores drop in children with ID. Thus, we can say that children with low IQ have a higher chance of displaying epilepsy and, therefore, should be routinely tested for the condition.