Introduction

Epilepsy is one of the common disorders encountered in the practice of neurology. Epilepsy is estimated to be present in ~1% of the Indian population, giving an estimated number of patients in excess of 13 million patients.1 The most common etiologies of epilepsy include the central nervous system (CNS) infections, tumors, neurotrauma, and genetic syndromes.2 A few types of epilepsy have been described in particular geographic regions, namely “hot water epilepsy” from South India.3 The pattern and presentation of the epilepsy are similar between the developed and developing countries. However, certain regional disparities exist between the urban and rural regions about the epidemiological determinants of the epilepsy.4 The epilepsy is often underdiagnosed and treated inadequately in the rural parts of India.

The epidemiological studies from India about the epilepsy are scarce and limited for many reasons.5 First, the diagnosis is often confused between the syncope and pseudoseizures. Second, the patients are completely normal in the interictal period leading to misdiagnosis. Third, the associated stigma leads to underreporting of the epilepsy, especially from the rural areas.6 Finally, the diagnosis and classification of epilepsy and seizures are not uniform among physicians leading to poor data compilation. A comprehensive epidemiological data are essential to identify the disease burden in the community and allocate the resources. A limited number of studies exist from India that have described the incidence rate of epilepsy in the community.7 8 9 However, these studies are limited by their sample size, distribution, and the duration of observation. Hence, we conducted this study to assess the incidence rate (IR) of epilepsy in a cohort of service personnel followed for a long duration.

Materials and Methods

Results

The study participants consist of 51,217 males (median age: 33 years, range: 17–54) followed up for a mean duration of 12.5 years. Our data gave a total 613,925 py duration of the follow-up period. Epilepsy was diagnosed in 291 patients, giving an incidence rate of 0.47 per 1000 py (95% confidence interval between 0.42 and 0.53). The mean age of the patients at the time of diagnosis of epilepsy was 27.9 ± 5.5 years. The mean duration of follow-up after the diagnosis was 8.3 ± 6.7 years. A total of 198 patients with epilepsy had comorbid ailments as shown in Fig. 1 The top four comorbid ailments observed in these patients include undifferentiated spondyloarthropathy, CNS disorders, alcohol dependence syndrome (ADS), and fractures as shown in Table 1. Our data do not give any information about the deceased individuals and the contribution of the epilepsy to the mortality.

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Fig. 1 Flow diagram of the study.

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Fig. 1 Flow diagram of the study.

Discussion

Our data showed an incidence rate of 0.47 per 1000 py of epilepsy in the service population observed for over two decades. Previous studies from India have shown that the incidence rate varied between 0.2 and 0.6 per 1000 population.11 Two studies from the rural parts of India have given an incidence rates of 0.47 and 0.49 per 1000 population.7 8Our data pertain to males only, whereas the other studies involve patients of both genders, precluding a meaningful comparison with our data. Sawhney et al have reported a higher incidence rate (6 per 1000) in the urban migrant population.12 The incidence rate derived from our data is in the expected lines with other studies and also eliminates the bias associated with the previously reported data from the urban area. Another study from the urban area has shown an incidence rate similar to that of our study, though with a smaller sample.9 In our data, the mean age of presentation of epilepsy is in the third decade. Previous reports suggest a bimodal distribution of age with the peaks in the first and sixth decade.13 However, our study sample includes patients beyond 18 years of age only, thereby limiting the comparison with other studies. Recent reviews have suggested an increasing prevalence in the second to fourth decade due to the demographic transition of the population.14 Previous reports suggest a slightly higher prevalence rates in the male gender.15 We are unable to comment on gender differences as our data do not include any females.

Another important finding of our study is the associated comorbid ailments in the patients with epilepsy. Undifferentiated spondyloarthropathy is the most common ailment seen in 68% of patients with epilepsy. This could have been contributed by the associated occult vitamin D deficiency (VDD) as explained below: First, VDD is very common in India and they present with osteomalacia and myalgia.16 Second, the use of antiepileptic drugs (AEDs) such as valproate and phenytoin results in the VDD, aggravating the symptoms.17 Third, vitamin D is not routinely supplemented in our patients using an AED. Finally, the food products and milk are not fortified with vitamin D in India, leading to significant VDD in the general population. ADS is the third common disorder seen in our patients with epilepsy. Our study population, being derived from the military service, has a higher prevalence of alcohol consumption in comparison to the general population.18 However, the EMR includes the data about the patients who fulfill the diagnostic criteria for ADS only and excludes the patients with binge drinking and other forms of alcohol consumption.

Neuroinfections, neurotrauma, and metabolic conditions are the common etiologies of the epilepsy from India.19 However, our data suggest idiopathic (32%) as the most common disorder followed by neuroinfections (14%), alcohol (14%), and psychiatric disorders (10%). The discrepancy in our database could be explained by the relatively young population, good socioeconomic status, and the possibility of exclusion of certain infections separately in the database. Neurocysticercosis (NCC) is a common cause of epilepsy, and in a typical case, the treating physician could have labeled the individual as only a case of epilepsy without giving a separate diagnosis of NCC.20 We have not perused the individual medical records of the patients, to identify the exact etiology and the type of the epilepsy. The strengths of our study include longer duration of observation and robust follow-up of a sizeable number of patients. The absence of data pertaining to the female sex and possible clerical errors in data entry leading to misdiagnosis of ICD codes are certain limitations of our study. Another limitation is the lack of information about the HCPs who are treated outside our organization resulting in low IR of the epilepsy. We have not observed the participants before their entry into the military service to rule out a preexisting epilepsy, thereby resulting in another limitation of our study.

Conclusion

Our report showed the incidence rates of epilepsy from a large service population of India. Our data are comparable with that of the other published reports on the epilepsy and help in the reliable estimation of the disease burden in the community.