Keywords
unprovoked seizures - epidemiological survey - age-adjusted incidence
Introduction
Prevalence studies are important to know about disease burden and incidence studies
are required to know the etiology and natural course of illnesses. At the global level,
it is estimated that approximately 70 million people suffer from epilepsy and prevalence
of epilepsy is estimated to be 5 to 9 per 1000 population.[1] Out of the 17 million disease-adjusted life years (DALYs) in global burden of epilepsy,
nearly 90% are from low- and middle-income countries. Southeast Asia contributing
for 3.2 million DALYs and more than half of total DALYs were accounted from India.[1] Within the Southeast Asia region, the prevalence of epilepsy varied from 2 to 10
per 1,000 population. There are approximately 22 epidemiological studies on epilepsy
from different parts of India, both from rural and urban areas.[1] The prevalence rate stands at around 5/1,000 population (at this rate, present estimate
of total population with epilepsy in this country is ~6.5 million).[1]
Incidence is the number of new epilepsy cases occurring during a given time interval,
usually in 1 year, in a specified population. Most incidence studies of epilepsy are
from developed countries with a rate of 40 to 70 per 100,000 populations.[2] In 1993, Bannerjee et al, reported the incidence of 44 per 100,000 of population
from Rochester through a 50-year follow-up period.[2] Such long follow-up of population is not possible in developing countries and in
India due to lack of structural health care system. There is an inherent complexity
and resource intensity involved in conducting such incidence studies, thus very few
incidence studies are available from India.
Studies from India have reported incidence rates varying from 27 to 60 per 100,000
population.[1] Saha et al reported an incidence of 42 per 100,000 population from a 5-year longitudinal
study in rural West Bengal which was similar to incidence rate of 49 per 100,000 population
reported by Mani et al from the 1-year Yelandur study in rural Karnataka.[3]
[4] From urban India, rates are quite variable from 27 to 60 in two different studies.[1] The main limitation to conduct an incidence study is poor health registry and case
reporting at the primary health care system and nonavailability of health-related
records. This type of study is more difficult in hills of Uttarakhand. Here, we conducted
this survey to study incidence of all new onset unprovoked epilepsy cases in rural
and semiurban areas of the Uttarakhand State. This study was conducted on large scale
population of people residing in hills of Himalayas with difficult terrain and all
new patients were subjected to investigation to find out possible etiology and sociodemographic
linkage of all seizure cases in selected population. Also this is aimed to find out
incidence of all new onset seizures cases in selected population.
Methods
Study Design and Setting
This was a community-based, longitudinal, observational study in two blocks of Dehradun
district in Uttarakhand state. The Chakrata and Doiwala blocks were randomly selected
by lottery. Chakrata block is least in terms of composite block index (CBI) in the
district of Dehradun and covered by hills. The Chakrata block is approximately 80
km away from Dehradun, the capital of Uttarakhand state. This is at approximately
3,000- to 7,000-feet height from sea level with very difficult areas to reach. There
are approximately 153 villages in 100 km2 area. This block is divided in nine nyay panchayat (NP). According to census 2001,
total number of households and population in Chakrata block were 6,445 and 49,097,
respectively. Doiwala block on the other hand is having five NP areas consists of
semiurban area of plains of Uttarakhand. Out of five, only 2 NP areas (16 villages
having population of about 58884 people) from Doiwala were randomly selected.
Sample Size
Total population of approximately 100,000 from two blocks had been selected for survey
(50,000 in each block). Keeping the average incidence of 40 to 50 per 100,000 in India,
there will be approximately 100 to 150 new cases in 3 years.
Survey
The survey team consists of field workers, supervisors, medical officer, and neurologist.
The annual door-to-door survey of the whole population was conducted every year in
months of April to June of 2015, 2016, and 2017. The survey was started simultaneously
in both the blocks by field workers and completed in 3 months. The quality of survey
was confirmed by field supervisors and medical officers. The data were collected on
the prevalidated National Institute of Mental Health and Neurosciences (NIMHANS) questionnaire
(used in the Yelandur study).[4] Based on the Yelandur model questionnaire, one family information Performa was developed
in local language ([Appendices A]
[B]). Each and every household were approached and head of family was interviewed for
family structure, demographic details, and seizure-related information. Children below
5 years had seizure with fever (question 7) and cases having only one positive response
to question 2a were excluded from analysis.
Case definition:
-
Old seizure case: seizure case with onset of disease before April 30, 2014.
-
New onset seizure case: case of seizure having onset after May 1, 2014.
After annual door-to-door survey, additional 3 monthly visits to the study population
was done by field supervisor and medical officer of our team to check the 10% of positive
and negative responders, to complete the information of missing data, to collect the
information of locked houses, and to find any new onset seizure case in community.
Those household having new onset seizure case(s) were approached by our field supervisor
and medical officer to record detail information about age of onset of seizure, type
of seizure, frequency of seizure episodes, family history of seizure, reports of investigations
done for seizures, and treatment taken with response to treatment. If no investigation
done in new onset cases, then they were subjected to magnetic resonance imaging (MRI)
and electroencephalography (EEG). Analysis of data was done at the end of 3 years.
New onset seizure cases having obvious provoking factors like seizures during hospitalization
due to any illness other than seizure disorder, seizure with febrile illness, headache,
and vomiting, seizure within 7 days due to acute central nervous system (CNS) insult-like
head injury, and seizures in a person with substance abuse were excluded from analysis.
Cases with single-seizure episode were included but patients with new onset status
epilepticus were not included.
Classification of seizures and etiology was based on International League Against
Epilepsy (ILAE) classification system for epidemiological studies in 1993.[6] Based on the 1993 ILAE classification, seizures were of three types (generalized,
partial, and unclassified) and etiologies were classified (on the basis of clinical,
EEG, and radiological findings) into acute symptomatic, remote symptomatic, idiopathic,
and unknown. Other operational definitions were same as defined according to ILAE
commission report 1997.[7]
Operational Definitions
Epilepsy: two or more unprovoked seizures or seizure episode. An unprovoked seizure
is one without an acute underlying cause.
Single-seizure episode: isolated or multiple seizures episode within 24 hours.
Status epilepticus: single or multiple seizures without regaining consciousness for
more than 30 minutes.
Active epilepsy: a person with seizure in past 5 years regardless of treatment status.
Febrile seizure: seizure in a child between 6 months and 5 years of age with fever
(not due CNS infection).
Definition of Putative Etiology
Symptomatic seizures: symptomatic seizures or epilepsies are considered the consequence
of a known or suspected cerebral disease. Acute symptomatic seizures defined as seizure
occurring in close temporal association with an acute systemic, metabolic, or toxic
insult or in association with an acute CNS insult. Such seizures are often isolated
epileptic events associated with acute conditions, but may also be recurrent seizures
or even status epilepticus when the acute conditions recurs.
Unprovoked seizures: seizures may occur in relation to well demonstrated antecedent
conditions, substantially increasing the risk for epileptic seizures.
Unprovoked seizures of unknown etiology: cases of unprovoked seizures for which no
clear antecedent etiology can be detected.
Idiopathic epilepsies: used herein as defined by the ILAE and must be reserved for
certain partial or generalized epileptic syndromes with particular clinical characteristics
and with specific EEG findings and should not be used to refer to epilepsy or seizures
without obvious cause.
Cryptogenic epilepsies: used to include partial or generalized unprovoked seizures
in which no factor associated with increased risk of seizures has been identified.
Non epileptic event: clinical manifestations presumed to be unrelated to an abnormal
and excessive discharge of a set of neurons of the brain, including disturbances in
brain function and pseudo seizures.
Seizure Type Classification
Generalized seizures: a seizure is considered generalized when clinical symptomatology
provides no indication of an anatomic localization and no clinical evidence of focal
onset.
Partial seizure: a seizure should be classified as partial onset when there is evidence
of a clinical partial onset, regardless of whether the seizure is secondarily generalized.
Multiple seizure: when both generalized and partial seizures occur.
Unclassified seizure: used when it is impossible to classify seizures, owing to lack
of adequate information.
Measurable Epidemiological Index
Period prevalence: the proportion of patients with epilepsy in a given population
during a defined time interval.
Incidence rate: the ratio of new cases to population at risk, usually expressed as
cases per 100,000 of population per year.
Quality Control
Field workers and supervisors were trained at the Department of Community Medicine,
Himalayan Institute of Medical Sciences in Dehradun for questionnaire filling, seizure-related
history, true seizures, and nonepileptic seizures for the field work, and to know
about provoked seizures like febrile convulsions and alcohol-related seizures or other
metabolic toxic conditions. Hot water epilepsy and other reflex epilepsy are not found
in this area. These workers were also the part of our team while we performed prevalence
study in year 2008 with the same questionnaire, therefore validation and sensitivity/specificity
assessment was not conducted.[8]
Statistical Analysis for Epidemiological Parameters Measured in Current Study
Prevalence: included all surviving cases of seizures before May 1, 2014. Prevalence
was expressed as numbers per 100,000 of population.
Annual incidence rate (AIR): indicates new cases of epilepsy per 100,000 of population
per year. The average AIR (AAIR) indicates average of all 3 years for new cases per
100,000 of population per year.
Age standardization: The age standardization of prevalence and incidence rates was
done with World Standard Population (WSP) according to Ahmad et al.[9] The 95% confidence interval (CI) of incidence and prevalence were calculated assuming
a Poisson’s distribution of the observed cases.
SPSS 20 version was used for frequency analysis and regression analysis (univariate
and multivariate analyses). All seizure cases cluster was analyzed for various sociodemographic
parameters and labeled as significant if p < 0.05.
Result
A total of 7,649 households (56,399 population) in nine NP areas of Chakrata block
and 10,874 households (47,211 population) in Doiwala block were surveyed. Among total
population of 103,610 (54,158 men and 49,452 women), living in 26,172 households were
screened. Distribution of age, gender, and sociodemographic variables in the selected
population is given in [Table 1]. The [Table 1] also shows significance of various sociodemographic parameters in relation with
seizure cluster. Age, gender, caste, and poverty level were significant factors linked
with seizure cluster on univariate analysis. Among dietary and personal hygiene-related
factors, nonvegetarian diet, mud house, nonavailability of separate kitchen and/or
toilet, and source of drinking water were found significantly associated with seizure
patients. Education, occupation, and overcrowding were not found significant in association
with seizures cases on univariate analysis. On multivariate analysis ([Table 2]) on all seizures patients, age, nonvegetarian diet, and separate kitchen were significantly
associated with seizure patients.
Table 1
Profile of whole population according to sociodemographic parameters
|
Variable
|
Frequency
n (%)
|
Association of demographic variable with seizure on univariate analysis (p-value)
|
|
Abbreviations: APL, above poverty line; BPL, below poverty line; OBC, other backward
class.
|
|
Total population surveyed
|
103,610 (100)
|
|
|
Total seizure cases over 3 years
No seizure population
|
833 (0.8)
102,777 (99.2)
|
|
|
Gender
1. Male
2. Female
|
54,158 (52.3)
49,452 (47.7)
|
0.005(significant)
|
|
Age group (y)
1. Early childhood (0–4)
2. Late childhood (5–14)
3. Adolescent (15–19)
4. Adults (20–59)
5. Elderly (>60)
|
8,141 (7.9)
22,325 (21.5)
10,775 (10.4)
53,785 (51.9)
8,584 (8.3)
|
0.000 (significant)
|
|
Caste
1. General
2. OBC
3. Schedule cast
4. Schedule tribe
|
45,430 (43.8)
2,555 (2.5)
19,475 (18.8)
36,150 (34.9)
|
0.001 (significant)
|
|
Poverty level
1. APL
2. BPL
|
73,970 (71.4)
29,640 (28.6)
|
0.000 (significant)
|
|
Education
1. Post graduate
2. Graduate
3. Intermediate
4. High school
5. Primary
6. Illiterate
|
1,728 (1.7)
5,465 (5.3)
12,931 (12.5)
7,981 (7.7)
46,997 (45.4)
28,508 (27.5)
|
0.075 (not significant)
|
|
Occupation of family head
1. Business (own work)
2. Farming
3. Service (with retired)
4. Labor class (daily wedges)
|
12,807 (12.4)
72,858 (70.3)
11,878 (11.5)
6,067 (5.9)
|
0.808 (not significant)
|
|
Major diet pattern
1. Vegetarian
2. Nonvegetarian
|
30,029 (29)
73,581 (71)
|
0.000 (significant)
|
|
House type
1. Kuccha (mud house)
2. Pukka (bricked)
3. Mixed
|
6,934 (6.7)
90,914 (87.7)
5,762 (5.6)
|
0.036 (significant)
|
|
Separate kitchen
1. No
2. Yes
|
8,504 (8.2)
95,106 (91.8)
|
0.000 (significant)
|
|
Separate toilet
1. No
2. Yes
|
16,801 (16.2)
86,809 (83.8)
|
0.000 (significant)
|
|
Source of water
1. Community water source/hand pump
2. Owned tap
|
15,631 (15.1)
87,979 (84.9)
|
0.000 (significant)
|
Table 2
Multivariate analysis of all seizure patients with sociodemographic factors
|
Parameter
|
Significance
|
Odd ratio
|
95% CI
|
|
Lower
|
Upper
|
|
Abbreviations: APL, above poverty line; BPL, below poverty line; CI, confidence interval;
OBC, other backward class; SC, schedule cast; ST, schedule tribe.
|
|
Age group
|
0.000
|
|
|
|
|
Late childhood
|
0.000
|
0.475
|
0.313
|
0.722
|
|
Adolescent
|
0.000
|
0.262
|
0.172
|
0.401
|
|
Adult
|
0.000
|
0.334
|
0.225
|
0.497
|
|
elderly
|
0.000
|
0.424
|
0.268
|
0.672
|
|
Caste
|
0.518
|
|
|
|
|
OBC
|
0.715
|
1.121
|
0.931
|
1.349
|
|
SC
|
0.993
|
1.033
|
0.672
|
1.586
|
|
ST
|
0.227
|
1.122
|
0.925
|
1.362
|
|
APL/BPL
|
0.024
|
1.208
|
1.025
|
1.424
|
|
Vegetarian/nonvegetarian
|
0.001
|
1.392
|
1.155
|
1.678
|
|
Type of house
|
0.209
|
|
|
|
|
Mud house
|
0.154
|
1.24
|
0.922
|
1.666
|
|
Mixed house
|
0.183
|
1.237
|
0.904
|
1.693
|
|
Separate kitchen
|
0.012
|
1.37
|
1.071
|
1.753
|
|
Separate toilet facility
|
0.75
|
1.046
|
0.794
|
1.378
|
|
Main source of drinking water
|
0.469
|
1.103
|
0.846
|
1.437
|
After first survey, a total of 783 had positive response for seizure with 733 old
cases and 50 new onset cases among 103,610 people. Additional four old cases were
found in 10% of negative responders, so 40 cases added to a total of 773 cases (746.06
per 100,000). A total of 83 children below 5 years had febrile convulsion and they
were excluded from analysis. Additional 22 cases excluded, as they responded for only
one episode of unconsciousness and all other responses were negative (possible nonepileptic
event). Thus, a total of 668 old cases of all afebrile seizures (active cases) were
finally analyzed for the crude prevalence rate (with 95% CI) of 648.67 (537.26–760.08)
per 100,000 of population. The crude prevalence among men was 757.93 (95% CI: 639.95–875.91)
and in women was 577.85 (95% CI: 391.28–764.42). When age standardization to WSP done,
overall prevalence was 623.63 (95% CI: 510.03–737.23) per 100,000 population; mean
age-adjusted prevalence rate (AAPR) was 762.03 (95% CI: 642.53–881.53) and among women
was 472.01 (95% CI: 323.71–620.31) per 100,000 population ([Table 3]). Linear graph in [Fig. 1] showed that AAPR is having bimodal pattern with initial peak at 20 to 25 years and
second peak around 70 years.
Table 3
Age- and gender-specific rates of all seizure cases
|
Men
|
Women
|
Overall
|
|
Abbreviations: ASR, age standardize rate; AAIR, age-adjusted incidence rate; CI, confidence
interval; POP, population; PR, prevalence rate.
|
|
Age (y)
|
POP
|
PR
|
AAIR
|
POP
|
PR
|
AAIR
|
POP
|
PR
|
AAIR
|
|
0–4
|
4,288
|
233.2
|
62.2
|
3,853
|
181.68
|
25.95
|
8,141
|
208.82
|
45.04
|
|
5–9
|
5,655
|
477.45
|
47.1
|
4,978
|
361.59
|
13.4
|
10,633
|
423.21
|
31.34
|
|
10–14
|
6,100
|
688.52
|
76.5
|
5,592
|
608.01
|
59.6
|
11,692
|
650.01
|
68.42
|
|
15–19
|
5,696
|
842.7
|
46.8
|
5,079
|
1,102.58
|
72.2
|
10,775
|
965.2
|
58.77
|
|
20–24
|
4,710
|
976.65
|
77.8
|
4,412
|
1,087.94
|
52.9
|
9,122
|
1,030.48
|
65.77
|
|
25–29
|
4,619
|
844.34
|
57.7
|
4,613
|
845.44
|
43.4
|
9,232
|
844.89
|
50.54
|
|
30–34
|
4,230
|
898.35
|
55.2
|
3,826
|
731.83
|
43.56
|
8,056
|
819.27
|
49.65
|
|
35–39
|
3,915
|
817.37
|
42.6
|
3,974
|
427.78
|
50.3
|
7,889
|
621.12
|
46.47
|
|
40–44
|
3,536
|
791.86
|
94.3
|
2,864
|
558.66
|
34.9
|
6,400
|
687.5
|
67.7
|
|
45–49
|
2,826
|
1,026.19
|
47.2
|
2,461
|
365.7
|
40.6
|
5,287
|
718.74
|
44.1
|
|
50–54
|
2,120
|
801.9
|
31.4
|
1,960
|
663.27
|
51.02
|
4,080
|
735.29
|
40.85
|
|
55–59
|
1,870
|
748.66
|
53.5
|
1,849
|
432.67
|
54.08
|
3,719
|
591.56
|
53.78
|
|
60–64
|
1,562
|
704.23
|
106.7
|
1,617
|
494.74
|
41.22
|
3,179
|
597.67
|
73.4
|
|
65–69
|
1,341
|
1,267.71
|
24.86
|
1,143
|
349.96
|
58.3
|
2,484
|
845.41
|
40.26
|
|
70–74
|
863
|
811.12
|
38.6
|
640
|
625
|
104.1
|
1,503
|
731.87
|
66.53
|
|
75–79
|
425
|
705.88
|
78.4
|
305
|
0
|
0
|
730
|
410.96
|
45.66
|
|
80+
|
402
|
248.76
|
82.9
|
286
|
0
|
0
|
688
|
145.35
|
48.45
|
|
TOTAL
|
54,158
|
757.93
|
60.2
|
49,452
|
519.81
|
43.85
|
103,610
|
648.67
|
52.74
|
|
95% CI
|
|
639.95–875.91
|
49.78–70.66
|
|
373.82–665.8
|
32.12–55.58
|
|
537.26–760.08
|
47.21–58.27
|
|
ASR
|
|
762.03
|
59.2
|
|
472.01
|
43.53
|
|
623.63
|
51.63
|
|
95% CI
|
|
642.53–881.53
|
48.78–69.64
|
|
323.71–620.31
|
32.11–54.95
|
|
510.03–737.23
|
46.69–56.57
|
Fig. 1 Age-specific pattern of prevalence of epilepsy. PR, prevalence rate.
After 3 years, a total of 201 cases of new onset seizures were recorded in selected
community ([Table 4]). Total 36 cases having obvious provocation factor (febrile illness in 22, substance
abuse in 6, acute head injury in 5, and, during hospital stay, 3 patients for other
illness) were excluded. Therefore total 165 cases (mean = 55 cases per year) were
found without any obvious provoking factors. [Table 5] shows the etiological distribution of all new onset seizures cases without provoking
factor in both the blocks under surveillance. Overall crude incidence rate for all
new onset seizures cases was 52.74 (95% CI: 47.21–58.27) per 100,000 population. Among
men, crude incidence rate was 60.2 (95% CI: 49.78–70.66) and in women, it was 43.85
(95% CI: 32.12–55.58) per 100,000 population. Overall age-adjusted IR (AAIR) for all
new onset seizures was 51.63 (95% CI: 46.69–56.57), among men it was 59.2 (95% CI:
48.70–69.64), and among women AAIR was 43.53 (95% CI: 32.11–54.95) per 100,000 population
([Table 3]). [Fig. 2] shows bimodal peak of annual incidence rate at 20 to 39 years and more than 60 years
age group.
Table 4
The number of population and household selected for survey
|
Block
|
Panchayat area
|
House hold
|
Population
|
All seizure cases
Onset before 2014
|
New onset seizure cases (2014–15)
|
New onset seizure cases (2015–16)
|
New onset seizure cases (2016–17)
|
|
Chakrata block
|
9 areas
|
7,649
|
56,399
Male = 28,959
Female = 27,440
|
422
|
26
|
28
|
32
|
|
Doiwala block
|
8 areas
|
10,874
|
47,211
Male = 25,199
Female = 22,012
|
246
|
24
|
25
|
30
|
|
Grand total
|
17 areas
|
18,523
|
103,610
Male = 54,158
Female = 49,452
|
668
|
50
|
53
|
62
|
Table 5
Etiology and type of seizure among new onset cases
|
Etiology
|
Doiwala block (n = 86)
|
Chakrata block (n = 79)
|
Average annual Incidence rates according to etiology per 100,000 population
|
|
Acute symptomatic (granuloma)
Remote symptomatic
Primary/idiopathic
Unknown etiology
|
21 (27.8%)
10 (12.7%)
4 (5%)
44 (54.5%)
|
25 (28.8%)
11 (12.8%)
6 (7%)
44 (51.2%)
|
14. 79
.76
3.21
28.31
|
|
Type of seizure:
Generalized
Focal
Unclassified
|
38
24
24
|
21
24
34
|
59 (35.8%)
48 (29%)
58 (35.2%)
|
Fig. 2 Pattern of age-specific annual incidence rate (per 100,000) population.
After investigations done in all new onset seizure cases, 46 cases (27.9%) were having
brain granuloma/acute illness as a cause of seizure. Annual incidence rate of acute
symptomatic seizures (with intracranial granuloma/acute illness) was, 14.79 per 100,000
of people. Therefore, the annual incidence rate of all unprovoked seizures or epilepsy
(after excluding acute symptomatic seizures) was 38.28 cases per 100,000 of population
(included remote symptomatic, primary generalized and unclassified epilepsy). [Table 5] also showed the seizure type among all new onset cases and suggested nearly equal
distribution of generalized, partial, and unclassified seizures.
Discussion
After the 2010 study that was conducted in East India,[10] this is another longitudinal follow-up study over 3 years conducted in the Northern
part of India. This study was done with standard way of definitions, age standardization
according to WSP, and door-to-door survey. Over 100,000 of population were followed
to find new onset seizures in the community and their etiological profile. This study
was in continuation of our pilot study done in same geographical area on 14,000 of
population to find out crude prevalence rate.[8] In our study, we did not record data on mortality of patients suffering from seizures,
so could not analyze standard mortality rates (SMRs) among persons with epilepsy.
According to a review done by Banerjee et al,[2] a total of 48 prevalence studies for epilepsy cases were conducted globally among
which 29 studies had used door-to-door method of community-based survey. AAPR of epilepsy
were 500 to 710 per 100,000 people in North America, 370 to 2,200 per 100,000 in Central
and South America, 270 to 700 per 100,000 in Europe, and highest was in Nigeria with
4,400 cases per 100,000 population.[2] In another review by Amudhan et al in 2015, total 23 studies from rural and 22 from
urban India were mentioned that have analyzed the prevalence rates in different Indian
areas.[1] Both crude and age-adjusted prevalence of epilepsy in all ages were ranging from
lowest prevalence rate of 130 cases per 100,000 from Baroda and Pondicherry and highest
prevalence rate of 1,004 cases per 100,000 population from West Bengal and Karnataka.[1] AAPR was 572.80 per 100,000 in a study by Banerjee et al in 2010 which was similar
to Sridharan et al in 1999.[10]
[11] In our study, we found little higher AAPR of active unprovoked seizures 623.63 per
100,000 population. The higher prevalence of epilepsy is due to higher rates on neurocysticercosis
leading to permanent epileptogenic focus as mentioned in earlier studies.[12] Most of the studies form developing countries showed a stable pattern of AAPR rate
of epilepsy up to forth decade then fall of the rates fifth decade onward, but our
study showed bimodal pattern with first peak in second to third decade and other peak
at 6th – 7th decade.[10] Most of the studies on age-specific prevalence showed peak during early childhood
or adolescence,[2] our study also showed peak at adolescent age group (1.2% in adolescents vs. 0.8%
overall). Gender-specific prevalence in most studies and our study showed higher prevalence
in males (7.57 vs. 5.19).
Regarding AAIR of epilepsy, a total of 15 studies were recorded with definition of
recurrent unprovoked seizures.[2] In North America, AAIR ranged from 16 to 51 per 100,000, 111 per 100,000 in South
America, 26 to 47 per 100,000 from Europe, and 43 to 51 per 100,000 from African region.[2] Four Indian studies have analyzed the incidence rates of epilepsy till 2015 review.[1] Two studies with 5-year longitudinal follow-up of selected population to study AAIR,
found incidence rate of 42 per 100,000 (20,966 population) from West Bengal in 2008
and 27 per 100,000 (52,377 population) again from West Bengal in 2010.[3]
[9] One study by Amudhan et al from Chandigarh found AAIR of 60 per 100,000 of population
in 4-year follow-up.[1] The first incidence study in India was conducted by Mani, et al from Karnataka,
and found AAIR of 49.3 per 100,000 of population in 1-year follow-up.[5] Overall, AAIR of all new onset seizure cases (after excluding seizures with obvious
provoking factors) in our study was 51.63 per 100,000 of population. We were following
all new onset seizures cases in community area at every three months interval with
clinical survey and investigations available, and found AAIR of 14.79 per 100,000
for acute symptomatic seizures either due to cerebral cysticercosis/tuberculoma (granuloma
related). Finally, AAIR of epilepsy (unprovoked seizures) in our study was 38.28 cases
per 100,000 of population after exclusion of acute symptomatic seizures.
Methodological issues in door-to-door survey of epilepsy are case ascertainment, determination
of etiology, not missing the actual cases, and overdiagnosis of nonepileptic cases.[2] In current study, case ascertainment and case definition was not only dependent
on door-to-door survey but information was gathered by multiple sources as suggested
earlier.[2] We took information from Accredited social health activists (ASHA) workers, head
of panchayat area, head of family, and medical record checkup. Along with this, we
had established community-based epilepsy clinic there for treatment of epilepsy, so
there was good clinical evaluation done for confirmation of case and etiology. Second
methodological challenge we faced that it was easy to recognize various provoking
factors of seizures like febrile seizure, alcohol-related seizure, and acute CNS injury-related
seizures, but case of acute symptomatic seizures due to granuloma were difficult to
recognize on clinical interview alone. For diagnosis of acute symptomatic seizures
due to granuloma, we needed imaging, so that these cases always get registration in
door-to-door survey.[10] The wide variation of prevalence and incidence rates of epilepsy in different national
and international studies depends on the methods used, as well as on the population
selected as study from endemic area for neurocysticercosis would show high rates.[11]
After statistical analysis diet pattern and hygiene-related social factors were found
significant as nonvegetarian diet, nonavailability of separate toilet/kitchen and
community source of water were having high prevalence of seizures. Since the selected
population is in high-endemic zone for neurocysticercosis, many of these patients
can become chronic epilepsy patient in long-term follow-up.[11] Open field defecation and poor water sanitation can increase prevalence of neurocysticercosis
and overall chronic epilepsy due to calcified granuloma.[12] We propose that improvement with close toilet facility and better water sanitation
can reduce overall disease burden in long-term follow-up.
Strength and Limitation
Strength of the current study is the large population with evaluation of all new onset
seizure cases by neurologist to recognize the correct and etiological evaluation of
all new cases. Limitation was that we have only 3 years to follow-up and longer duration
would have been better. Other weak points of current study were not accounting for
single seizure, not included data on death of seizure patients, and no account for
refractory epilepsy.
Conclusion
After longitudinal follow-up for 3 years among 103,610 population in two blocks of
Uttarakhand state, we found AAPR of all seizures cases to the tune of 623.63 cases
per 100,000 of population. Overall annual incidence rate of all seizure cases was
51.63 per 100,000 population. AAIR rate of epilepsy was 38.28 per 100,000 population
and annual incidence of acute symptomatic seizures was 14.79 per 100,000 of population.
Diet patterns and hygiene-related factors were significantly associated with seizure
cases in selected community. We propose that open field defecation can be high risk
for increasing epilepsy burden in our community and close toilets with water sanitation
will be helpful to reduce disease burden.
