Prevalence of autism spectrum disorders among children (1-10 years of age) - findings of a mid-term report from Northwest India.

BACKGROUND: India is the second most populous country of the world. A large portion of the population of this country is below 20 years of age but still there is a paucity of information about the prevalence and incidence of many developmental disorders. This study was planned to estimate the prevalence of autism spectrum disorders (ASDs) in the selected areas (tribal, rural, and urban) of a northern state of India, Himachal Pradesh.
METHODS: A cross-sectional two-phase study was conducted covering all the children in the range of 1-10 years of age. Phase one included screening of all the children in the age group of 1-10 years, with the help of an indigenous assessment tool for autism. The sociodemographic profile of the participants was also recorded during phase one. Phase two involved the clinical evaluation of individuals who were suspected of autism on screening.
RESULTS: The results show a prevalence rate of 0.9/1000. The highest prevalence rate was observed in the rural area.
CONCLUSIONS: Socioeconomic status (SES) may be one of the fundamental indicators for ASDs in India.

Introduction

Autism spectrum disorder (ASD) is a spectrum that includes individuals with profound mental retardation and little or no speech or communication compared to more verbal, functionally able children.[1] It is a neurodevelopmental syndrome that is defined by deficits in social reciprocity and communication, and by unusual restricted, repetitive behaviors.[2] It manifests in the first few years of life.[3] There is evidence of links between ASD and other developmental disorders as well as association with specific medical conditions. ASD continues to be an important public health concern.[4]

Studies worldwide are reporting that more children than ever before are being diagnosed with autism.[56789] Over the past decade or so, studies across the world have estimated an increase between 50% to over 2,000% in cases of autism.[6] However, there are no specific community-linked studies on the prevalence or incidence of autism or ASD in India[10] and hence the present study.

Methods

Ethics

The study protocol was approved by the Institutional Ethics Committee and written, informed consent was obtained from parents of the children. Assent was obtained from children over the age of 7 years.

Study site

The study was carried out to estimate the prevalence of ASDs in a north western state of India, Himachal Pradesh. Himachal Pradesh this state has a predominant mountainous terrain with altitude ranging from 350 m to 7000 m above the mean sea level and spread between the longitudes and latitudes of 75°47"-79°04" (East) and 30°22"-33°12" (North), respectively. The sample population for this study was selected from three distinct geographical areas of this state, namely, a tribal area, a rural area, and an urban area. For selecting these geographical areas, the entire geography of the state was mapped according to the notified description for each area and clustered as tribal cluster, rural cluster, and urban cluster. From each cluster, census blocks (for sample population) were selected by a simple random sampling technique.

Details of selected areas

Bharmour (tribal) is situated at an altitude of 2,134 metres in Budhil valley (32.26°N 76.32°E) in the southeast of the district Chamba (Himachal Pradesh).[11] This region is inhabited by a distinct tribe of nomadic pastoralists, known as gaddis. They travel from one ecological zone to another in the winter and summer. The gaddis generally migrate to the lower hills and plains, along with their flock of sheep and goats due to the unfavorable climatic conditions (3-4 months of heavy snowfall in the winter).[12]

Haroli (rural) is situated in Una district of Himachal Pradesh. Its terrain is generally plain with an average elevation of 368 metres (31.48°N 76.28°E) with a subhumid tropical climate.[1314]

Dharamshala, Kangra, and Nurpur towns (urban) are situated in Kangra district of Himachal Pradesh. Kangra is located at 32.1°N 76.27°E with an average elevation of 733 metres.[14] Geographically, it is in the wet subtemperate and humid subtropical zones.[14] Dharamsala town has a hilly topography while the towns of Kangra and Nurpur have a relatively plain terrain.

Study design and selection criteria

A population-based, cross-sectional study was conducted. The study covered the entire eligible population (children aged 1-10 years of age) of the selected areas available for participation on the day of survey. However, children with a history of hearing impairment were excluded from the study. No secondary visit was conducted and only de facto population was studied.

All the houses from the selected areas were surveyed by a house-to-house survey to screen children with autism. The research was carried out in two phases: A screening phase and an evaluation phase.

Screening

Instrument

The participants were screened by trained field investigators utilizing the Hindi version of the Indian Scale for Assessment of Autism (ISAA).[15] The Hindi version was developed by means of a systematic, iterative process. Teams of clinicians (neurologists, pediatricians, psychiatrists, and public health specialists), all of whom were bilingual from Himachal Pradesh selected items from the English version and translated them from English to Hindi, with a different group translating them back to English. The selected version was first tested in urban, educated, bilingual volunteers and then pretested in successive groups of 30 illiterate families with children of 1-10 years of age. The Hindi version was then pilot tested on 100 children from a population culturally and linguistically similar to the study population. The version was finally field tested by the field investigator (under supervision by a clinical team) on 350 children 1-10 years of age from the study sample base (Haroli, Kangra, Dharamsala, Nurpur, and Bharmour)

A. Screening phase: Screening also included an assessment of the sociodemographic profile of the participants using a socioeconomic status (SES) pro forma and a behavioral checklist.[1617] There were separate SES pro formas (modified Kuppuswamy for the urban area and modified Prasad scale for the rural and tribal areas) for the urban, rural, and tribal areas. The ISAA has been developed and validated by the National Institute of Mentally Handicapped (NIMH), Ministry of Social Justice and Empowerment, Government of India, for diagnosing and measuring the severity of autism in 2009. This scale is based on childhood-autism rating scale (CARS) and has 40 items divided under six domains – social relationship and reciprocity; emotional responsiveness; speech, language, and communication; behavior patterns; sensory aspects; and cognitive component. The items are rated from 1 to 5 with an increased score indicating increased severity of the problem. A score of <70 indicates no autism, 70-106 mild autism, 107-153 moderate autism, and >153 severe autism. The screening instrument was administered by investigators trained in the diagnosis of autism.

Training

A training workshop in the assessment of “autism” for investigators and clinical psychologists was specially designed. The training workshop comprised theory (lectures) and clinical posting (in pediatrics). The training program was conducted by a neurologist, psychiatrist, pediatrician, and three public health specialists. The training workshop was followed up by field testing as detailed above.

B. Evaluation phase: After the screening phase, all the subjects who were scoring above 70 on the ISAA were considered suspected cases of autism and were evaluated by a clinical psychologist (VK) and a public health specialist (SKR). The evaluation included an account of the prenatal conditions, birth history, developmental and medical histories, findings from earlier evaluations (including history of hearing impairment), and intellectual and behavioral functioning. The clinical evaluation also included observing the child for a few minutes. The screening scores on the scale were also reconsidered and altered (wherever required). Further, 10% of all the children who scored less and were thus classified as nonsuspects for autism were also evaluated.

Results

A total of 11,000 (children in the age group of 1-10 years) participants were screened. The details of the demographic profile of the population sample studied are shown in Table 1. The table shows that 53.56% and 44.63% of the studied population in the rural area belonged to the “middle class” and “lower middle class,” respectively, on SES scales. In the tribal area, a total of 94.88% of the population sample belonged to the “middle class” on SES. The sociodemographic profile of the urban population shows that 53.83% belonged to the “lower middle class” while 32.1% belonged to the “middle class.” The number of participants who were screened to be positive on the assessment tool (above 70) are shown in Table 2. The total number of such participants was 34. Twenty five of them were from the rural area, five were from the tribal area, and four were from the urban area. The clinical evaluation labeled a total of 10 children as cases of ASD, giving us an overall prevalence of 0.9/1000. Out of these 10, three children belonged to the urban area, five belonged to the rural area, and two children belonged to the tribal area. The sociodemographic details of the diagnosed cases are also shown in Table 2.

Table 1

Showing the number of participants in the study

Selected area	Number of subjects	Female (%)	Male (%)
Urban	4200	1875 (44.64)	2325 (55.3)
Rural	4750	2963 (62.3)	1787 (37.6)
Tribal	2050	919 (44.8)	1131 (55.1)
Total	11000	5757 (52.3)	5243 (47.6)

Table 2

Distribution of the study subjects according to the ISAA score in the population sample

Selected area	Urban			Rural			Tribal
	M	F	T	M	F	T	M	F	T
Subjects scoring >70	3	1	4	11	14	25	2	3	5
Diagnosed cases	3			5			2
SES Classification of diagnosed cases	1: Upper middle			2: Middle class			1: Middle class
	2: Lower middle			3: Lower middle			1: Lower middle

M = Male, F = Female, T = Total

Importantly, none of the children out of the selected random samples of negatively tested children was found positive for ASD.

Discussion

The data represents preliminary findings, based on a mid-term report submitted to the funding agency.

ASD is a clinically defined behavioral syndrome that manifests in early childhood.[18] The core symptoms of ASD include abnormal or unreciprocated interpersonal and emotional interactions, disordered language and communication, and repetitive and stereotypic behavior.[19] It is a condition affecting populations worldwide.[7] The global burden of autism is currently unknown. Most of the studies conducted since the year 2000 in different geographical regions of the world show an estimate prevalence rate of 17/10,000 for autistic disorder and 62/10,000 for all pervasive developmental disorders.[20]

The findings from this study show that six out of the 10 (60%) autistic cases belong to the “lower middle class” on SES. The fact that socioeconomic status is one of the fundamental indicators of ASD is corroborated by our findings.[21] There is a strong and consistent correlation between socioeconomic conditions and mental illness.[22] There is also evidence that the association of SES and health occurs at every level of the socioeconomic hierarchy.[23] Low parental SES is associated with an increased prevalence of autistic traits among children screened 36 months after birth according to a Norwegian mother and child cohort study.[24] Risk factors such as home delivery and birth asphyxia were also reported in many of the subjects on evaluation. It has been documented also that obstetric conditions, along with prenatal and perinatal conditions, are associated with an increased risk for autism and ASDs.[25] Parents/caregivers also gave a history of delay in developmental milestones, specifically motor and speech. Children with autism have been documented in many studies to have lagged in gross motor and language development during the initial months of life.[26]

Two diagnosed cases (females) in the rural area also had comorbidity in the form of seizures. An association between epilepsy, mental retardation, and autism has been reported in many studies.[27]

Research in autism in India has been largely restricted to hospital settings or in selective settings of autistic children and an extensive PubMed search has yielded no results on the prevalence of autism in India.[28293031] One study from Chandigarh, India reflects on the application of ISAA in the child guidance clinic.[31] We found ISAA easy to administer. In spite of finding some difficulty in scoring the items grouped under the emotional responsiveness category, the authors conclude that the scale is useful and feasible for use in routine clinical settings. The use of the scale would pave the way for addressing the longstanding concerns about the identification and quantification of autism and to rate the associated disability in the Indian population.[31]

The findings also suggest abnormal brain developmental processes early in the clinical course of autism. At present, research is underway to better elucidate the mechanisms underlying these structural abnormalities and their longitudinal progression.[19] Brain structural abnormalities need to be worked upon in detail to estimate the true prevalence of autism.

Financial support and sponsorship

The study has been funded by a research grant from ICMR.

Conflicts of interest

There are no conflicts of interest.