World Health Organization
منظمة الصحة العالمية
Organisation mondiale de la Santé

Epidemiology of autistic disorder in Bahrain: prevalence and obstetric and familial characteristics

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A.M. Al-Ansari 1 and M.M. Ahmed 2

وبائيات اضطراب الذاتوية (التوحُّد) في البحرين: معدل الانتشار والخصائص العائلية والتوليدية

أحمد مال الله الأنصاري، محمد محمود أحمد

الخلاصـة: أظهرت الدراسات في أوروبا وفي شمال أمريكا أن معدل انتشار الاضطرابات الذاتوية (التوحد) آخذ بالازدياد. وقد أجرى الباحثان هذه الدراسة للتعرف على معدل انتشارها في البحرين، وللتعرف على الخصائص الديمغرافية والأسرية لها. واستخدم الباحثان تصميماً للحالات والشواهد، وشملت دراستهما 100 طفل شخصوا على أنهم مصابين باضطراب الذاتوية (التوحُّد) وفقاً للدليل التشخيصي والإحصائي للاضطرابات النفسية، بطبعته الرابعة، ونَصّه المنقّح (DSM-IV-TR)، وذلك في الفترة بين 2000 و2010. واختار الباحثان عدداً متساوياً من الشواهد الذين تم تشخيصهم على أنهم مصابون بسلس البول الليلي دون أن يكون لدى أيٍّ منهم اعتلال نفسي، مع توافقهم من حيث الجنس والعمر مع الحالات. وقدَّر الباحثان معدل انتشار الاضطراب الذاتوي (التوحُّد) بنسبة 4.3 لكل 10000 نسمة، وكانت نسبة الذكور إلى الإناث 4 إلى 1. واتضح للباحثين أن عدد الحالات التي ولدت بالقيصرية أكثر من عدد الشواهد، وأن أمهاتهم قد عانوا من مضاعفات قبل الولادة أكثر من الشواهد وذلك بمقدار يعتدّ به إحصائياً. وكان تقدير معدل الانتشار في البحرين مماثلاً لما ورد في تقارير سابقة اتبعت نفس الطرق. واستنتج الباحثان أن المضاعفات التوليدية والولادة بعملية قيصرية يمكن أن تترابط بالاضطراب الذاتوي (التوحُّد).

ABSTRACT European and North American studies show that the prevalence of autistic disorder is increasing. This study was performed to identify the prevalence of autistic disorder in Bahrain, and determine some of the demographic and family characteristics. Using a case–control design, 100 children who received a diagnosis of autistic disorder according to DSM-IV-TR during the period 2000–2010 were selected. An equal number of controls who had received a diagnosis of nocturnal enuresis and no psychopathology were selected, matched for sex and age group. The prevalence of autistic disorder was estimated as 4.3 per 10 000 population, with a male:female sex ratio of 4:1. Significantly more cases than controls were delivered by caesarean section and had mothers who suffered prenatal complications. The prevalence estimate in Bahrain is comparable to previous reports using similar methods. Obstetric complications and caesarean section delivery may be associated with autistic disorder.

Épidémiologie du trouble autistique à Bahreïn : prévalence et caractéristiques obstétricales et familiales

RÉSUMÉ Des études européennes et nord-américaines indiquent que la prévalence du trouble autistique est en augmentation. La présente étude a été réalisée afin de connaître la prévalence du trouble autistique à Barheïn, et de déterminer certaines caractéristiques démographiques et familiales. À l'aide d'un plan d'étude cas-témoins, 100 enfants ayant reçu un diagnostic de trouble autistique selon le Manuel diagnostique et statistique des troubles mentaux (quatrième édition) au cours de la période 2000-2010 ont été sélectionnés. Des témoins en nombre équivalent ayant reçu un diagnostic d'énurésie nocturne mais qui étaient exempts de psychopathologie ont été sélectionnés, appariés pour le sexe et la tranche d'âge. La prévalence du trouble autistique a été estimée à 4,3 pour 10 000 dans la population, avec un rapport de masculinité de 4 pour 1. Le nombre de nourrissons nés par césarienne et dont la mère avait souffert de complications prénatales était nettement supérieur dans le groupe des cas par rapport aux témoins. L'estimation de la prévalence à Bahreïn était comparable aux rapports antérieurs ayant utilisé des méthodes similaires. Des complications obstétricales et une naissance par césarienne pourraient être associées à un trouble autistique.

1Department of Psychiatry, College of Medicine and Medical Sciences, Arabian Gulf University, Manama, Bahrain (Correspondence to A.M. Al-Ansari: This e-mail address is being protected from spambots. You need JavaScript enabled to view it ).
2Department of Ear, Nose and Throat, Head and Neck, King Hamad University Hospital, Al Muharraq, Bahrain.
Received: 18/04/12; accepted: 19/06/12
EMHJ, 2013, 19(9):769-744

Introduction

Autistic disorder is a chronic and severe neurodevelopmental disorder characterized by impairments in social interaction, reciprocal communication, patterns of stereotyped behaviour and onset before age 3 years [1]. Although its etiology remains unknown, there is evidence to suggest that it is common among the same families and possibly influenced by environmental factors [2,3]. Prevalence estimates have increased in the last 2 decades and range from 0.7 per 10 000 population to 72.6 per 10 000 with a mean of 20.6 per 10 000. According to the Centers for Disease Control’s Autism and Developmental Disabilities Monitoring Networkabout 1 in 88 children in the United States of America (USA) is identified with autism spectrum disorder [4]. The mean male:female ratio is 4.2:1 [5]. Factors playing a major role in this increase in prevalence include broadening of the definition of autistic disorder and improved awareness of the disorder with a concomitant development of services; other factors such as sample size, publication year and geographic location of the studies play a role in variations in estimates [6–8].

In the 1990s autistic disorder was rarely referred to or diagnosed in the Child and Adolescent Psychiatric Unit (CAPU) in Bahrain. In the last 5 years, however, autistic disorder is diagnosed on weekly basis and today CAPU uses a set of formal instruments for autistic disorder diagnosis. To the author’s knowledge, the prevalence of autistic disorder was never estimated in Bahrain. Studies on the prevalence of autistic disorder in the region are scarce. In Oman Al-Farsi et al. in 2011 reported an autistic disorder estimate of 1.4 per 10 000 with a male:female ratio of 4:1 [9].

The present study was a part of prospective case–control study investigation of the relationship between autistic disorder and advancing parental age. In this paper we report an estimate of the prevalence of autistic disorder in Bahrain, together with the sex distribution and possible associated factors such prenatal and postnatal complications, type of delivery and other personal and familial characteristics.

Methods

Study setting

Bahrain is an archipelago situated in the Gulf region, east of Saudi Arabia. It covers an area of approximately 750 km2, and has an estimated population of 1.25 million in 2010. Health services are free and accessible to all residents. The country is characterized by a low infant mortality rate, 7.2 per 1000, and high life expectancy of 74.8 years.

Annually, nearly 30 new cases of autistic disorder are diagnosed in CAPU, the only referral unit for autistic disorder in Bahrain, and referred to 3 community centres that care for autistic disorder. In the school year 2010–11 a small group of autistic disorder children were integrated into the regular public school system. The centres can accommodate around 120 autistic disorder persons aged 2–21 years. Youths above the age of 21 years can join an afternoon social club that is open 6 days a week.

Study design and sample

The prevalence of autistic disorder was estimated by dividing the number of cases (100) by the Bahraini population for 2005 multiplied by 100 000.

The study of associated factors utilized a case–control design. The study group were all cases attending the CAPU, the Alwafa centre, Al Rashad centre and youth club, who received a diagnosis of autistic disorder over the time period 2000–10 and who met the inclusion criteria (n = 100). The diagnosis was reached according to the Modified Checklist for Autism in Toddlers [9], the Diagnostic and Statistical Manual of Mental Disorders (4th edition, text revision) [10] and the Childhood Autism Rating Scale [11]. The control group consisted of an equal number of children and youths attending the unit over the same time period, randomly selected from a pool of 350 individuals matched for age (in 5-year age groups), sex, social class, parent's education and family history. The controls were children and youths receiving a diagnosis of nocturnal enuresis (n = 64), mild behaviour disorder (n = 10) and no psychopathology (n = 26). The study received the approval of the ethics committee of the Ministry of Health of Bahrain.

Data collection

Medical records from CAPU and social records from participating centres were reviewed by the co-author and related data were abstracted. The data were entered into a form specially designed for the study by a co-author. The items on the form aimed to collect data on child’s age and sex, birth order, language development (based on parent’s reports), sleeping and eating patterns, and on the mother’s pregnancy and delivery, including duration of pregnancy (term or preterm), type of delivery (normal, lower segment caesarean section or assisted delivery), and any prenatal, natal and postnatal complications and stressful life events around the time of delivery (based on parents reports). The parents’ section included age at birth of the child, educational level, employment, family history of autistic disorder, consanguinity (1st or 2nd degree) and any history of psychiatric or medical disorders (based on parents’ reports) The social class was constructed following Hollingshead and Redlich’s 5-point scale [12].

Neither the cases nor their parents were interviewed. Parents of 9 cases and 21 controls were contacted by telephone or home visits by the CAPU social worker to complete some missing data. All parents gave informed consent prior to inclusion in the study. Only 1 case from the study group was excluded due to doubtful diagnosis.

Analysis

The data were entered and analysed using SPSS, version 16.0. The data were presented as simple frequencies and mean and standard deviation (SD). Odds ratios (OR) were calculated and the chi-squared test of significance was used to assess differences between cases and controls wherever applicable.

Results

Prevalence

The case register method revealed a prevalence of 4.3 per 10 000 population using an estimated Bahraini population for the year 2005.

Characteristics of autistic disorder cases

Table 1 shows that males outnumbered females among cases by a ratio 4:1. The mean age was 10.5 (SD 6.4) years, range 2–27 years. One-third presented with sleep and eating disorders (39% and 30% respectively). Speech was totally absent in 38% of cases, 64% had some language production and 15% were able to communicate occasionally using short sentences. The great majority of mothers (83%) did not report any stressful events during pregnancy, delivery and the early postpartum period. Nearly one-third of autistic disorder cases (29%) had blood-related parents.

Table 2 shows that more than three-quarters of parents had received either high school or college education (77% mothers and 82% fathers). Most fathers were employed while 68% of mothers were housewives; 10% of fathers were retired. A family history of autistic disorder was present in 12% of the studied families. A small number of families (7%) reported the presence of psychiatric disorders among parents compared with 12% with chronic physical disorders. The majority of cases (85%) came from the lower social classes 4 and 5.

Case–control comparisons: mother’s pregnancy and birth history

Cases did not differ from controls in the mother’s duration of pregnancy and rate of postnatal complications (Table 3). However autistic disorder cases had a significantly higher incidence of delivery complications (i.e. lower caesarean section or assisted delivery) (24% versus 12% for controls, OR = 2.51, 95% CI: 1.12–5.63) (P = 0.025). In addition 15% of mothers of autistic disorder cases had prenatal complications compared with 4% control cases (OR = 4.19, 95% CI: 1.34–13.1) (P = 0.014).

Discussion

Results from this case register study in Bahrain estimated a prevalence of autistic disorder of 4.3 per 10 000, which is similar to other studies using similar data collecting methods [5,13–18]. This rate is nearly 4-fold the rate reported from the Gulf region [19]. In spite of the fact that the case register method is usually accused of underestimation [20], the authors do not believe that this applies to our study. First, because the coverage of services by our unit involves all the islands of Bahrain, as CAPU is located in a central area and people reside within 10 km in either direction. Secondly, the level of awareness among professionals and the population is high as CAPU receives on a daily basis children referred with delays in language development from the network of 24 health centres attached to the main general hospital. Thirdly, all suspected cases of autistic disorder are assessed in CAPU by one team and so case definition does not present an obstacle. However, we do believe that a small number of cases within wealthy families are treated abroad, and that there may be other unidentified individuals with autistic disorder who have higher intellectual functioning and who might escape detection and enter directly to the public school system.

The background characteristics of the cases revealed an overall male:female sex ratio of 4:1, in line with many other studies [7]. The proportion of cases (62%) who had some language production is considered high. This could be explained by the fact that many cases had received several years of extensive training in communication skills and by the wide range of ages studied. The rate of sleep and eating disturbances among cases (39% and 30%) was lower than figures of 44%–88% and 90% reported by other studies [21,22]. The prevalence of stressful life events is probably similar to that in the society at large and is considered to be relatively small.

The figure for consanguinity among the parents of autistic disorder cases seems to be high (29%). The overall rate of consanguinity in Bahrain is declining over time; at present it is around 15%, which is a decrease from the higher level of 39% in 1996 [23]. The figure of 29% is probably typical for parents who got married in the 1990s and not for the present population. Consanguinity was found to be an associated factor for mild intellectual disability in a community-based, case–control study [24]. In the present study, we did not compare this factor with the control group because we controlled for social class (which is to some extent a proxy for consanguinity) because of its relevance to both groups.

The rate of family history of autistic disorder among the relatives of cases (12%) supports the role of genetic factors, which has been suggested by other studies [25]. The prevalence of psychiatric disorders was not compared between the relatives of cases and controls. The types of disorders could not be investigated further. The majority of parents of cases were healthy individuals.

In the case­–control comparisons prenatal obstetric complications (OR = 4.19) as well as caesarean section/assisted delivery (OR = 2.51) were significantly more common among cases; this finding is in accordance with other reported studies [25]. The rate of caesarean section deliveries among cases (24%) exceeded the acceptable rate of 15% suggested by the World Health Organization [26] and a recent report from the main referral general hospital in Saudi Arabia [27].

The study had some limitations. The nature of the study design being a retrospective analysis of events has its own known limitations. Ideally, the control group should be derived from a representative community cohort, as estimates of autistic disorder calculated by case–controlled studies will not be the same as those derived from population-based studies. Other limitations include lack of comparable data from the region and the unavailability of some data such as age of marriage and rates of obstetric complications.

Conclusions

The present study adds to the available knowledge regarding an important public health concern in the Eastern Mediterranean Region. The prevalence of autistic disorder in Bahrain was within the range reported by other studies using similar method. Boys outnumbered girls by a ratio of 4 to 1. Risk factors associated with autistic disorder were prenatal complications and caesarean section/assisted delivery. Future research should be directed towered studying risk factors derived from a population-based sample, and evaluation of rehabilitation efforts.

Funding: None

Competing interests: None declared.

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