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Risk Factors for Autism Spectrum Disorders in the Faroe Islands

In this edition of the Researcher’s Corner we meet Dr Eva Kočovská PhD for a talk about her recently defended dissertation titled A Population Study of Risk Factors for Autism Spectrum Disorders in the Faroe Islands.

The dissertation presents the results of a population-based study on autism (ASD) conducted in the Faroe Islands. Autism is as common in the Faroe Islands – a genetic isolate – as in the rest of the Western world. A higher worldwide prevalence of ASD diagnosis in recent years that cannot be explained by genetics has spurred a search for other factors that might play a part in the development of ASD. In this process the gene-environment interplay has come into play as the focus of intensified ASD research. One possible environmental risk factor for ASD that has been suggested is vitamin D deficiency during pregnancy or in early childhood. ASD has a higher reported prevalence in urban areas, areas with high air pollution, cloudy areas and at higher latitudes.

Can you give us some background on the possible connection between vitamin D and increase in ASD diagnosis worldwide in recent years?

- The increase of the reported ASD prevalence over the last 40 years coincides with a dramatic increase in the vitamin D deficiency worldwide. This is related to sun avoidance, which is in turn related to the increasingly indoor urbanised lifestyle and use of sunscreen, and changes in life-style and diet, reducing the intake of vitamin D by more than 50% from fish by frying instead of boiling.

Due to a number of characteristics the Faroese region lends itself particularly well to population-based studies of environmental factors in autism prevalence. Eva explains:

- The Faroe Islands constitute a genetic isolate, which for genetic analysis is a massive advantage. From the perspective of studying environmental exposure, the high latitude position as well as certain socio-demographic conditions - e.g. a very cohesive society in terms of for example diet, lifestyle, health care and schooling - are favourable.

The dissertation consists of articles covering several interrelated issues: the rising reported prevalence of ASD, diagnostic stability from childhood to early adult life, vitamin D and ASD, and dietary and lifestyle habits in pregnancy in the Faroe Islands.

Can you share some of your results of the study on vitamin D and ASD?

- In our first-ever population-based study of vitamin D in ASD we found significantly lower levels of vitamin D in adolescents and young adults with ASD compared with their siblings and parents and also compared with typically developing controls. There are presently five studies conducted in different parts of the world (Egypt, Saudi Arabia, Brazil, China and the Faroe Islands) and all showing significantly lower levels of vitamin D in a population with ASD.

What could these findings be indicative of?

- Vitamin D is involved in early brain development and brain function. It modulates our body’s immune system and regulates genes. The findings could be a reflection of the consequences of ASD per se affecting a person’s lifestyle or diet or of the underlying biology of ASD impacting in some way directly on the metabolism of vitamin D. Alternatively, the low vitamin D levels could point to a life-long vitamin D deficiency in ASD, and this hormone deficiency could have been involved in early development of the brain, causing the development of ASD.
- For future research regarding vitamin D deficiency, the first step would be to treat the deficiency while observing any difficulty in correcting the levels, as such difficulties could indicate potential steroid metabolism impairments.
- The ESSENCE* concept coined by Professor Gillberg in 2010 suggests co-existing developmental deficits in the areas of general development, communication and language, social interrelatedness, motor coordination, attention, activity, behaviour, and mood and/or sleep. To date, Vitamin D deficiency has been shown to be implicated in epilepsy, cognitive/language development, motor coordination, activity/fatigue and mood/sleep disorders. Thus, the vitamin D deficiency appears to be a relevant element in this panorama of ESSENCE syndromes.

In one of your article’s you studied mothers’ attitudes towards the sun as a potential environmental risk factor. What was the main outcome of this study and how did it relate to the other studies?

- We looked at the attitude towards the sun in mothers of children with and without ASD. Most control mothers reported that they had been actively seeking sun during their pregnancy while most mothers of children with ASD said that they had not. The difference in attitude towards the sun is interesting as it can be related to vitamin D levels and possibly indicate some other underlying problems.

Another study in your dissertation deals with diagnostic stability in ASD. Can you tell us something about that study? How was it conducted and what was the result of the study?

- The prevalence rate was measured in 2002 and again in a follow-up in 2009. Between 2002 and 2009 the registered prevalence increased, showing that about 36% of the total cohort had been missed at the initial screening- study, taking place in school-age years. The diagnostic stability of childhood ASD was very good, for atypical ASD good, and for Asperger syndrome not as good. These results support the new development in DSM-V with its single overarching ASD diagnosis.

How could the increase in ASD rates between 2002 and 2009 be explained?

- 49% of the newly diagnosed cohort in 2009 consisted of females, which points to girls being overlooked due to unfamiliarity with the way autism is presented in girls at an early age as the most plausible explanation. The trend in the study was for girls to account for a comparatively larger portion of the missed cases. Almost 2/3 of all the females with ASD were only identified at or after the age of 15, whereas almost ¾ of all males with ASD had been diagnosed before that age.
- The increasing rates of ASD might be attributed in part to the trend of girls being misdiagnosed or missed altogether. This, in turn, is likely to be a result of available screening and diagnostic instruments being developed from a male prototype of ASD and hence not being sensitive enough to detect ASD in girls. Another factor possibly playing a part is that girls show less severe problems in school and for this reason might be at higher risk of going unnoticed.

Could the increased detection of girls also account for the increasing rate of diagnosed ASD worldwide?

- In part, yes. Increased knowledge along with improved screening and diagnostic instruments could account for more individuals, boys and girls, being diagnosed with ASD. Another possible reason behind the higher reported prevalence of diagnosed ASD may be recent developments in perinatal and neonatal care leading to much higher survival rates of pre-term babies, including extremely premature ones. These prematurely born babies present with higher rates of ASD than the general population. The dramatic increase in vitamin D deficiency in people worldwide could also play a part.

What are the implications of your studies for future research and clinical work?

- The results support the notion of unfamiliarity with the clinical presentation of ASD in females at an early age and/or insensitivity of the present diagnostic tools to the female ASD phenotype as one of several reasons behind the soaring rates of diagnosed ASD worldwide.
- ASD requires a holistic approach and lifestyle, diet, and attitude to sun should be checked early on.
- The research results available to date suggest that low vitamin D levels in utero or early postnatal life might interact with other factors to increase the risk for ASD. The results might alert clinicians to the importance of checking vitamin D levels in children with ASD. Every child with ASD should be checked for vitamin D deficiency as part of clinical assessment and treatment. Vitamin D deficiency might be an independent symptom for ASD, indicating the need to examine vitamin D levels/intake in pregnant women and in patients with ASD. Improving vitamin D levels might improve the general health and wellbeing and possible also alleviate some of the ASD symptoms, but this is speculation given that no study has been performed that shows amelioration of autism symptoms after vitamin D supplementation.

* Early Symptomatic Syndromes Eliciting Neurodevelopmental Clinical Examinations

By Nanna Gillberg
 

Page Manager: Anna Spyrou|Last update: 11/26/2014
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