Kočovská, Eva (2014) A population study of risk factors for autism spectrum disorders in the Faroe Islands PhD thesis http://theses.gla.ac.uk/5555/ Copyright and moral rights for this thesis are retained by the author A copy can be downloaded for personal non-commercial research or study, without prior permission or charge This thesis cannot be reproduced or quoted extensively from without first obtaining permission in writing from the Author The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the Author When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given Glasgow Theses Service http://theses.gla.ac.uk/ theses@gla.ac.uk A Population Study of Risk Factors for Autism Spectrum Disorders in the Faroe Islands Eva Kočovská School of Medicine College of Medical, Veterinary and Social Studies A thesis submitted in part fulfilment of the requirements of the degree of Doctor of Philosophy September 2014 To Elizabeth and Veronica ABSTRACT Objectives: To study autism spectrum disorder (ASD) in the Faroe Islands, including prevalence, diagnostic stability and environmental factors that are potentially involved in the aetiology of autism Method: I The target group was recruited from the entire population sample of participants with ASD during a two-phase screening and diagnostic process of the entire Faroe Islands population in the relevant school age group born between 19851994 (7-16 years, n=7,689) in 2002 and again in 2009 (15-24 years, n= 7,128) using an independent clinical diagnosis and standardised tools II The diagnostic stability of ASD from childhood to early adulthood over a period of years compared diagnoses in 2002 and 2009 III A literature search of vitamin D and ASD covering the period from January 1995 to October 31 2011 was carried out IV A pilot study involved questioning 20 mothers of young individuals from the target group and 13 mothers of healthy comparisons, regarding mothers‘ diet habits, health, lifestyle and well-being during their pregnancy with an index child V 25hydroxyvitamin D3 (25(OH)D3) levels were examined in a population based crosssectional study that involved 219 individuals: 40 participants with a diagnosis of ASD from the target group (31 males/9 females), their 62 typically developing siblings (29 brothers/33 sisters), their 77 parents (40 mothers/37 fathers), and 40 healthy comparisons (28 males/12 females) Results: I The rate of ASD rose significantly from 0.56% (n=43) in 2002 to 0.93% (n=66) in 2009 Although these results were still within the range of typical findings from other studies, of the 24 newly discovered cases in 2009 nearly half were females thus altering the male/female ratio from 6/1 to 2.7/1 II The stability of clinical ASD diagnosis was perfect for AD, good for ―atypical autism‖/PDD-NOS, and less than perfect for Asperger syndrome (AS) Stability of the diagnoses made by means of research tools were more variable but still good for AD Both systems showed excellent stability over the seven-year period for ―any ASD‖ diagnosis, although a number of clear cases (especially in females) had been missed in the original screening in 2002 These results support the notion that a single overarching diagnostic category, ‗autism‘ or ASD, would better suit clinical realities as outlined in the new DSM-5 III The systematic review (in 2010) provided some, albeit very limited, support for the possible role of vitamin D deficiency in the pathogenesis of ASD: there are three main areas of involvement of vitamin D in the human body that could potentially have direct impact on the development of ASD: (1) the brain, (2) gene regulation and (3) the immune system The prevalence of ASD has been suggested to be raised at higher latitudes IV Mothers of individuals with ASD had had during their pregnancy significantly less positive ―attitude to sun‖ (p=0.001), consumed fewer vegetables (p=0.026) and also less fruit (p=0.078) V The ASD case group had significantly lower 25(OH)D3 levels (24.8 nmol/L) than their typically-developing siblings (42.6 nmol/L, p