The Rising Prevalence of Autism: A Prospective Longitudinal Study in the Faroe Islands

Abstract

We have followed up a 2002 population study of autism prevalence in 15-24-year olds in the Faroe Islands. The rate of ASD grew significantly from 0.56% in 2002 to 0.94% in 2009. Although these results are within the range of typical findings from other studies, there were some interesting details. There were-in addition to 43 originally diagnosed cases in 2002-24 newly discovered cases in 2009 and nearly half of them were females. It is possible that unfamiliarity with the clinical presentation of autism in females have played a significant role in this context. There was diagnostic stability for the overall category of ASD over time in the group diagnosed in childhood (7-16) years, but considerable variability as regards diagnostic sub-groupings.

Vitamin D in the General Population of Young Adults with Autism in the Faroe Islands

“…Our findings are consistent with those of several studies published since 2010, although some of these had methodological problems e.g., no comparison group or a problematic comparison group (Nseir et al 2012; Kočovská et al 2012a, b) (see “Appendix”).…”

“…Although some degree of genetic relatedness in the Faroe Islands can be assumed—due to the small population and its genetic isolate character, the prevalence of autism in the Faroe Islands has been found to be similar to other western nations, namely 0.56 % in 2002 (Ellefsen et al 2007) and 0.94 % in the follow up study in 2009 (Kočovská et al 2012a, b). The fact that in the follow up screening process an additional 24 individuals were diagnosed with autism, who were originally missed, and nearly half of these were females (n = 11), supports the findings of other studies, suggesting that girls are often missed at a young age and that screening and diagnostic processes need to address this phenomenon in the future (Giarelli 2010; Kočovská et al 2013).…”

“…Participants with ASD were recruited during a two-phase screening process of the entire Faroe Islands population (n = 47,962) in the relevant school age group (7–16 years, n = 7,689) for the study of ASD prevalence in the Faroe Islands in 2002 (Ellefsen et al 2007) (n = 43) and 2009 (n = 24) (Kočovská et al 2012a, b). Thus the 67 individuals diagnosed with ASD represent an entire age-cohort of individuals with ASD in the Faroe Islands and therefore the present study represents the first ever entire population sample of vitamin D levels in ASD population.…”

“…There are several known risk factors including a variety of mutated and variant genes, advanced paternal age, exposure to toxins and medications in early development, prematurity, and birth complications (Kolevzon et al 2007; Gardener et al 2009; Coleman and Gillberg 2012; Munger et al 2012; Cannell and Grant 2013). Recently, maternal/neonatal vitamin D deficiency has been proposed as a possible environmental risk factor for ASD (Cannell and Grant 2013; Grant and Soles 2009; Kočovská et al 2012a, b) due to its involvement in early neurodevelopment (Eyles et al 2013), the immune system (Hayes et al 2003), and gene regulation (Ramagopalan et al 2010) processes.…”

Vitamin-D Deficiency As a Potential Environmental Risk Factor in Multiple Sclerosis, Schizophrenia, and Autism

“…The latter enzymatic hydroxylation reaction, producing calcitriol, has also been found to occur in lymphocytes and in the brain in microglia and probably in other locations (16). The half-life of calcidiol, which is dependent on vitamin-D-binding protein concentrations and genotype, is approximately 15 days and serves as a clinical measure of vitamin-D status, whereas the half-life of calcitriol is much shorter (5–15 h), therefore, its local production is advantageous (11, 17). …”