Kviksilvur dálking og D-vitamin støði í móðurlívi – sambandið millum hesi og autismu.
Deildin fyri Arbeiðs- og Almannaheilsu
Pál Weihe, Guðrið Andorsdóttir, Christopher Gillberg, Tórmóður Stórá, Flemming Nielsen, David Hougaard
01.03.17 – 31.12.19
Stuðul úr Granskingargrunninum:
Granted: 193.650 kr.
Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder, with multiple genetic and possible environmental risk factors including vitamin D deficiency and methyl mercury exposure. The interplay between genetic and environmental factors has become the subject of intensified research in the last several years.
Vitamin D deficiency – either during pregnancy or early childhood – has recently been proposed as a possible environmental risk factor for ASD. Due to the high northern latitude the population of the Faroe Islands are at greater risk for vitamin D deficiency and therefore the association between prenatal vitamin D levels and autism is very natural and important to investigate. Another environmental factor also suspected to be associated with autism and highly interesting studying in The Faroe Islands is methyl mercury exposure. The Faroese people have shown to be heavily exposed to this toxic metal due to high intake of pilot whale known to contain substantial quantities of mercury. Several studies - included Faroese studies - have reported significant associations between prenatal exposure to mercury from some seafood, including fish, in the maternal diet and an increased risk of adverse effects on the child’s neurodevelopment.
The Faroese autism study was initiated in 2000. A representative cohort was identified when all 65 schools in the Faroe Islands were screened for autism spectrum disorders (ASD). This group consisted of 7,689 children (3,895 boys and 3,794 girls) aged between 8 and 17 years. From this group a total of 43 children were screened positive for autism characteristics (0.56%) – childhood autism, Asperger syndrome or atypical autism. In 2008-09 the whole cohort was re-assessed in a follow-up study screening the same group individuals now being between 15 to 24 years old. Several new cases (N=24) were diagnosed who had been missed at the time of the original study, given a total number of 67 (1%) cases in the Faroese autism cohort. During the follow up study in 2009 the cohort was extended to also include family members of the cases and age and sex matched controls.
This project is an extension of the existing Faroese autism project and is therefore based on the same cohort – both cases and controls.
The hypotheses are that prenatal exposure to methyl mercury and insufficient prenatal vitamin D levels are associated with autism. Hence the aim of this study is to measure prenatal methyl mercury levels and prenatal vitamin D levels in blood on filter paper from 55 Faroese ASD cases and 236 controls and compare the measurement in the two groups.
Autism spectrum disorder (ASD) affects about 1% of the world’s population. Vitamin D is thought to be essential for normal brain development and prenatal vitamin D deficiency has attracted interest as a possible risk factor for ASD as well as other neurodevelopmental disorders. Another environmental factor proven to have increased risk of adverse effects on the child’s neurodevelopment is methyl mercury.
The prenatal levels of vitamin D and methyl mercury were measured in blood on filter papaer from 29 ADS cases and 160 age-matched controls.
No significant difference in mean 25(OH)D was found between the ASD cases (27.0 nM, SD=12.7) and the control group (25.5 nM, SD=10.9). For both cases and controls the mean 25(OH)D levels did not vary according to the season of the year in which they were sampled (cases: p=0.59 and controls: p=0.24). Further the difference in season of birth between cases and controls was not significant (p=0.355).
Further no significant difference was found in the levels of methyl mercury in cases (36.1 µg/L, SD=27.2) and controls (33.0 µg/L, SD=20.6).
This study does not support the hypothesis that insufficient 25-hydroxyvitamin D levels at birth is a risk factor for autism or that prenatal methyl mercury expossure is associated with autism.. The small sample size is a limitation and it would have been an advantage to use siblings as a joint environmental and genetic control group.
The results still need to be published in scientific articles, but data has been presented at scientific conferences as posterpresentations:
ESSENCE - coference in Gothenburg April 2018
PPTOX – conference in Torshavn May 2018
Granskingardagur á LS – May 2018