Prospective cohort study of vitamin D and autism spectrum disorder diagnoses in early childhood
Authors: Ali Yamna , Anderson Laura N , Smile Sharon , Chen Yang , Borkhoff Cornelia M , Koroshegyi Christine , Lebovic Gerald , Parkin Patricia C , Birken Catherine S , Szatmari Peter , Maguire Jonathon L ,   on behalf of the TARGet Kids! Collaboration, Birken Catherine S. , Maguire Jonathon L. , Lau Eddy , Laupacis Andreas , Parkin Patricia C. , Salter Michael , Szatmari Peter , Weir Shannon , Anderson Laura N. , Borkhoff Cornelia M. , Dai David W.H. , Kowal Christine , Mason Dalah , Abdurrahman Murtala , Anderson Barbara , Anderson Kelly , Arbess Gordon , Baker Jillian , Barozzino Tony , Bergeron Sylvie , Bhagat Dimple , Blanchette Nicholas , Bloch Gary , Bonifacio Joey , Bowry Ashna , Brown Anne , Bugera Jennifer , Calpin Caroline , Campbell Douglas , Cheema Sohail , Cheng Elaine , Chisamore Brian , Constantin Evelyn , Culbert Erin , Danayan Karoon , Das Paul , Beth Derocher Mary , Do Anh , Dorey Michael , Doukas Kathleen , Egger Anne , Farber Allison , Freedman Amy , Freeman Sloane , Gazeley Sharon , Guiang Charlie , Ha Dan , Hafiz Shuja , Handford Curtis , Hanson Laura , Harrington Leah , Hatch Hailey , Hughes Teresa , Jacobson Sheila , Jagiello Lukasz , Jansz Gwen , Jasuja Mona , Kadar Paul , Kiran Tara , Kitney Lauren , Knowles Holly , Kwok Bruce , Lakhoo Sheila , Lam-Antoniades Margarita , Lau Eddy , Leung Fok-Han , Li Alan , Li Patricia , Loo Jennifer , Louis Joanne , Mahmoud Sarah , Malach Jessica , Male Roy , Mascoll Vashti , Meret Aleks , Moodie Rosemary , Morinis Julia , Nader Maya , Nash Katherine , Naymark Sharon , Owen James , Parry Jane , Peer Michael , Pena Kifi , Perlmutar Marty , Persaud Navindra , Pinto Andrew , Porepa Michelle , Qi Vikky , Ramji Nasreen , Ramji Noor , Rana Jesleen , Raza Danyaal , Rosenthal Alana , Rouleau Katherine , Saunderson Janet , Saxena Rahul , Schiralli Vanna , Sgro Michael , Shuja Hafiz , Shepherd Susan , Smiltnieks Barbara , Srikanthan Cinntha , Taylor Carolyn , Turner Suzanne , Uddin Fatima , van den Heuvel Meta , Vaughan Joanne , Weisdorf Thea , Wijayasinghe Sheila , Wong Peter , Wormsbecker Anne , Ying Ethel , Young Elizabeth , Zajdman Michael , Bazeghi Farnaz , Bouchard Vincent , Bustos Marivic , Camacho Charmaine , Dalwadi Dharma , Koroshegyi Christine , Malhi Tarandeep , Thadani Sharon , Thompson Julia , Thompson Laurie , Aglipay Mary , Bayoumi Imaan , Carsley Sarah , Cost Katherine , Eny Karen , Kim Theresa , Kinlin Laura , Omand Jessica , Vanderhout Shelley , Vanderloo Leigh , Allen Christopher , Boodhoo Bryan , Chan Olivia , Hall Judith , Juni Peter , Lebovic Gerald , Pope Karen , Thorpe Kevin , Kandel Rita 
Published: March 2018

Several studies have suggested an association between vitamin D in childhood and autism spectrum disorder. No prospective studies have evaluated whether lower vitamin D levels precede ASD diagnoses – a necessary condition for causality. The objective of this study was to prospectively evaluate whether vitamin D serum levels in early childhood was associated with incident physician diagnosed ASD. A prospective cohort study was conducted using data from preschool-aged children in the TARGet Kids! practice-based research network in Toronto, Canada, from June 2008 to July 2015. 25-hydroxyvitamin D concentration was measured through blood samples and vitamin D supplementation from parent report. Autism spectrum disorder diagnosis was determined from medical records at follow-up visits. Covariates included age, sex, family history of autism spectrum disorder, maternal ethnicity, and neighborhood household income. Unadjusted and adjusted relative risks and 95% confidence intervals were estimated using Poisson regression with a robust error variance. In this study, 3852 children were included. Autism spectrum disorder diagnosis was identified in 41 children (incidence = 1.1%) over the observation period (average follow-up time = 2.5 years). An association between 25-hydroxyvitamin D concentration and autism spectrum disorder was not identified in the unadjusted (relative risk = 1.04, 95% confidence interval: 0.97, 1.11 per 10 nmol/L increase in 25-hydroxyvitamin D concentration) or adjusted models (adjusted relative risk = 1.06; 95% confidence interval: 0.95, 1.18). An association between vitamin D supplementation in early childhood and autism spectrum disorder was also not identified (adjusted relative risk = 0.86, 95% confidence interval: 0.46, 1.62). Vitamin D in early childhood may not be associated with incident physician diagnoses of autism spectrum disorder.