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The time has come for living systematic reviews in autism research

While the inclusion of more recent estimates canimprove accuracy and utility of systematicreviews, there is a key challenge: how can evidence influence policy if it cannot be updated in real time?

Autism prevalence estimates have been used for decadesto inform policy and practice in research and servicedelivery. In our recent systematic review update (Zeidanet al., 2022), we found a large increase in the number ofestimates available relative to the first systematic reviewwe conducted in 2012 (Elsabbagh et al., 2012). Theincrease was most notable in world regions which werelargely unrepresented in the past.

In their Letter to the Editor, Roman-Urrestarazuet al. (2021) argued that a missing study from our review,led to inaccurate estimates for the European region. Wecaution against interpreting prevalence estimates as “groundtruth” but rather as useful snapshots in time of whois being counted or not counted as having autism. In oursystematic review, we comprehensibly examined methodologicalfeatures such as definitions of autism, studydesign attributes, data sources, and sampling procedures that substantially impact prevalence estimates.

Roman-Urrestarazu et al. (2021) is indeed a uniquestudy because it went beyond estimating prevalence toexamining key social determinants modifying prevalencein a large population of school-age children. However,when our search was last updated in November 2021, thepublication from Roman-Urrestarazu et al. (2021)despite being in the database, had not yet been indexed, and was therefore not captured by our literature search.

While the inclusion of more recent estimates canindeed improve accuracy and utility of systematicreviews, there is a key challenge: how can evidence effectivelyinfluence policy if it cannot be comprehensivelyupdated in real time? Traditional systematic reviews likethe one we conducted are time-consuming, costly, andtheir results necessarily lag behind. The proliferation ofepidemiological literature all over the world amplifies thechallenge of maintaining prevalence estimates up to date.

To illustrate this point, we reran our search on March16, 2022. Not surprisingly the updated search identifiedRoman-Urrestarazu et al. (2021) embedded within alarge number of 267 articles published in this area only inthe last few months (Supporting Information, Figure S1). We went further and screened these articles to check if they contained new epidemiological estimates. Indeed, we identified not one but eight new estimates in different world regions. As expected, our global estimates remain largely similar with the addition of the new estimates but regional estimates were more susceptible to change onlyin those regions where fewer estimates are available (Table 1).

Summary of autism prevalence estimates across world regions from 2012 to 2022 (updated search on March 16, 2022).
Open file to view table:PDF icon The time has come for living systematic reviews in autism research

We believe that the utility of systematic reviews lies in the transparency of the search and availability of all the data extracted (Supporting Information, Tables S1 and S2). As we did here, researchers and knowledge users can reuse the extracted data to perform updates, more targeted analyses such as regional ones, and new analyses such as economic estimates.

Another solution is on the horizon. A new review format has been developed (Elliott et al., 2014) and implemented in a number of journals (Rahal et al., 2016) leading to a Cochrane guidance (Cochrane Community, 2019). A “living systematic review” is one that is updated continually to include new evidence. Key to its success is commitment to monthly updates of the search, inclusion, and interpretation of new evidence. The time has come for living reviews in autism research.

Letter to the editor on May 15, 2022.


Data availability statement
The data that supports the findings of this study areavailable in the supplementary material of this article
Mayada Elsabbagh1
Afiqah Yusuf1
Jinan Zeidan1
Julie Scorah1
Eric Fombonne2
Maureen S. Durkin3
Shekhar Saxena4
Andy Shih5
1Montreal Neurological Institute-Hospital, Faculty of Medicine & Health Sciences, ۲ݮƵ University, Montreal, Canada
2Department of Psychiatry, Oregon Health and Science University, Portland, Oregon, USA
3Population Health Sciences, Department of Pediatrics, Waisman Center, University of Wisconsin-Madison,Madison, Wisconsin, USA
4Department of Global Health and Population, Harvard T H Chan School of Public Health, Boston,Massachusetts, USA
5Science, Autism Speaks, New York City, New York, USA
Correspondence
Mayada Elsabbagh, Montreal NeurologicalInstitute-Hospital, Faculty of Medicine & HealthSciences, ۲ݮƵ University, 3775 Rue University,Room C18, Montreal, Quebec H3A 2B4, Canada.
Email: mayada.elsabbagh [at] mcgill.ca
ORCID
Mayada Elsabbagh
Andy Shih
References
Cochrane Community. 2019. Guidance for the production and publicationof Cochrane living systematic reviews: Cochrane reviews inliving mode - version December 2019.
Elliott, J. H., Turner, T., Clavisi, O., Thomas, J., Higgins, J. P. T.,Mavergames, C., & Gruen, R. L. (2014). Living systematicreviews: An emerging opportunity to narrow the evidence-practicegap. PLoS Medicine, 11(2), e1001603.
Elsabbagh, M., Divan, G., Koh, Y.-J., Kim, Y. S., Kauchali, S.,Marcín, C., Montiel-Nava, C., Patel, V., Paula, C. S., Wang, C.,Yasamy, M. T., & Fombonne, E. (2012). Global prevalence ofautism and other pervasive developmental disorders. AutismResearch, 5(3), 160–179.
Rahal, A. K., Badgett, R. G., & Hoffman, R. M. (2016). Screening coverageneeded to reduce mortality from prostate cancer: A livingsystematic review. PLoS One, 11(4), e0153417.
Roman-Urrestarazu, A., van Kessel, R., Allison, C., Matthews, F. E.,Brayne, C., & Baron-Cohen, S. (2021). Association ofRace/ethnicity and social disadvantage with autism prevalence in7 million school children in England. JAMA Pediatrics, 175(6),e210054.
Supporting information
Additional supporting information may be found in theonline version of the article at the .
Cite this article
Elsabbagh, M., Yusuf, A., Zeidan, J., Scorah, J., Fombonne, E., Durkin, M.S., Saxena, S. and Shih, A. (2022), The time has come for living systematic reviews in autism research. Autism Research, 15: 1187-1188.

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