Intellectual disability in the children of the Avon Longitudinal Study of Parents and Children (ALSPAC)

Paul C Madley-Dowd*, Richard G Thomas, Andrew W Boyd, Stanley Zammit, Jon E Heron, Dheeraj Rai

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Background: Intellectual disability (ID) describes a neurodevelopmental condition involving impaired cognitive and functional ability. Here, we describe a multisource variable of ID using data from the Avon Longitudinal Study of Parents and Children (ALSPAC).
Methods: The multisource indicator variable for ID was derived from i) IQ scores less than 70 measured at age 8 and at age 15, ii) free text fields from parent reported questionnaires, iii) school reported provision of educational services for individuals with a statement of special educational needs for cognitive impairments, iv) from relevant read codes contained in GP records, iv) international classification of disease diagnoses contained in electronic hospital records and hospital episode statistics and v) recorded interactions with mental health services for ID contained within the mental health services data set. A case of ID was identified if two or more sources indicated ID. A second indicator, labelled as “probable ID”, was created by relaxing the cut off in IQ scores to be less than 85. An indicator variable for known causes of ID was also created to aid in aetiological studies where ID with a known cause may need to be excluded.
Results: 158 of 14,370 participants (1.10%) were indicated as having ID by two or more sources and 449 (3.12%) were indicated as having probable ID when the criteria for IQ scores was relaxed to less than 85. There were 476 participants (3.31%) with 1 or fewer sources of available information on ID; these participants had their multisource variable set to missing. The number of cases of ID with known cause was 31 (0.22% of the cohort, 19.6% of those with ID).
Conclusions: The multisource variable of ID can be used in future analyses on ID in ALSPAC children.
Original languageEnglish
Article number172
JournalWellcome Open Research
Publication statusPublished - 11 Jan 2023

Bibliographical note

Funding Information:
The UK Medical Research Council and Wellcome (Grant ref: 217065/Z/19/Z) and the University of Bristol provide core support for ALSPAC. This publication is the work of the authors and PMD, SZ, JH, AB, RT and DR will serve as guarantors for the contents of this paper. For the purpose of Open Access, the author has applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission. A comprehensive list of grants funding is available on the ALSPAC website (; This research was specifically funded by the Wellcome Trust and MRC (Grant refs: 076467/Z/05/Z; 203776/Z/16/A; 092731; 086118; MC_PC_17210). This research was also supported by the National Institute for Health Research (NIHR) Biomedical Research Centre at University Hospitals Bristol and Weston NHS Foundation Trust and the University of Bristol (Grant ref: BRC-1215-2011). The funders had no role in the design of the study, data management, data analysis, interpretation of findings and the decision to submit the article for publication.

Publisher Copyright:
Copyright: © 2023 Madley-Dowd P et al.

Structured keywords

  • Bristol Population Health Science Institute


  • intellectual disability
  • Neurodevelopment
  • Record linkage


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