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Low Cardiorespiratory Fitness as a Novel Risk Factor for ADHD in Childhood and Adolescence: A 6-Year Cohort Study Also Exploring the Role of Overweight and Obesity
33 Pages Posted: 10 Apr 2020
More...Abstract
Background: The present work examines (1) whether overweight/obesity and low CRF are associated with increased ADHD symptoms in childhood (cross-sectional analysis), and (2) whether overweight/obesity and low CRF levels during childhood predict increased ADHD symptoms in adolescence (longitudinal analysis).
Methods: Data were examined from a longitudinal study of Estonian inhabitants who took part in the European Youth Heart Study (EYHS) in 1998 and 1999 (baseline age 9 years), who were re-evaluated 6 years later as part of the longitudinal Estonian Children Personality Behaviour and Health Study (ECPBHS). CRF was determined via an incremental maximal cycle-ergometer test, overweight/obesity was based on BMI, and the 7-point af Klinteberg Hyperactivity Scale was used to assess ADHD symptoms at both time points.
Findings: In the cross-sectional analysis, children with overweight/obesity were at greater risk of increased ADHD symptoms compared to underweight/normal-weight children, as were those with low CRF compared to fit children (OR=1.92 and 95%CI=1.02–3.55, and OR=1.84 and 95%CI=1.13–2.98, respectively). The cross-sectional association between BMI and ADHD symptoms was mediated by CRF (z=2.116, 42.9%; p =0.034). The longitudinal analysis showed low CRF in childhood to be associated with a greater risk of increased ADHD symptoms 6 years later in adolescence (OR=2.26 and 95%CI=1.14–4.47), even after adjusting for baseline ADHD symptoms and BMI.
Interpretation: Our result suggests that being unfit is an additional risk factor for increased ADHD symptoms during childhood and adolescence. The association between BMI and ADHD symptoms was mediated by CRF in the cross-sectional analysis; no association was seen between overweight/obesity and increased ADHD symptoms in the longitudinal analysis.
Funding Statement: This study was mainly funded with the support of the Estonian Research Council grants IUT20-40 and IUT42-2. The study was further supported with funds from the European Union Horizon 2020 research and innovation program under grant agreement No 667302. The study was also partially funded by the University of Granada, Research and Knowledge Transfer Fund (PPIT) 2016, the Excellence Actions Programme: Units of Scientific Excellence; Scientific Unit of Excellence on Exercise and Health (UCEES), the Andalusian Regional Government, the Regional Ministry of Economy, Knowledge, Entreprises and University, and the European Regional Development Fund (ERDF), ref. SOMM17/6107/UGR. In addition, this study was further supported by the SAMID III network, RETICS, funded by the PN IþDþI 2017–2021 (Spain). The study was additionally supported by the MINECO/FEDER (DEP2013-47540, DEP2016-79512-R)
Declaration of Interests: None.
Ethics Approval Statement: The study was approved by the Tartu University Ethics Review Committee on Human Research (no. 49/30-199). All subjects and their parents gave written informed consent to be included.
Keywords: ADHD; cardiorespiratory fitness; youth; obesity; longitudinal study
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