Motor Performance in Autistic Youth From Childhood Through Adolescence: Evidence for Both Sustained and Widening Group Differences.

Although motor-skill differences in autistic individuals are well established, there is diverging evidence regarding what happens to motor skills in autistic children as they become adolescents. Using both cross-sectional and longitudinal data, we examined fine and gross motor skills and grip strength of 187 autistic participants and 136 non-autistic participants (i.e., with no known diagnoses), aged 6-18 years-old. Participants completed the Bruininks-Oseretsky Test of Motor Proficiency-Short Form, Second Edition (BOT-2 SF), and maximal grip strength testing. Linear mixed-effects regression analyses indicated motor-skill differences between autistic and non-autistic participants across this age range; however, the nature of these differences depended on the specific motor domain (i.e., strength) and measure. Specifically, grip strength and BOT-2 SF strength subtest scores showed widening group differences with increasing age, whereas overall BOT-2 SF scores and subtests showed sustained or narrowing group differences through adolescence. However, items on the BOT-2 SF also demonstrated substantial ceiling effects, which may obscure later group differences between autistic and non-autistic participants and highlight the need for measures that encompass a greater range of motor skills into adolescence. These findings have important implications for healthcare, education, and community supports that address age-related motor differences within the autistic population.