Have infant gross motor abilities changed in 20 years? A re-evaluation of the Alberta Infant Motor Scale normative values

AIM To compare the original normative data of the Alberta Infant Motor Scale (AIMS) (n=2202) collected 20 years ago with a contemporary sample of Canadian infants. METHOD This was a cross-sectional cohort study of 650 Canadian infants (338 males, 312 females; mean age 30.9 wks [SD 15.5], range 2 wks-18 mo) assessed once on the AIMS. Assessments were stratified by age, and infants proportionally represented the ethnic diversity of Canada. Logistic regression was used to place AIMS items on an age scale representing the age at which 50% of the infants passed an item on the contemporary data set and the original data set. Forty-three items met the criterion for stable regression results in both data sets. RESULTS The correlation coefficient between the age locations of items on the original and contemporary data sets was 0.99. The mean age difference between item locations was 0.7 weeks. Age values from the original data set when converted to the contemporary scale differed by less than 1 week. INTERPRETATION The sequence and age at emergence of AIMS items has remained similar over 20 years and current normative values remain valid. Concern that the 'back to sleep' campaign has influenced the age at emergence of gross motor abilities is not supported.