title: Seasonal variations of neuromotor development by 14 months of age: Hamamatsu Birth Cohort for mothers and children (HBC Study).
abstract: The present study aimed at investigating whether neuromotor development, from birth to 14 months of age, shows seasonal, cyclic patterns in association with months of birth. Study participants were 742 infants enrolled in the Hamamatsu Birth Cohort (HBC) Study and followed-up from birth to the 14th month of age. Gross motor skills were assessed at the ages of 6, 10, and 14 months, using Mullen Scales of Early Learning. The score at each assessment was regressed onto a trigonometric function of months of birth, with an adjustment for potential confounders. Gross motor scores at the 6th and 10th months showed significant 1-year-cycle variations, peaking among March- and April-born infants, and among February-born infants, respectively. Changes in gross motor scores between the 10th and 14th months also showed a cyclic variation, peaking among July- and August-born infants. Due to this complementary effect, gross motor scores at the 14th month did not show seasonality. Neuromotor development showed cyclic seasonality during the first year of life. The effects brought about by month of birth disappeared around 1 year of age, and warmer months seemed to accelerate the neuromotor development.
authors.affiliation: Research Center for Child Mental Development, Hamamatsu University School of Medicine, Hamamatsu, Japan. tsuchiya@hama-med.ac.jp
authors.forename: Kenji J
authors.initials: KJ
authors.lastname: Tsuchiya
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tsutsumi
authors.forename: Kaori
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Nori
authors.initials: N
authors.lastname: Takei
authors.forename: Makiko
authors.initials: M
authors.lastname: Narumiya
authors.forename: Maiko
authors.initials: M
authors.lastname: Honda
authors.forename: Ismail
authors.initials: I
authors.lastname: Thanseem
authors.forename: Ayyappan
authors.initials: A
authors.lastname: Anitha
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Suzuki
authors.forename: Hideo
authors.initials: H
authors.lastname: Matsuzaki
authors.forename: Yasuhide
authors.initials: Y
authors.lastname: Iwata
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nakamura
authors.forename: Norio
authors.initials: N
authors.lastname: Mori
mesh_terms: D002657:Child Development / Q000502:physiology*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007564:Japan; D008297:Male; D009034:Mother-Child Relations; D009048:Motor Skills; D011597:Psychomotor Performance; D012621:Seasons; D013997:Time Factors