title: Effect of birth season on circadian typology appearing in Japanese young children aged 2 to 12 years disappears in older students aged 18 to 25 years.
abstract: Several studies suggest that season of birth differentially affects the physiological characteristics of humans. Those living at relatively high latitude, such as Canada, Spain, and Italy (44°N-45°N), and born in the fall tended to be "morning-type" persons in comparison to those born in other seasons. There are relatively little data on the affect of season of birth on people residing at low latitude. Here the authors show that at low latitude, Kochi, Japan (33°N), the effect of season of birth on the morningness chronotype is confined to young children aged 1-12 yrs, disappearing in elderly persons. Only female participants aged 2-12 yrs born in the fall, especially in November, were significantly morning-typed (p < .001) in comparison to those born in the other seasons, whereas there were no such significant season-of-birth differences in morningness-eveningness preference among male participants. Moreover, both female and male participants aged 13-25 yrs showed no significant seasonal differences in morningness-eveningness preference. The small effects detected in this study might be due to smaller seasonal change in day length at the relatively lower latitude of Kochi.
authors.affiliation: Laboratory of Environmental Physiology, Faculty of Education, Kochi University, Kochi, Japan. haratets@kochi-u.ac.jp
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Harada
authors.forename: Ryo
authors.initials: R
authors.lastname: Kobayashi
authors.forename: Kai
authors.initials: K
authors.lastname: Wada
authors.forename: Risa
authors.initials: R
authors.lastname: Nishihara
authors.forename: Aska
authors.initials: A
authors.lastname: Kondo
authors.forename: Osami
authors.initials: O
authors.lastname: Akimitsu
authors.forename: Teruki
authors.initials: T
authors.lastname: Noji
authors.forename: Nozomi
authors.initials: N
authors.lastname: Taniwaki
authors.forename: Miyo
authors.initials: M
authors.lastname: Nakade
authors.forename: Milada
authors.initials: M
authors.lastname: Krejci
authors.forename: Hitomi
authors.initials: H
authors.lastname: Takeuchi
mesh_terms: D000293:Adolescent; D000328:Adult; D044466:Asian People; D002648:Child; D002675:Child, Preschool; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D036801:Parturition / Q000502:physiology*; D012621:Seasons; D013334:Students; D011795:Surveys and Questionnaires; D055815:Young Adult