PHOTOPERIOD AT BIRTH DOES NOT MODULATE THE DIURNAL PREFERENCE IN ASIAN POPULATION

Abstract

Two research groups reported that diurnal preference in Canadian and South European populations was modulated by the season of birth. The aim of the present study was to examine this association in the Japanese population. In this study, 1156 college students were administered the Morningness-Eveningness Questionnaire and asked the date and place of birth. Our results demonstrated that neither photoperiod nor season of birth modulated diurnal preference in the Japanese population. Two biological differences are reported to exist between Caucasians and Asians: polymorphisms of circadian clock genes and difference in ocular photosensitivity. These ethnic differences might characterize the circadian photosensitivity in infancy. (Author correspondence: [email protected]).

Key Words:

• Human circadian rhythms
• Diurnal preference
• Photoperiod
• Ethnicity

ACKNOWLEDGMENTS

The authors would like to acknowledge the excellent secretarial work by Ms. Fusako Takao. This study was supported financially by the Grants-in-Aid #21590262 and #60225399 from The Japan Society for the Promotion of Science (M.T.), as well as the Special Grant for Young Researchers from Tokai University (M.T.).