Косова, А. Л. Chronotype, sleep length, and school achievement of 11- to 23-year-old students in northern European Russia / Borisenkov M. F., Perminova E. V., Kosova A. L. // Chronobiol. Int. - 2010. - Vol. 27. - P. 1259-1270.

Chronobiol Int Downloaded from informahealthcare.com by 217.66.146.98 on 07/23/10 For personal use only. Chronobiology International, 27(6): 1259-1270, (2010) i n f o r m s Copyright © 2010 Informa Healthcare USA, Inc. healthcare ISSN 0742-0528 p rin t/1525-6073 online ------------------- DOI: 10.3109/07420528.2010.487624 CHRONOTYPE, SLEEP LENGTH, AND SCHOOL ACHIEVEMENT OF 11- TO 23-YEAR-OLD STUDENTS IN NORTHERN EUROPEAN RUSSIA Mikhail F. Borisenkov ,1 Elena V. Perminova ,2 and Anna L. Kosova 3 1Institute o f Physiology, Komi Science Centre, Ural Bran ch o f Russian Academy o f Science, Syktyvkar, Russia 2Polar Geophysical Institute, Kola SC o f Russian Academy o f Science, Apatity, Russia yInstitute o f Problems o f In dustrial Ecology o f the No rth, Kola SC o f Russian Academy o f Science, Apatity, Russia Residing at no rth ern latitudes for long periods o f time is associated with sleep dis­ turbances and internal desynchronization, which are considered to be causes of chronic diseases in old age. In children and teenagers, they result in a poor school achievement, psychological problems, and increase in consumption of stimulants. In this paper, we analyze the relationship between both chronotype and sleep length and the variables of age, sex, place of residence, type of settlement (village/city), lati­ tude and longitude of residence, and school achievement of young inhabitants of no rth ern European Russia. We surveyed 1101 children and teenagers between 11 to 23 yrs of age living in four settlements located between 59° and 67° North latitude and 33° and 60° East longitude. T he Munich chronotype questionnaire (MCTQ) was used in the study, and all participants were also required to answer a question about their school achievements. An analysis o f covariance (ANCOVA) was used to assess the influence o f the analyzed factors on sleep length and chronotype. Self-reported sleep length of teenagers depended moderately on age, whereas the place of resi­ dence, latitude, and type of settlement only had a weak effect. Chronotype strongly depended on place of residence and longitude; it moderately depended on latitude and age; and it weakly depended on sex and type of settlement. T he sleep length of village teenagers was 46 min longer than that of u rban teenagers. T he authors found a 1 h and 18 min phase delay o f the sleep-wake rhythm (as a marker o f chronotype) in teenagers moving in the East-West direction and a 16-min delay moving in the South-North direction within one time zone. There was a weak, bu t significant, posi­ tive correlation between chronotype and time of sunrise. There was about a 2-fold stronger influence of chronotype than sleep length on achievement of school children and college students. We conclude that socioeconomic factors exert a significant influ­ ence on sleep length and that climatic conditions exert a significant influence or Submitted December 10, 2009; Returned for revision January 18, 2010; Accepted April 5, 201C Address correspondence to Mikhail F. Borisenkov, PhD, Institute of Physiology Pervon 50, 167982 Syktyvkar, Russia. E-mail: borisenkov@physiol.komisc