title: Sleep characteristics, chronotype and winter depression in 10-20-year-olds in northern European Russia.
abstract: The purpose of this work was to examine the relationships between geographical coordinates and the prevalence of winter depression (SADW ), and to compare the sleep characteristics and chronotype of youths with and without SADW . We conducted a cross-sectional study of self-reported sleep characteristics, chronotype and winter depression in northern European Russia. Two questionnaires, the Munich Chronotype Questionnaire (MCTQ) and the Seasonal Pattern Assessment Questionnaire (SPAQ), were administered to a total of 3435 adolescents aged 10-20 years (1517 males and 1918 females). The prevalence of SADW in the study population was 8.4% and sub-SADW 11.8%. Four variables predicted the likelihood of SADW in youths: sex [higher in females: odds ratio (OR): 1.87, P < 0.0001], age (increases with age: OR: 1.09, P < 0.001), latitude (higher in the North: OR: 1.49, P < 0.029) and position in the time zone (higher in the West: OR: 1.61, P < 0.001). Later sleeping and waking, longer sleep latencies, more severe sleep inertia, shorter total sleep times and lower sleep efficiencies were observed in both males and females with SADW . The influence of SADW on sleep characteristics was more pronounced on school days. Significant phase delays of the sleep-wake rhythm and severe social jetlag (the difference between the mid-point of sleep phase at weekends and on workdays) were observed in females with SADW , but not in males. There are significant differences in sleep characteristics and chronotype between people with SADW and no-SAD. We demonstrate that both latitude of residence and location within the time zone are significant predictors of SADW in young inhabitants of the North.
authors.affiliation: Institute of Physiology, Komi Science Centre, Ural Branch, Russian Academy of Science, Syktyvkar, Russia.
authors.forename: Mikhail F
authors.initials: MF
authors.lastname: Borisenkov
authors.affiliation: Syktyvkar State University, Syktyvkar, Russia.
authors.forename: Natalia B
authors.initials: NB
authors.lastname: Petrova
authors.affiliation: Syktyvkar State University, Syktyvkar, Russia.
authors.forename: Vladimir D
authors.initials: VD
authors.lastname: Timonin
authors.affiliation: Centre for Development of Education, Petrozavodsk, Russia.
authors.forename: Lyudmila I
authors.initials: LI
authors.lastname: Fradkova
authors.affiliation: Institute of Biology, Karelian Science Centre, Russian Academy of Sciences, Petrozavodsk, Russia.|Petrozavodsk State University, Petrozavodsk, Russia.
authors.forename: Sergey N
authors.initials: SN
authors.lastname: Kolomeichuk
authors.affiliation: Institute of the North Industrial Ecology Problem, Kola Science Centre, Russian Academy of Science, Apatity, Russia.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Kosova
authors.affiliation: Middle School No. 15, Apatity, Russia.
authors.forename: Olga N
authors.initials: ON
authors.lastname: Kasyanova
mesh_terms: D000293:Adolescent; D000375:Aging; D002648:Child; D002940:Circadian Rhythm / Q000502:physiology*; D003430:Cross-Sectional Studies; D003863:Depression / Q000453:epidemiology* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D012426:Russia / Q000453:epidemiology; D012621:Seasons; D057566:Self Report; D012727:Sex Characteristics; D012890:Sleep / Q000502:physiology*; D020178:Sleep Disorders, Circadian Rhythm / Q000453:epidemiology / Q000503:physiopathology; D012894:Sleep Stages / Q000502:physiology; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: seasonal affective disorder; sleep disturbances; sleep phase delay; social time; solar time; youths