Browsing by Subject "vuorokausirytmi"
Now showing items 1-13 of 13
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(2022)Aims of the study. The aim of this study was to examine normative development of sleep patterns and circadian rhythmicity during adolescence. Previous studies have found that sleep duration shortens across the lifespan, and especially adolescents’ sleep timing shifts later due to physiological and psychological factors. Sleep patterns in adolescence are connected to individual’s endogenous circadian rhythms, usually measured by delayed melatonin secretion in the evening. There is a lack of understanding how sleep patterns are related to circadian body temperature rhythms during adolescence. Methods. This study was part of SleepHelsinki! cohort study of the Sleep & Mind Research Group. Adolescents’ sleep patterns were measured with actigraphies, whereas circadian body temperature was measured from the skin surface. Circadian temperature rhythmicity was inspected by circadian period length, the mesor of skin surface temperature and the amplitude of daily changes within the rhythm. Baseline measurements were measured from 215 (71.6 % girls) adolescents aged 16–18 years. At one-year follow-up, 156 (76.3 % girls) adolescents were measured again. Mixed models for repeated measures were used to examine changes over the year in sleep patterns and endogenous circadian temperature rhythm, separately for both girls and boys. Sex differences were tested with one-way variance analysis. Linear and ordinal regressions were used to predict sleep and circadian rhythm over the year. Results and conclusions. Over the year, adolescents’ sleep duration became longer during the week, while weekend sleep shortened. However, this change was only significant for girls. Sleep schedule became more delayed for both girls and boys during the week, as sleep onset, midpoint and offset occurred at a later time. Circadian rhythm changed for boys, as their average skin surface temperature increased, and their circadian temperature amplitude became smaller. Boys also had significantly lower circadian temperature amplitude than girls at the follow-up. Compared to boys, girls were 5.85 times more likely to have a high circadian temperature amplitude at the follow-up measurement. Changes in sleep length during the week was moderated by temperature amplitude, with higher circadian amplitude predicting sleep duration to become longer. Still, the likelihood to have long sleep duration was affected by past sleep duration.
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(2022)Aims of the study. The aim of this study was to examine normative development of sleep patterns and circadian rhythmicity during adolescence. Previous studies have found that sleep duration shortens across the lifespan, and especially adolescents’ sleep timing shifts later due to physiological and psychological factors. Sleep patterns in adolescence are connected to individual’s endogenous circadian rhythms, usually measured by delayed melatonin secretion in the evening. There is a lack of understanding how sleep patterns are related to circadian body temperature rhythms during adolescence. Methods. This study was part of SleepHelsinki! cohort study of the Sleep & Mind Research Group. Adolescents’ sleep patterns were measured with actigraphies, whereas circadian body temperature was measured from the skin surface. Circadian temperature rhythmicity was inspected by circadian period length, the mesor of skin surface temperature and the amplitude of daily changes within the rhythm. Baseline measurements were measured from 215 (71.6 % girls) adolescents aged 16–18 years. At one-year follow-up, 156 (76.3 % girls) adolescents were measured again. Mixed models for repeated measures were used to examine changes over the year in sleep patterns and endogenous circadian temperature rhythm, separately for both girls and boys. Sex differences were tested with one-way variance analysis. Linear and ordinal regressions were used to predict sleep and circadian rhythm over the year. Results and conclusions. Over the year, adolescents’ sleep duration became longer during the week, while weekend sleep shortened. However, this change was only significant for girls. Sleep schedule became more delayed for both girls and boys during the week, as sleep onset, midpoint and offset occurred at a later time. Circadian rhythm changed for boys, as their average skin surface temperature increased, and their circadian temperature amplitude became smaller. Boys also had significantly lower circadian temperature amplitude than girls at the follow-up. Compared to boys, girls were 5.85 times more likely to have a high circadian temperature amplitude at the follow-up measurement. Changes in sleep length during the week was moderated by temperature amplitude, with higher circadian amplitude predicting sleep duration to become longer. Still, the likelihood to have long sleep duration was affected by past sleep duration.
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(2015)Introduction: Individuals differ by their circadian rhythms from extreme morning types to extreme evening types, referred to as chronotypes. Evening types tend to consume unhealthier foods and nutrients which may predispose them at higher risk of obesity as compared to the morning types. Recently it has been suggested that food timing may play a role in weight regulation. However, the association between chronotype, food timing and obesity is not well known. Study aims: The aim of this study was to describe energy and macronutrient intake timing by chronotypes, especially the intakes by 10 a.m. and after 8 p.m. and the differences between weekdays and weekends. In addition the association between energy intake timing and obesity was investigated. Materials and methods: The study population included 847 subjects aged 25-74 years from the National FINRISK 2007 and FINDIET 2007 studies. Of the participants 293 were evening, 308 intermediate and 248 morning types, based on validated Morningness-Eveningness Questionnaire. Diet was assessed using 48-hour recalls and 3-day food logs. Statistical analyses were conducted using general linear model, logistic regression and Mann-Whitney’s U-test. Analyses were adjusted for age, sex, education, smoking, leisure-time physical activity and sleep duration. Results: Evening types had later energy and macronutrient intake timing than the morning types. Evening types had 400 kJ lower total energy intake by 10 a.m. and 500 kJ higher total energy intake after 8 p.m. as compared to the morning types (p<0.001). Significant differences in macronutrient intake timing was found at the weekend. By 10 a.m. evening types had less sugar, fiber, fat, saturated fat and protein than the morning types (p<0.05). After 8 p.m evening types had more carbohydrates, sugar and fiber than the morning types (p<0.05). Higher energy intake after 8 p.m. was associated with obesity in the evening types but not in the morning types. The evening types who had more than 16% of their daily energy intake after 8 p.m. were twice as likely to be obese as compared to those evening types who had less than 16% of their daily energy intake after 8 p.m. (odds ratio 2.13, 95% CI 1.09 to 4.17). Conclusions: Chronotype was associated with food timing. Evening types had later energy and macronutrient intake timing than the morning types. By 10 a.m. and after 8 p.m. most significant differences were found in energy intake. Macronutrient intake timing differed at the weekend. Higher energy intake after 8 p.m. was associated with obesity in the evening types. Higher energy intake after 8 p.m. may put especially the evening types at higher risk of obesity. However, the cross-sectional design cannot reveal causality and therefore this hypothesis require further studying.
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(University of HelsinkiHelsingin yliopistoHelsingfors universitet, 1997)Oheisessa tutkimuksessa on tutkittu naalien vuorokausirytmiä ja vanhempainkäyttäytymistä seminaturaalissa ympäristössä. Tutkimus suoritettiin Tukholman yliopiston eläintieteellisellä tutkimusasemalla Tovetorpissa 12.5. - 24.6. 1993. Tutkimusta jatkettiin seuraavana kesänä. Tutkimus on osa professori Per Jensenin ja etologi Kerstin Malmin tekemää koiraeläinten käyttäytymistutkimusta. Naalien käyttäytymistä havainnoitiin vuorokauden jokaisena tuntina. Kiinnostuksen kohteena olevat käyttäytymismallit listattiin tutkimuspöytäkirjaan. Tutkimuspöytäkirjaan kootut havainnot analysoitiin Statview SE + Graphics (1987) Macintoshilla.
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(2020)Objectives. Over the last few decades, the usage of various digital devices has increased significantly. As people spend time on digital media especially in the evenings before bedtime, there has been a growing interest in researching the potential effects of digital media usage on sleep. The association between digital media usage and negative sleep outcomes can be explained by three different mechanisms: circadian effects of exposure to light from screens, stimulation from media content, and displacement of time spent sleeping by time spent using devices. The objective of this thesis was to review recent randomized controlled experiments regarding the effects of pre-sleep digital media usage on sleep and compare their study designs and results. Methods. Experimental studies were searched on PubMed and Ovid Mediline databases using the terms digital media, electronic media, screen light, blue light and sleep. Seven randomized controlled experiments published within the last five years were selected. All the studies had controlled the use of digital media and used both subjective and objective sleep measures. Results and conclusions. Most of the studies indicated that the pre-sleep usage of digital media has a negative effect on sleep. There were associations between the usage of digital media and sleep architecture, sleep onset latency, suppression of melatonin secretion and subjective sleepiness. In addition, each of the three mechanisms were supported by the studies. However, there were notable differences in the study designs between the studies, which made it difficult to assess the significance of the individual factors. There is a need for laboratory experiments with larger sample sizes as well as real-life studies to increase ecological validity. This would help specify recommendations regarding the use of digital media in order to improve human health and wellbeing.
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(University of HelsinkiHelsingin yliopistoHelsingfors universitet, 2012)Puunpurenta, jota kutsutaan myös ilmannielemiseksi, tarkoittaa hevosen toistuvaa, tarkoituksettomalta näyttävää eli stereotyyppistä käyttäytymistä, jossa hevonen tyypillisesti painaa etuhampaansa kiinteää pintaa vasten, vetää ilmaa ruokatorven alkuosaan päästäen nielusta korahtavan äänen. Puunpurentaa esiintyy noin 4-5 %:lla hevosista. Puunpurennan taustalla on todennäköisesti useita syitä geneettisistä tekijöistä, talliolosuhteisiin, ruokintaan, vieroitukseen ja muihin elinympäristön stressitekijöihin. Vielä ei tiedetä, miksi hevonen puree puuta. Puunpurennan tai erityisesti puunpurennan estämisen on havaittu muuttavan veren stressihormonipitoisuuksia ja puunpurijoilla on todettu muuttuneet dopamiinireseptoritiheydet tietyillä aivoalueilla. Nämä herkistyneet keskushermoston dopaminergiset radat voivat olla stereotyyppisen käytöksen yhteydessä seurausta pitkään jatkuneesta stressistä yhdistettynä geneettiseen alttiuteen. Tämän tutkielman kokeellinen osuus toimi pilottitutkimuksena laajemmalle hevosen stereotyyppisen käytöksen tutkimukselle. Tutkimuksessa videoitiin ja analysoitiin kolmen puutapurevan hevosen ja kolmen verrokkihevosen käytöstä karsinassa vietettynä aikana. Hevosia kuvattiin niiden omassa karsinassaan kaksi vuorokautta ja toisena vuorokautena niillä oli sydämen sykettä rekisteröivä EKG-laite selässään tutkimuksen toista osaa varten. Käytöksen analysointi toteutettiin luomalla käyttäytymiskoodit, joihin hevosten ilmentämät käyttäytymiset luokiteltiin ja mitattiin, kuinka paljon aikaa hevoset käyttivät kuhunkin toimintaan. Tavoitteena oli selvittää, mitä nauhoitteista pystyy näkemään ja analysoimaan ja onko käyttäytymiskoodit järkevästi luokiteltu, jotta varsinaisessa tutkimuksessa voidaan paremmin tutkia päivärytmin muutoksia. Tarkastelin myös, eroaako puunpurijahevosen käyttäytyminen ei-stereotyyppisesti käyttäytyvän verrokkihevosen käyttäytymisestä ja selvitin, häiritseekö EKG-laite hevosta. Tutkimuksessa yritettiin saada selville, minkä päivittäisen toiminnan kustannuksella puunpurijahevonen käyttää aikaa puunpurentaan ja eroavatko puunpurijahevosten ja verrokkihevosten päivärytmit toisistaan. Pilottitutkimuksessa tuli ilmi hevosten valintaan, kuvausteknisiin asioihin, koodien määrittelyyn ja tulosten esittämismuotoon liittyviä seikkoja, joita kannattaa ottaa huomioon varsinaista tutkimusaineistoa käsiteltäessä. Vielä ei havaittu viitteitä siitä, että puunpurijoiden ja verrokkien päivärytmissä olisi eroja eikä EKG-laite ei vaikuttanut hevosten käyttäytymiseen. Vain kaksi kolmesta puuta purevasta hevosesta esitti stereotyyppistä käytöstä seurantajakson aikana ja lisäksi tutkimuksen puunpurijat ilmensivät stereotyyppistä käytöstä vähän, arvioiden korkeintaan 0,5 % vuorokaudesta. Puunpurennalla ja ruokinta-ajoilla näytti olevan yhteys, kun taas kahden hevosen tavassa ilmentää stereotyyppistä käytöstä havaittiin ero; toinen näytti purevan puuta harvemmin ja pidempään, 10–30 kertaa kerralla, ja toinen puri puuta useammin, mutta alle kymmenen kerran sarjoja. Tällaista ei ole kuvattu kirjallisuudessa aiemmin.
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(University of HelsinkiHelsingin yliopistoHelsingfors universitet, 2005)2,3,7,8-Tetraklooridibentso-p-dioksiini (TCDD) kuuluu halogenoituihin aromaattisiin hiilivetyihin ja on ryhmän voimakkain myrkky. TCDD on ympäristömyrkky, joka rikastuu ravintoketjussa. Ihmiset altistuvat TCDD:lle kroonisesti ruoka-aineiden, Suomessa lähinnä kalan, välityksellä. TCDD:lla on useita akuutteja ja kroonisia toksisia vaikutuksia ihmisiin ja eläimiin. Pitkäaikaisen TCDD-altistuksen tärkeimpiä vaikutuksia ovat mm. kehityshäiriöt ja karsinogeenisuus. Akuutteja vaikutuksia ovat mm. näivetysoireyhtymä, immunosuppressio ja kuolema. TCDD:n myrkyllisyyden mekanismi tunnetaan vain osittain. Rotan käyttäytyminen ja elintoiminnot seuraavat vuorokausirytmiä. Rytmin päätahdistaja sijaitsee hypotalamuksessa ja rytmiin vaikuttavat sekä sisäiset että ulkoiset tekijät. Ulkoisista tekijöistä parhaiten tunnettuja ovat valo ja ravinnonsaanti. TCDD:n tiedetään vaikuttavan rottien syömiskäyttäytymiseen siten, että rehunkulutus vähenee, mistä seuraa näivetysoireyhtymä. Muista TCDD:n käyttäytymisvaikutuksista rotalla on vain vähän julkaistua tutkimustietoa. Tässä tutkimuksessa selvitettiin TCDD:n vaikutuksia Long-Evans (Turku A/B) -urosrottien käyttäytymiseen videovalvontaa käyttäen. Tutkimuksessa käytettiin kymmentä Long-Evans -kannan urosrottaa, joista viisi altistettiin TCDD:lle annoksella 100 µg/kg. Rotat sijoitettiin yksittäin käyttäytymistutkimukseen suunniteltuihin häkkeihin, joissa niitä videokuvattiin kaksi päivää ennen altistusta ja viisi päivää altistuksen jälkeen. Rotat olivat vapaalla ruokinnalla. Tähän tutkimukseen valittiin analysoitaviksi päivä ennen altistusta sekä toinen ja viides päivä altistuksen jälkeen. Valittuina päivinä rottia tarkkailtiin 24 tuntia. Käyttäytyminen jaettiin neljään eri kategoriaan, jotka ovat Lepää, Syö, Pesee ja Liikkuu. TCDD:lle altistettujen rottien automaattilaitteistolla mitattu rehunkulutus väheni kokeen aikana tilastollisesti merkitsevästi toisesta koepäivästä alkaen, mutta juomisessa ei todettu muutoksia. Käyttäytymisen seurannan perusteella syömiseen käytetty kokonaisaika ei eronnut TCDD- ja kontrolliryhmän välillä, mutta hajonta TCDD-ryhmän sisällä kasvoi. TCDD:lle altistettujen rottien turkin puhdistamiseen kulunut kokonaisaika ja puhdistamiskertojen lukumäärä vähenivät koepäivinä kaksi ja viisi. Ero kontrollirottiin on tilastollisesti merkitsevä. Vuorokausirytmissä ei havaittu merkittäviä muutoksia TCDD-altistuksen jälkeen. Rehunkulutuksen vähentyminen oli odotettu TCDD:n vaikutus. Yllättävää oli, ettei syömiseen käytetyssä kokonaisajassa tai syömiskerran keskimääräisessä kestossa altistuksen jälkeen havaittu johdonmukaista merkitsevää muutosta. Tämä voisi viitata rottien syömistehokkuuden vähentymiseen. Lisääntynyt hajonta TCDD-ryhmän sisällä syömiseen kulutetussa ajassa viitannee TCDD:n vaikuttavan yksilöllisesti käyttäytymiseen. Turkin puhdistamisen vähentyminen voi liittyä vähentyneeseen rehunkulutukseen. Letaali TCDD-annos muuttaa viiden vuorokauden kuluessa L-E-rottien ulkoista käyttäytymistä ja vuorokausirytmiä laboratorio-olosuhteissa melko vähän.
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(University of HelsinkiHelsingin yliopistoHelsingfors universitet, 1999)Tutkimuksen tavoitteena oli selvittää sian kausilisääntymisen endokrinologista perustaa. Haluttiin nähdä villi- ja kesysian erot ja yhtäläisyydet niiden melatoniinin erityksessä ja vuorokauden- ja vuodenaikaan sidotuissa rytmeissä. Kausilisääntymisen syiden ymmärtämisellä pyritään syyshedelmättömyysongelman parempaan hallintaa. Tutkimus toteutettiin neljänä erinäyttenottokertana: keväällä, kesällä, syksyllä ja talvella. Yhteensa 20 kesysiasta ja 20 villisiasta otettiin 48 tunnin ajan verinäyteitä kahden tunnin välein. Siat pidettiin luonnon valaistuksessa näytteenoton ajan. Näytteistä määritettiin melatoniini Buhlman melatoniini-RIA-menetelmällä. Tuloksissa villi- ja kesysiolla melatoniinin erityksessä ei ollut eroa. Erot olivat suuremmat yksilöiden kuin rotujen välillä. Molemmilla roduilla näkyy selkeä vuorokaudenaikainen melatoniinirytmi. Melatoniinipitoisuus nousee pimeänä aikana ja on perustasolla valoisana aikana. Toisin kuin aiemmin on oletettu sika näyttäisi melatoniinin suhteen käyttäytyvän samoin kuin selkeä lyhyen päivän kausilisääntyjä lammas. Niinpä sikataloudelle ongelmallinen kausilisääntyminen on sialle fysiologista. Yksilöiden välisestä vaihtelusta johtuen on mahdollista, että tietyt yksilöt ovat herkempiä kausilisääntymiselle, jolloin ympäristön merkitys ongelman esilletulossa korostuu.
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(2013)The bioluminescent and toxin-producing dinoflagellate Alexandrium ostenfeldii forms dense blooms in coastal areas of the Baltic Sea. Bioluminescence, light production by an organism through a chemical reaction, is a nocturnal, rhythmic phenomenon in surface algae. In this study, the bioluminescence pattern and rhythm of A. ostenfeldii was under investigation. Procedures for continuous bioluminescence measurements, to support dedicated environmental monitoring of toxic dinoflagellate blooms, were developed. The study consisted mainly of laboratory experiments. Semi-continuous field measurements were included for comparison. In the laboratory, the light production of monocultures of A. ostenfeldii was measured with a spectroluminometer or bathyphotometer, continuously during the night, or for several consecutive days. The method to stimulate bioluminescence was varied, as well as the recovery period of the cells after stimulation. Light regimes during growth and pre-measurement adaptation were also taken into account. The experiments confirm that bioluminescence in A. ostenfeldii follows a circadian pattern and can be stimulated with the chosen methods. Bioluminescence could also be stimulated after culturing in continuous light. Measurement parameters for rhythm experiments (stimulation frequency and recovery period), were optimised. Multi-day experiments in complete darkness suggested that sufficient energy was available to maintain bioluminescent response during one night, although an endogenous rhythm remained present. These experiments gave insight to the phenomenon of bioluminescence regulation in A. ostenfeldii, but also gave rise to new questions. Some repeated measurements resulted in very low bioluminescence intensity, without an obvious reason. The light regime is not the only factor controlling bioluminescence. The interplay between bioluminescence and the growth and condition of the cultures is of interest.
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(2019)Aims. Sleep is very important for brain maturation in adolescence. However, the youth doesn’t often sleep enough. In adolescence evening preference in circadian rhythm becomes more common. This evening-type chronotype is often inconsistent with environment, such as early school mornings. In the long run this can lead into sleep deprivation which can then lead into low vitality, deficits in attention sustaining or some health problems for example. Also, evening-chronotype is associated with lower vitality, depressive and anxiety symptoms or health issues in adolescence. In adolescence it is also common to have unsteadiness of emotions. The aim of this study is to examine the associations between circadian rhythm and chronotype, vitality and emotions in adolescence. Additionally, the differences between genders in chronotype are also examined. Methods. 329 16–19-years old adolescents (69.9% girls) participated in the study for a week. The data used was from a Finnish cohort study SleepHelsinki!. The circadian rhythm and chronotype were assessed with actigraphy. Vitality and emotions were assessed three times in a day with a mobile application PsyMate™ which is based on Experience Sampling Method. The associations were examined with linear mixed models. Results and conclusions. In adolescence the circadian rhythm of girls is on average earlier than boys. Daytime low vitality is associated with less positive and more negative emotions in the same day. The association between low vitality and less positive emotions gets more intense as the study goes further. Chronotype as a continuous variable is not associated with daytime emotions or vitality in adolescence. Chronotype that is divided into three same sized groups is associated with daytime vitality as earlier chronotype is associated with lower daytime vitality. In adolescence the association between vitality and emotions should be paid attention to more, because vitality is something you might influence on with enough sleep. Guaranteeing higher vitality can also in the long run prevent mental health disorders since higher vitality could help stabilize emotions.
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(2019)Aims. Sleep is very important for brain maturation in adolescence. However, the youth doesn’t often sleep enough. In adolescence evening preference in circadian rhythm becomes more common. This evening-type chronotype is often inconsistent with environment, such as early school mornings. In the long run this can lead into sleep deprivation which can then lead into low vitality, deficits in attention sustaining or some health problems for example. Also, evening-chronotype is associated with lower vitality, depressive and anxiety symptoms or health issues in adolescence. In adolescence it is also common to have unsteadiness of emotions. The aim of this study is to examine the associations between circadian rhythm and chronotype, vitality and emotions in adolescence. Additionally, the differences between genders in chronotype are also examined. Methods. 329 16–19-years old adolescents (69.9% girls) participated in the study for a week. The data used was from a Finnish cohort study SleepHelsinki!. The circadian rhythm and chronotype were assessed with actigraphy. Vitality and emotions were assessed three times in a day with a mobile application PsyMate™ which is based on Experience Sampling Method. The associations were examined with linear mixed models. Results and conclusions. In adolescence the circadian rhythm of girls is on average earlier than boys. Daytime low vitality is associated with less positive and more negative emotions in the same day. The association between low vitality and less positive emotions gets more intense as the study goes further. Chronotype as a continuous variable is not associated with daytime emotions or vitality in adolescence. Chronotype that is divided into three same sized groups is associated with daytime vitality as earlier chronotype is associated with lower daytime vitality. In adolescence the association between vitality and emotions should be paid attention to more, because vitality is something you might influence on with enough sleep. Guaranteeing higher vitality can also in the long run prevent mental health disorders since higher vitality could help stabilize emotions.
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(2021)Objective. Despite the health benefits of physical exercise, several adolescents exercise less than recommended and physical activity decreases from childhood to adolescence. However, there has been quite little research into the factors affecting physical activity. The circadian rhythm shifts later in adolescence, which is linked to problems with schooling, as well as psychological and physical difficulties. However, further objective research is needed of the association of circadian rhythm and physical activity in adolescence. This study examined the association of circadian period length and timing of the circadian rhythm to physical activity in adolescents and whether sex moderates these associations. Methods. The sample consisted of 262 16–19 years old adolescents (70.6 % girls) who participated in the cohort study SleepHelsinki!. Circadian period length was measured by skin temperature and timing of the circadian rhythm was measured with an actigraphs according to the midpoint of sleep, as well as with the reduced version of the MEQ survey, which measures circadian preference. Metabolic equivalents as well as the amount of sedentary behavior, light physical activity and moderate to vigorous physical activity was calculated from the actigraphy data. Relationship between circadian period length and physical activity was analyzed with linear and quadratic regression analyzes, and relationship between midpoint of sleep and physical activity with linear regression analyzes. Relationship between circadian preference and physical activity was analyzed by one-way analyzes of variance. The moderating effect of gender was examined by adding the interaction of gender and independent variable to the models. Results. Circadian period length was in a quadratic relationship to light as well as moderate to vigorous physical activity: shorter and longer than average circadian period associated with lower activity level and a near-average circadian period with higher activity level. Later sleep midpoint associated with lower metabolic equivalent, lower light and moderate to vigorous physical activity and higher sedentary time. Circadian preference was not associated with physical activity. Gender did not moderate associations. Conclusions. Adolescents whose circadian rhythm is delayed or inconsistent with the rhythm of society should be considered when planning ways to support adolescent’s physical activity, because these adolescents are at greater risk for physical inactivity and its adverse health effects. One way could be shifting school start times later, which would reduce adolescent’s social jet lag, sleep deprivation and daytime fatigue, and thus support their physical activity.
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(2021)Objective. Despite the health benefits of physical exercise, several adolescents exercise less than recommended and physical activity decreases from childhood to adolescence. However, there has been quite little research into the factors affecting physical activity. The circadian rhythm shifts later in adolescence, which is linked to problems with schooling, as well as psychological and physical difficulties. However, further objective research is needed of the association of circadian rhythm and physical activity in adolescence. This study examined the association of circadian period length and timing of the circadian rhythm to physical activity in adolescents and whether sex moderates these associations. Methods. The sample consisted of 262 16–19 years old adolescents (70.6 % girls) who participated in the cohort study SleepHelsinki!. Circadian period length was measured by skin temperature and timing of the circadian rhythm was measured with an actigraphs according to the midpoint of sleep, as well as with the reduced version of the MEQ survey, which measures circadian preference. Metabolic equivalents as well as the amount of sedentary behavior, light physical activity and moderate to vigorous physical activity was calculated from the actigraphy data. Relationship between circadian period length and physical activity was analyzed with linear and quadratic regression analyzes, and relationship between midpoint of sleep and physical activity with linear regression analyzes. Relationship between circadian preference and physical activity was analyzed by one-way analyzes of variance. The moderating effect of gender was examined by adding the interaction of gender and independent variable to the models. Results. Circadian period length was in a quadratic relationship to light as well as moderate to vigorous physical activity: shorter and longer than average circadian period associated with lower activity level and a near-average circadian period with higher activity level. Later sleep midpoint associated with lower metabolic equivalent, lower light and moderate to vigorous physical activity and higher sedentary time. Circadian preference was not associated with physical activity. Gender did not moderate associations. Conclusions. Adolescents whose circadian rhythm is delayed or inconsistent with the rhythm of society should be considered when planning ways to support adolescent’s physical activity, because these adolescents are at greater risk for physical inactivity and its adverse health effects. One way could be shifting school start times later, which would reduce adolescent’s social jet lag, sleep deprivation and daytime fatigue, and thus support their physical activity.
Now showing items 1-13 of 13