Chronotype, gender and general health

References

• Adan A, Natale V. (2002). Gender differences in morningness-eveningness preference. Chronobiol Int. 19:709–20.
   PubMed Web of Science ®Google Scholar
• Aledavood T, López E, Roberts SG, et al. (2015). Daily rhythms in mobile telephone communication. PLoS One. 10:e0138098.
   PubMed Web of Science ®Google Scholar
• Alibhai FJ, Tsimakouridze EV, Reitz CJ, Pyle WG, Martino TA. (2015). Consequences of circadian and sleep disturbances for the cardiovascular system. Can J Cardiol. 31:860–72.
   PubMed Web of Science ®Google Scholar
• Andersen LL, Garde AH. (2015). Sleep problems and computer use during work and leisure: Cross-sectional study among 7800 adults. Chronobiol Int. 32:1367–72.
   PubMed Web of Science ®Google Scholar
• Antunes LDC, Jornada MN, Ramalho L, Hidalgo MP. (2010). Correlation of shift work and waist circumference, body mass index, chronotype and depressive symptoms. Arq Bras Endocrinol Metabol. 54:652–6.
   PubMed Web of Science ®Google Scholar
• Antypa N, Vogelzangs N, Meesters Y, Schoevers R, Penninx BW. (2016). Chronotype associations with depression and anxiety disorders in a large cohort study. Depress Anxiety. 33:75–83.
   PubMed Web of Science ®Google Scholar
• Arrona-Palacios A, Garcia A, Valdez P. (2015). Sleep-wake habits and circadian preference in Mexican secondary school. Sleep Med. 16:1259–64.
   PubMed Web of Science ®Google Scholar
• Ashkenazi IE, Reinberg AE, Motohashi Y. (1997). Interindividual differences in the flexibility of human temporal organization: Pertinence to jetlag and shiftwork. Chronobiol Int. 14:99–113.
   PubMed Web of Science ®Google Scholar
• Ayaki M, Hattori A, Maruyama Y, et al. (2016). Protective effect of blue-light shield eyewear for adults against light pollution from self-luminous devices used at night. Chronobiol Int. 33:134–9.
   PubMed Web of Science ®Google Scholar
• Bedrosian TA, Nelson RJ. (2013). Influence of the modern light environment on mood. Mol Psychiatry. 18:751–7.
   PubMed Web of Science ®Google Scholar
• Bei B, Wiley JF, Trindler J, Manber R. (2015). Beyond the mean: A systematic review on the correlates of daily intraindividual variability of sleep/wake patterns. Sleep Med Rev. 28:104–20.
   PubMed Web of Science ®Google Scholar
• Beşoluk S, Onder I, Deveci I. (2011). Morningness-eveningness preferences and academic achievement of university students. Chronobiol Int. 28:118–25.
   PubMed Web of Science ®Google Scholar
• Biss RK, Hasher L. (2012). Happy as a lark: Morning-type younger and older adults are higher in positive affect. Emotion. 12:437–41.
   PubMed Web of Science ®Google Scholar
• Blachnio A, Przepiorka A, Díaz-Morales JF. (2015) Facebook use and chronotype: Results of a cross-sectional study. Chronobiol Int. 32:1315–9.
   PubMed Web of Science ®Google Scholar
• Bolognini M, Plancherel B, Bettschart W, Halfon O. (1996). Self-esteem and mental health in early adolescence: Development and gender differences. J Adolesc. 19:233–45.
   PubMed Web of Science ®Google Scholar
• Bruni O, Sette S, Fontanesi L, Baiocco R, Laghi F, Baumgartner E. (2015). Technology use and sleep quality in preadolescence and adolescence. J Clin Sleep Med. 11:1433–41.
   PubMed Web of Science ®Google Scholar
• Byrd K, Gelaye B, Tadessea MG, Williams MA, Lemma S, Berhanec Y. (2014). Sleep disturbances and common mental disorders in college students. Health Behav Policy Rev. 1:229–37.
   PubMedGoogle Scholar
• Caci H, Robert P, Dossios C, Boyer P. (2005). Morningness-eveningness for children scale: Psychometric properties and month of birth effect. Encephale. 31:56–64.
   PubMed Web of Science ®Google Scholar
• Cajochen C, Frey S, Anders D, et al. (2011). Evening exposure to a light-emitting diodes (LED)-backlit computer screen affects circadian physiology and cognitive performance. J Appl Physiol (1985). 110:1432–8.
   Web of Science ®Google Scholar
• Carrier J, Monk TH, Buysse DJ, Kupfer DJ. (1997). Sleep and morningness-eveningness in the middle years of life (20–59). J Sleep Res. 6:230–7.
   PubMed Web of Science ®Google Scholar
• Concepcion T, Barbosa C, Vélez JC, et al. (2014). Daytime sleepiness, poor sleep quality, eveningness chronotype, and common mental disorders among Chilean college students. J Am Coll Health. 62:441–8.
   PubMed Web of Science ®Google Scholar
• Correa A, Molina E, Sanabria D. (2014). Effects of chronotype and time of day on the vigilance decrement during simulated driving. Accid Anal Prev. 67:113–8.
   PubMed Web of Science ®Google Scholar
• Cortright RN, Lujan HL, Cox JH, DiCarlo SE. (2011). Does sex (female versus male) influence the impact of class attendance on examination performance? Adv Physiol Educ. 35:416–20.
   PubMed Web of Science ®Google Scholar
• de Souza CM, Hidalgo MP. (2014). Midpoint of sleep on school days is associated with depression among adolescents. Chronobiol Int. 31:199–205.
   PubMed Web of Science ®Google Scholar
• de Souza CM, Hidalgo MP. (2015). The midpoint of sleep on working days: A measure for chronodisruption and its association to individual’s well-being. Chronobiol Int. 32:341–8.
   PubMed Web of Science ®Google Scholar
• Delgado Prieto P, Diaz-Morales JF, Escribano BC, Collado Mateo MJ, Randler C. (2012). Morningness-eveningness and health-related quality of life among adolescents. Span J Psychol. 15:613–23.
   PubMed Web of Science ®Google Scholar
• Díaz-Morales JF, Escribano C, Jankowski KS. (2015). Chronotype and time-of-day effects on mood during school day. Chronobiol Int. 32:37–42.
   PubMed Web of Science ®Google Scholar
• Díaz-Morales JF, Escribano C. (2015). Social jetlag, academic achievement and cognitive performance: Understanding gender/sex differences. Chronobiol Int. 32:822–31.
   PubMed Web of Science ®Google Scholar
• Digdon NL, Howell AJ. (2008) College students who have an eveningness preference report lower self-control and greater procrastination. Chronobiol Int. 25:1029–46.
   Google Scholar
• Doi Y, Ishihara K, Uchiyama M. (2015). Associations of chronotype with social jetlag and behavioral problems in preschool children. Chronobiol Int. 32:1101–18.
   PubMed Web of Science ®Google Scholar
• Duarte LL, Menna-Barreto L, Miguel MAL, et al. (2014). Chronotype ontogeny related to gender. Braz J Med Biol Res. 47:316–20.
   PubMed Web of Science ®Google Scholar
• Escribano C, Díaz-Morales JF. (2014). Daily fluctuations in attention at school considering starting time and chronotype: An exploratory study. Chronobiol Int. 31:761–9.
   PubMed Web of Science ®Google Scholar
• Garaulet M, Gomez-Abellan P, Alburquerque-Bejar JJ, Lee YC, Ordovas JM, Scheer FA. (2013). Timing of food intake predicts weight loss effectiveness. Int J Obes (Lond). 37:604–11.
   PubMed Web of Science ®Google Scholar
• Giannotti F, Cortesi F, Sebastiani T, Ottaviano S. (2002). Circadian preference, sleep and daytime behaviour in adolescence. J Sleep Res. 11:191–9.
   PubMed Web of Science ®Google Scholar
• Haraszti RÁ, Ella K, Gyöngyösi N, Roenneberg T, Káldi K. (2014). Social jetlag negatively correlates with academic performance in undergraduates. Chronobiol Int. 31:603–12.
   PubMed Web of Science ®Google Scholar
• Harbard E, Allen NB, Trinder J, Bei B. (2016). What’s keeping teenagers up? Prebedtime behaviors and actigraphy-assessed sleep over school and vacation. J Adolesc Health. 58:426–32.
   PubMed Web of Science ®Google Scholar
• Haregu A, Gelaye B, Pensuksan WC, et al. (2015). Circadian rhythm characteristics, poor sleep quality, daytime sleepiness and common psychiatric disorders among Thai college students. Asia Pac Psychiatry. 7:182–9.
   PubMed Web of Science ®Google Scholar
• Hill AC, Laird AR, Robinson JL. (2014). Gender differences in working memory networks: A BrainMap meta-analysis. Biol Psychol. 102:18–29.
   PubMed Web of Science ®Google Scholar
• Horne JA, Ostberg O. (1976). A self-assessment questionnaire to determine morningness-eveningness in human circadian rhythms. Int J Chronobiol. 4:97–110.
   PubMedGoogle Scholar
• Hsu CY, Gau SS, Shang CY, Chiu YN, Lee MB. (2012). Associations between chronotypes, psychopathology, and personality among incoming college students. Chronobiol Int. 29:491–501.
   PubMed Web of Science ®Google Scholar
• Hwang JK, Kang SG, Gwak AR, Park J, Lee YJ. (2016). The associations of morningness-eveningness with anger and impulsivity in the general population Chronobiol Int. 33:200–9
   Google Scholar
• Kabrita CS, Hajjar-Muça TA, Duffy JF. (2014). Predictors of poor sleep quality among Lebanese university students: Association between evening typology, lifestyle behaviors, and sleep habits. Nat Sci Sleep. 6:11–8.
   PubMedGoogle Scholar
• Kanerva H, Kronholm E, Partonen T, et al. (2012). Tendency toward eveningness is associated with unhealthy dietary habits. Chronobiol Int. 29:920–7.
   PubMed Web of Science ®Google Scholar
• Konttinen H, Kronholm E, Partonen T, Kanerva N, Männistö S, Haukkala A. (2014). Morningness-eveningness, depressive symptoms, and emotional eating: A population-based study. Chronobiol Int. 31:554–63.
   PubMed Web of Science ®Google Scholar
• Koo YS, Song JY, Joo EY, et al. (2016). Outdoor artificial light at night, obesity, and sleep health: Cross-sectional analysis in the KoGES study. Chronobiol Int. 33:301–14.
   Google Scholar
• Kudielka BM, Federenko IS, Hellhammer DH, Wüst S. (2006). Morningness and eveningness: The free cortisol rise after awakening in “early birds” and “night owls”. Biol Psychol. 72:141–6.
   PubMed Web of Science ®Google Scholar
• Larcher S, Benhamou PY, Pepin JL, Borel AL. (2015). Sleep habits and diabetes. Diabetes Metab. 41:263–71.
   PubMed Web of Science ®Google Scholar
• Lehnkering H, Siegmund R. (2007). Influence of chronotype, season, and sex of subject on sleep behavior of young adults. Chronobiol Int. 24:875–88.
   PubMed Web of Science ®Google Scholar
• Levandovski R, Dantas G, Fernandes LC, et al. (2011). Depression scores associate with chronotype and social jetlag in a rural population. Chronobiol Int. 28:771–8.
   PubMed Web of Science ®Google Scholar
• Levandovski R, Sasso E, Hidalgo MP. (2013). Chronotype: A review of the advances, limits and applicability of the main instruments used in the literature to assess human phenotype. Trends Psychiatry Psychother. 35:3–11.
   PubMedGoogle Scholar
• Lin YH, Gau SS. (2013). Association between morningness-eveningness and the severity of compulsive Internet use: The moderating role of gender and parenting style. Sleep Med. 14:1398–404.
   PubMed Web of Science ®Google Scholar
• Lucassen EA, Zhao X, Rother KI, et al. (2013). Evening chronotype is associated with changes in eating behavior, more sleep apnea, and increased stress hormones in short sleeping obese individuals. PLoS One. 8:e56519.
   PubMed Web of Science ®Google Scholar
• Malone SK, Zemel B, Compher C, et al. (2016). Characteristics associated with sleep duration, chronotype, and social jet lag in adolescents. J Sch Nurs. 32:120–31.
   PubMed Web of Science ®Google Scholar
• Martin JS, Hébert M, Ledoux E, Gaudreault M, Laberge L. (2012). Relationship of chronotype to sleep, light exposure, and work-related fatigue in student workers. Chronobiol Int. 29:295–304.
   PubMed Web of Science ®Google Scholar
• Melbin R. (1978). Night as a frontier. Am Sociol Rev. 43:3–22.
   Web of Science ®Google Scholar
• Merikanto I, Kronholm E, Peltonen M, Laatikainen T, Vartiainen E, Partonen T. (2015). Circadian preference links to depression in general adult population. J Affect Disord. 188:143–8.
   PubMed Web of Science ®Google Scholar
• Merikanto I, Lahti T, Kronholm E, et al. (2013a). Evening types are prone to depression. Chronobiol Int. 30:719–25.
   PubMed Web of Science ®Google Scholar
• Merikanto I, Lahti T, Puusniekka R, Partonen T. (2013b). Late bedtimes weaken school performance and predispose adolescents to health hazards. Sleep Med. 14:1105–11.
   PubMed Web of Science ®Google Scholar
• Milić J, Kvolik A, Ivković M, et al. (2014). Are there differences in students’ school success, biorhythm, and daytime sleepiness depending on their school starting times? Coll Antropol. 38:889–94.
   PubMedGoogle Scholar
• Morita Y, Sasai-Sakuma T, Asaoka S, Inoue Y. (2015). The impact of a delayed sleep-wake schedule on depression is greater in women – A web-based cross-sectional study in Japanese young adults. Chronobiol Int. 32:952–8.
   PubMed Web of Science ®Google Scholar
• National Institute for Health and Clinical Excellence. (2011). Common Mental Health Disorders: Identification and Pathways to Care. National Collaborating Centre for Mental Health.
   Google Scholar
• Nielsen T. (2010). Nightmares associated with the eveningness chronotype. J Biol Rhythms. 25:53–62.
   PubMed Web of Science ®Google Scholar
• Nowack K, van der Meer E. (2013). Are larks future-oriented and owls present-oriented? Age- and sex-related shifts in chronotype-time perspective associations. Chronobiol Int. 30:1240–50.
   PubMed Web of Science ®Google Scholar
• Pabst SR, Negriff S, Dorn LD, Susman EJ, Huang B. (2009). Depression and anxiety in adolescent females: The impact of sleep preference and body mass index. J Adolesc Health. 44:554–60.
   PubMed Web of Science ®Google Scholar
• Paine SJ, Gander PH, Travier N. (2006). The epidemiology of morningness/eveningness: Influence of age, gender, ethnicity, and socioeconomic factors in adults (30–49 years). J Biol Rhythms. 21:68–76.
   PubMed Web of Science ®Google Scholar
• Park CI, An SK, Kim HW, et al. (2015). Relationships between chronotypes and affective temperaments in healthy young adults. J Affect Disord. 175:256–9.
   PubMed Web of Science ®Google Scholar
• Ponzi D, Wilson MC, Maestripieri D. (2014). Eveningness is associated with higher risk-taking, independent of sex and personality. Psychol Rep. 115:932–47.
   PubMed Web of Science ®Google Scholar
• Preckel F, Lipnevich AA, Boehme K, et al. (2013). Morningness-eveningness and educational outcomes: The lark has an advantage over the owl at high school. Br J Educ Psychol. 83:114–34.
   PubMed Web of Science ®Google Scholar
• Rahafar A, Maghsudloo M, Farhangnia S, Vollmer C, Randler C. (2016). The role of chronotype, gender, test anxiety, and conscientiousness in academic achievement of high school students. Chronobiol Int. 33:1–9.
   Google Scholar
• Randler C, Bilger S. (2009). Associations among sleep, chronotype, parental monitoring, and pubertal development among German adolescents. J Psychol. 143:509–20.
   PubMed Web of Science ®Google Scholar
• Randler C, Bausback V. (2010). Morningness-eveningness in women around the transition trough menopause and its relationship with climacteric complaints. Biol Rhythm Res. 41:415–31.
   Web of Science ®Google Scholar
• Randler C, Vollmer C. (2013). Aggression in young adults – a matter of short sleep and social jetlag? Psychol Rep. 113:754–65.
   PubMed Web of Science ®Google Scholar
• Randler C. (2008). Evening types among german university students score higher on sense of humor after controlling for big five personality factors. Psychol Rep. 103:361–70.
   PubMed Web of Science ®Google Scholar
• Ray S, Reddy AB. (2016). Cross-talk between circadian clocks, sleep-wake cycles, and metabolic networks: Dispelling the darkness. Bioassays. 38:394–405.
   Google Scholar
• Reske M, Rosenberg J, Plapp S, Kellermann T, Shah NJ. (2015). fMRI identifies chronotype-specific brain activation associated with attention to motion – why we need to know when subjects go to bed. Neuroimage. 111:602–10.
   PubMed Web of Science ®Google Scholar
• Reutrakul S, Hood MM, Crowley SJ, Morgan MK, Teodori M, Knutson KL. (2014). The relationship between breakfast skipping, chronotype, and glycemic control in type 2 diabetes. Chronobiol Int. 31:64–71.
   PubMed Web of Science ®Google Scholar
• Reutrakul S, Knutson KL. (2015). Consequences of circadian disruption on cardiometabolic health. Sleep Med Clin. 10:455–68.
   PubMed Web of Science ®Google Scholar
• Robinson D, Gelaye B, Tadesse MG, Williams MA, Lemma S, Berhane Y. (2013). Daytime sleepiness, circadian preference, caffeine consumption and Khat use among college students in Ethiopia. J Sleep Disord Treat Care. Dec 20;3(1).
   Google Scholar
• Roenneberg T, Allebrandt KV, Merrow M, Vetter C. (2012). Social jet lag and obesity. Curr Biol. 22:939–43.
   PubMed Web of Science ®Google Scholar
• Roenneberg T. (2015). Having trouble typing? What on earth is chronotype? J Biol Rhythms. 30:487–91.
   PubMed Web of Science ®Google Scholar
• Roeser K, Bruckner D, Schwerdtle B, Schlarb AA, Kubler A. (2012). Health-related quality of life in adolescents chronotypes – a model for the effects of sleep problems, sleep-related cognitions, and self-efficacy. Chronobiol Int. 29:1358–65.
   PubMed Web of Science ®Google Scholar
• Rose D, Gelaye B, Sanchez S, et al. (2015). Morningness/eveningness chronotype, poor sleep quality, and daytime sleepiness in relation to common mental disorders among Peruvian college students. Psychol Health Med. 20:345–52.
   PubMed Web of Science ®Google Scholar
• Rybnikova NA, Haim A, Portnov BA. (2016). Does artificial light-at-night (ALAN) exposure contribute to the worldwide obesity pandemic? Int J Obes (Lon). [Epub ahead of print].
   Google Scholar
• Schlarb AA, Sopp R, Ambiel D, Grunwald J. (2014). Chronotype-related differences in childhood and adolescent aggression and antisocial behavior – A review of the literature. Chronobiol Int. 31:1–16.
   PubMed Web of Science ®Google Scholar
• Sheard M. (2009). Hardiness commitment, gender, and age differentiate university academic performance. Br J Educ Psychol. 79:189–204.
   PubMed Web of Science ®Google Scholar
• Sheaves B, Porcheret K, Tsanas A, et al. (2016). Insomnia, nightmares, and chronotype as markers of risk for severe mental illness: Results from a student population. Sleep. 39:173–81.
   PubMed Web of Science ®Google Scholar
• Simor P, Zavecz Z, Pálosi V, Török C, Köteles F. (2015). The influence of sleep complaints on the association between chronotype and negative emotionality in young adults. Chronobiol Int. 32:1–10.
   PubMed Web of Science ®Google Scholar
• Smarr BL. (2015). Digital sleep logs reveal potential impacts of modern temporal structure on class performance in different chronotypes. J Biol Rhythms. 30:61–7.
   PubMed Web of Science ®Google Scholar
• Smolensky MH, Sackett-Lundeen LL, Portaluppi F. (2015). Nocturnal light pollution and underexposure to daytime sunlight: Complementary mechanisms of circadian disruption and related diseases. Chronobiol Int. 32:1029–48.
   PubMed Web of Science ®Google Scholar
• Stolarski M, Jankowski KS, Matthews G, Kawalerczyk J. (2016). Wise “birds” follow their clock: The role of emotional intelligence and morningness-eveningness in diurnal regulation of mood. Chronobiol Int. 33:51–63.
   Google Scholar
• Taylor DJ, Clay KC, Bramoweth AD, Sethi K, Roane BM. (2011). Circadian phase preference in college students: Relationships with psychological functioning and academics. Chronobiol Int. 28:541–7.
   PubMed Web of Science ®Google Scholar
• Thacher PV. (2008). University students and “the all nighter”: Correlates and patterns of students’ engagement in a single night of total sleep deprivation. Behav Sleep Med. 6:16–31.
   PubMed Web of Science ®Google Scholar
• Tonetti L, Natale V, Randler C. (2015). Association between circadian preference and academic achievement: A systematic review and meta-analysis. Chronobiol Int. 32:792–801.
   PubMed Web of Science ®Google Scholar
• Tran J, Lertmaharit S, Lohsoonthorn V, et al. (2014). Daytime sleepiness, circadian preference, caffeine consumption and use of other stimulants among Thai college students. J Public Health Epidemiol. 8:202–10.
   PubMedGoogle Scholar
• Urbán R, Magyaródi T, Rigó A. (2011). Morningness-eveningness, chronotypes and health-impairing behaviors in adolescents. Chronobiol Int. 28:238–47.
   PubMed Web of Science ®Google Scholar
• van der Vinne V, Zerbini G, Siersema A, et al. (2015). Timing of examinations affects school performance differently in early and late chronotypes. J Biol Rhythms. 30:53–60.
   PubMed Web of Science ®Google Scholar
• van Reen E, Sharkey KM, Roane BM, et al. (2013). Sex of college students moderates associations among bedtime, time in bed, and circadian phase angle. J Biol Rhythms. 28:425–31.
   PubMed Web of Science ®Google Scholar
• Vetter C, Devore EE, Ramin CA, Speizer FE, Willett WC, Schernhammer ES. (2015). Mismatch of sleep and work timing and risk of type 2 diabetes. Diabetes Care 38:1707–13.
   PubMed Web of Science ®Google Scholar
• Videnovic A, Zee PC. (2015). Consequences of circadian disruption on neurologic health. Sleep Med Clin. 10:469–80.
   PubMed Web of Science ®Google Scholar
• Vitale JA, Roveda E, Montaruli A, et al. (2015). Chronotype influences activity circadian rhythm and sleep: Differences in sleep quality between weekdays and weekend. Chronobiol Int. 32:405–15.
   PubMed Web of Science ®Google Scholar
• Vollmer C, Michel U, Randler C. (2012). Outdoor light at night (LAN) is correlated with eveningness in adolescents. Chronobiol Int. 29:502–8.
   PubMed Web of Science ®Google Scholar
• Wang L, Chartrand TL. (2015). Morningness-eveningness and risk taking. J Psychol. 149:394–411.
   PubMed Web of Science ®Google Scholar
• Watson NF, Buchwald D, Harden KP. (2013). A twin study of genetic influences on diurnal preference and risk for alcohol use outcomes. J Clin Sleep Med. 9:1333–9.
   PubMed Web of Science ®Google Scholar
• Wennman H, Kronholm E, Partonen T, Peltonen M, Vasankari T, Borodulin K. (2015). Evening typology and morning tiredness associates with low leisure time physical activity and high sitting. Chronobiol Int. 32:1090–100.
   PubMed Web of Science ®Google Scholar
• Whittier A, Sanchez S, Castaneda B, et al. (2014). Eveningness chronotype, daytime sleepiness, caffeine consumption, and use of other stimulants among Peruvian university students. J Caffeine Res. 4:21–7.
   PubMedGoogle Scholar
• Wittmann M, Dinich J, Merrow M, Roenneberg T. (2006). Social jetlag: Misalignment of biological and social time. Chronobiol Int. 23:497–509.
   PubMed Web of Science ®Google Scholar
• Wong PM, Hasler BP, Kamarck TW, Muldoon MF, Manuck SB. (2015). Social jetlag, chronotype, and cardiometabolic risk. J Clin Endocrinol Metab. 100:4612–20.
   PubMed Web of Science ®Google Scholar
• Wood B, Rea MS, Plitnick B, Figueiro MG. (2013). Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression. Appl Ergon. 44:237–40.
   PubMed Web of Science ®Google Scholar
• Yu JH, Yun CH, Ahn JH, et al. (2015). Evening chronotype is associated with metabolic disorders and body composition in middle-aged adults. J Clin Endocrinol Metab. 100:1494–502.
   PubMed Web of Science ®Google Scholar