title: Do adolescents who are night owls have a higher risk of dental caries? - a case-control study.
abstract: OBJECTIVE
  The aim was to evaluate the association between circadian rhythm and the risk of caries in adolescents, as well as their dietary and toothbrushing habits.
  
  
  METHODS
  A group of 196 adolescents (15 and 16 years old) were divided into two equal groups based on caries risk (case = high risk; and control = low risk). Before their dental examinations, they were asked to complete a questionnaire. The questionnaire included questions on circadian rhythm, dietary and oral self-care habits, and demographic variables. The participants were divided into three circadian types: evening types who are alert in the evening and tired in the morning; morning types who are the opposite; and neutral types who are neither particularly alert in the evening nor extremely tired in the morning.
  
  
  RESULTS
  The most common sleep-cycle group type was neutral (50%). After this came evening types (37%) and finally morning types (13%). Morning and neutral types reported more frequently than evening types that they had breakfast every morning and brushed their teeth twice a day. More evening types were categorized as at high risk of caries. Circadian rhythm, breakfast habits and toothbrushing frequency were associated with a high risk of caries. The predicted probability of being at high risk of caries was almost four times higher for evening types than for morning types (OR 3.8; 95% CI 1.3-10.9).
  
  
  CONCLUSIONS
  Adolescents who belonged to the evening circadian rhythm group brushed their teeth more seldom, ate breakfast less regularly and had a higher risk of caries than morning types. A patient's circadian rhythm should be considered when planning oral health education for adolescents with a high risk of caries.
authors.affiliation: Public Dental Health Service, Uppsala County Council, Uppsala, Sweden.
authors.forename: A-M
authors.initials: AM
authors.lastname: Lundgren
authors.affiliation: School of Education, Health and Social Studies, Dalarna University, Falun, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Öhrn
authors.affiliation: School of Education, Health and Social Studies, Dalarna University, Falun, Sweden.|The Public Dental Health Service Competence Centre of Northern Norway (TkNN), Tromsø, Norway.
authors.forename: B
authors.identifier: http://orcid.org/0000-0002-7781-8527
authors.initials: B
authors.lastname: Jönsson
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D016022:Case-Control Studies; D002940:Circadian Rhythm; D003430:Cross-Sectional Studies; D003731:Dental Caries / Q000453:epidemiology*; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D009910:Oral Hygiene / Q000193:education / Q000706:statistics & numerical data; D018570:Risk Assessment; D012648:Self Care; D012890:Sleep / Q000502:physiology; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors; D014099:Toothbrushing
keywords: Morningness-eveningness; circadian rhythm; diet habits; oral hygiene