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Int J Dent Hyg. 2016 Aug;14(3):220-5. doi: 10.1111/idh.12165. Epub 2015 Jul 22.

Do adolescents who are night owls have a higher risk of dental caries? - a case-control study.

Author information

  • 1Public Dental Health Service, Uppsala County Council, Uppsala, Sweden.
  • 2School of Education, Health and Social Studies, Dalarna University, Falun, Sweden.
  • 3The Public Dental Health Service Competence Centre of Northern Norway (TkNN), Tromsø, Norway.



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.


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.


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).


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.


Morningness-eveningness; circadian rhythm; diet habits; oral hygiene

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