title: A case-control field study on the relationships among type 2 diabetes, sleepiness and habitual caffeine intake.
abstract: The purpose of this study was to examine the possible links between type 2 diabetes, daytime sleepiness, sleep quality and caffeine consumption.
  
  
  
  In this case-control field study, comparing type 2 diabetic ( n=134) and non-type 2 diabetic ( n=230) participants, subjects completed detailed and validated questionnaires to assess demographic status, health, daytime sleepiness, sleep quality and timing, diurnal preference, mistimed circadian rhythms and habitual caffeine intake. All participants gave saliva under standardised conditions for CYP1A2 genotyping and quantification of caffeine concentration. Hierarchical linear regression analyses examined whether type 2 diabetes status was associated with caffeine consumption.
  
  
  
  Type 2 diabetic participants reported greater daytime sleepiness ( p=0.001), a higher prevalence of sleep apnoea ( p=0.005) and napping ( p=0.008), and greater habitual caffeine intake ( p<0.001), derived from the consumption of an extra cup of coffee each day. This finding was confirmed by higher saliva caffeine concentration at bedtime ( p=0.01). Multiple regression analyses revealed that type 2 diabetes status was associated with higher self-reported caffeine consumption ( p<0.02) and higher salivary caffeine ( p<0.02). Next to male sex, type 2 diabetes status was the strongest predictor of caffeine intake. Subjective sleep and circadian estimates were similar between case and control groups.
  
  
  
  Type 2 diabetic patients may self-medicate with caffeine to alleviate daytime sleepiness. High caffeine intake reflects a lifestyle factor that may be considered when promoting type 2 diabetes management.
authors.affiliation: 1 Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland.|2 Zürich Center for interdisciplinary Sleep Research, University of Zürich, Zürich, Switzerland.|3 Department of Health Sciences and Technology, ETH Zürich, Zürich, Switzerland.
authors.forename: Emily
authors.initials: E
authors.lastname: Urry
authors.affiliation: 4 Department of Clinical Pharmacology and Toxicology, University Hospital Zürich, Zürich, Switzerland.
authors.forename: Alexander
authors.initials: A
authors.lastname: Jetter
authors.affiliation: 1 Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland.|2 Zürich Center for interdisciplinary Sleep Research, University of Zürich, Zürich, Switzerland.
authors.forename: Sebastian C
authors.initials: SC
authors.lastname: Holst
authors.affiliation: 5 Institute of Medical Molecular Genetics, University of Zürich, Zürich, Switzerland.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Berger
authors.affiliation: 6 Division of Endocrinology, Diabetes and Clinical Nutrition, University Hospital Zürich, Zürich, Switzerland.
authors.forename: Giatgen A
authors.initials: GA
authors.lastname: Spinas
authors.affiliation: 3 Department of Health Sciences and Technology, ETH Zürich, Zürich, Switzerland.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Langhans
authors.affiliation: 1 Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Switzerland.|2 Zürich Center for interdisciplinary Sleep Research, University of Zürich, Zürich, Switzerland.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Landolt
mesh_terms: D002110:Caffeine / Q000008:administration & dosage*; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000187:drug effects; D003069:Coffee; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism / Q000503:physiopathology*; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D012463:Saliva / Q000378:metabolism; D012890:Sleep / Q000187:drug effects*; D011795:Surveys and Questionnaires; D014851:Wakefulness / Q000187:drug effects
chemical_list: D003069:Coffee; D002110:Caffeine; D019388:Cytochrome P-450 CYP1A2
keywords: Vigilance; chronotype; coffee; cytochrome P450-1A2 genotype; high performance liquid chromatography; metabolism; sleep apnoea