title: U-shaped association of sleep duration with metabolic syndrome and insulin resistance in patients with type 2 diabetes: the Fukuoka Diabetes Registry.
abstract: OBJECTIVE
  Sleep duration is suggested to be associated with adverse health outcomes. However, few studies are available on the impact of sleep duration on metabolic syndrome in patients with diabetes, who were at high risk for cardiovascular diseases (CVD). The objective of the present study was to examine the associations of sleep duration with metabolic syndrome and insulin resistance, a major pathophysiologic feature of metabolic syndrome, in patients with type 2 diabetes.
  
  
  METHODS
  A total of 4402 Japanese patients with type 2 diabetes aged ≥20years were divided into 5 groups according to self-reported sleep duration: less than 5.5h, 5.5-6.4h, 6.5-7.4h, 7.5-8.4h, and more than 8.5h. The associations of sleep duration with metabolic syndrome and other cardiovascular risk factors were examined cross-sectionally.
  
  
  RESULTS
  The proportions of patients who had metabolic syndrome increased significantly in both patients with shorter and longer sleep duration compared with those with 6.5-7.4h of sleep (P for quadratic trend <0.001). This U-shaped association remained significant after adjustment for potential confounders, including total energy intake, current smoking, current drinking and depressive symptoms. Each component of metabolic syndrome also showed similar trends. Furthermore, sleep duration had a quadratic association with homeostasis model assessment of insulin resistance and high sensitivity C-reactive protein.
  
  
  CONCLUSIONS
  Sleep duration was shown to have a U-shaped relationship with metabolic syndrome and insulin resistance, independent of potential confounders, and therefore may be an important modifiable risk factor for CVD prevention in patients with type 2 diabetes.
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; Department of Internal Medicine, Fukuoka Dental College Medical and Dental Hospital, Fukuoka, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Ohkuma
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Fujii
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan; Diabetes Center, Hakujyuji Hospital, Fukuoka, Japan. Electronic address: iwase@intmed2.med.kyushu-u.ac.jp.
authors.forename: Masanori
authors.initials: M
authors.lastname: Iwase
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Shinako
authors.initials: S
authors.lastname: Ogata-Kaizu
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ide
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Kikuchi
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Idewaki
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Tamaki
authors.initials: T
authors.lastname: Jodai
authors.affiliation: Department of Environmental Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Hirakawa
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Udai
authors.initials: U
authors.lastname: Nakamura
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Takanari
authors.initials: T
authors.lastname: Kitazono
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000453:epidemiology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D007564:Japan / Q000453:epidemiology; D008297:Male; D024821:Metabolic Syndrome / Q000150:complications / Q000453:epidemiology / Q000503:physiopathology*; D008875:Middle Aged; D011446:Prospective Studies; D012042:Registries; D012890:Sleep
keywords: C-reactive protein; Cardiovascular risk; Epidemiology; Sleep; Type 2 diabetes mellitus