title: An investigation of the associations among sleep duration and quality, body mass index and insulin resistance in newly diagnosed type 2 diabetes mellitus patients.
abstract: OBJECTIVE
  To examine direct and indirect associations of sleep duration and quality with insulin resistance, considering body mass index (BMI) as a potential mediator in newly diagnosed type 2 diabetes mellitus patients.
  
  
  METHODS
  Cross-sectional data from patients enrolled in the Early Activity in Diabetes study. We studied 522 newly diagnosed type 2 diabetes mellitus patients, 65.9% male, mean age 63.5 ± 10.1 years. Of the total sample 53% had a BMI of ⩾30 kg/m(2). Participants completed a 7-day sleep diary and sleep questionnaire. Average sleep duration (minutes), average nap duration (minutes) and average number of night awakenings were derived. Objective measures of height and body weight were obtained for the BMI calculation (kg/m(2)). Insulin resistance was obtained using the homeostatic model assessment - insulin resistance (HOMA2-IR) standardized technique.
  
  
  RESULTS
  Average number of night awakenings was positively correlated with BMI (r= 0.22, p < 0.001) and negatively associated with logged HOMA2-IR (r= -0.16, p = 0.04). Path analysis demonstrated night awakenings were directly associated with BMI and indirectly associated with insulin resistance, whilst considering BMI as a potential mediator (p < 0.05). Sleep duration was not associated with BMI or insulin resistance (p > 0.05).
  
  
  CONCLUSIONS
  Sleep quality, not sleep duration, plays an important role in insulin resistance in newly diagnosed type 2 diabetes mellitus patients. BMI may mediate the relationship between indicators of sleep quality and insulin resistance. There is a need to examine the impact of improving sleep quality on obesity and insulin resistance in patients with type 2 diabetes mellitus.
authors.affiliation: Weill Cornell Medicine in Qatar and New York, USA.
authors.forename: Teresa
authors.initials: T
authors.lastname: Arora
authors.affiliation: School of Clinical Sciences, University of Bristol, UK.
authors.forename: Mimi Z
authors.initials: MZ
authors.lastname: Chen
authors.affiliation: Weill Cornell Medicine in Qatar and New York, USA.
authors.forename: Omar M
authors.initials: OM
authors.lastname: Omar
authors.affiliation: National Institute for Health Research, Bristol Biomedical Research Unit in Nutrition, Diet and Lifestyle Centre for Exercise, Nutrition and Health Sciences, School for Policy Studies, University of Bristol, UK.
authors.forename: Ashley R
authors.initials: AR
authors.lastname: Cooper
authors.affiliation: School of Clinical Sciences, University of Bristol, UK.
authors.forename: Rob C
authors.initials: RC
authors.lastname: Andrews
authors.affiliation: Weill Cornell Medicine in Qatar, Qatar Foundation, Education City, PO Box 24144, Doha, Qatar.
authors.forename: Shahrad
authors.initials: S
authors.lastname: Taheri
keywords: body mass index; insulin resistance; sleep quality