title: Evaluation of latent links between irritable bowel syndrome and sleep quality.
abstract: OBJECTIVE
  To examine the links between quality of sleep and the severity of intestinal symptoms in irritable bowel syndrome (IBS).
  
  
  METHODS
  One hundred and forty-two outpatients (110 female, 32 male) who met the Rome III criteria for IBS with no psychiatric comorbidity were consecutively enrolled in this study. Data on age, body mass index (BMI), and a set of life-habit variables were recorded, and IBS symptoms and sleep quality were evaluated using the questionnaires IBS Symptom Severity Score (IBS-SSS) and Pittsburgh Sleep Quality Index (PSQI). The association between severity of IBS and sleep disturbances was evaluated by comparing the global IBS-SSS and PSQI score (Pearson's correlation and Fisher's exact test) and then analyzing the individual items of the IBS-SSS and PSQI questionnaires by a unitary bowel-sleep model based on item response theory (IRT).
  
  
  RESULTS
  IBS-SSS ranged from mild to severe (120-470). The global PSQI score ranged from 1 to 17 (median 5), and 60 patients were found to be poor sleepers (PSQI > 5). The correlation between the global IBS-SSS and PSQI score indicated a weak association (r = 0.2 and 95% CI: -0.03 to 0.35, P < 0.05), which becomes stronger using our unitary model. Indeed, the IBS and sleep disturbances severities, estimated as latent variables, resulted significantly high intra-subject correlation (posterior mean of r = 0.45 and 95% CI: 0.17 to 0.70, P < 0.05). Moreover, the correlations between patient features (age, sex, BMI, daily coffee and alcohol intake) and IBS and sleep disturbances were also analyzed through our unitary model. Age was a significant regressor, with patients ≤ 50 years old showing more severe bowel disturbances (posterior mean = -0.38, P < 0.05) and less severe sleep disturbances (posterior mean = 0.49, P < 0.05) than older patients. Higher daily coffee intake was correlated with a lower severity of bowel disturbances (posterior mean = -0.31, P < 0.05). Sex (female) and daily alcohol intake (modest) were correlated with less severe sleep disturbances.
  
  
  CONCLUSIONS
  The unitary bowel-sleep model based on IRT revealed a strong positive correlation between the severity of IBS symptoms and sleep disturbances.
authors.affiliation: Gastrointestinal Unit, Department of Gastroenterology, University of Pisa, 56100 Pisa, Italy. mbellini@med.unipi.it
authors.forename: Massimo
authors.initials: M
authors.lastname: Bellini
authors.forename: Angelo
authors.initials: A
authors.lastname: Gemignani
authors.forename: Dario
authors.initials: D
authors.lastname: Gambaccini
authors.forename: Simona
authors.initials: S
authors.lastname: Toti
authors.forename: Danilo
authors.initials: D
authors.lastname: Menicucci
authors.forename: Cristina
authors.initials: C
authors.lastname: Stasi
authors.forename: Francesco
authors.initials: F
authors.lastname: Costa
authors.forename: Maria Gloria
authors.initials: MG
authors.lastname: Mumolo
authors.forename: Angelo
authors.initials: A
authors.lastname: Ricchiuti
authors.forename: Remo
authors.initials: R
authors.lastname: Bedini
authors.forename: Nicola
authors.initials: N
authors.lastname: de Bortoli
authors.forename: Santino
authors.initials: S
authors.lastname: Marchi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000150:complications / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D012720:Severity of Illness Index; D012890:Sleep / Q000502:physiology*; D012893:Sleep Wake Disorders / Q000209:etiology / Q000503:physiopathology*; D011795:Surveys and Questionnaires; D055815:Young Adult