title: Fatigue in non-alcoholic fatty liver disease (NAFLD) is significant and associates with inactivity and excessive daytime sleepiness but not with liver disease severity or insulin resistance.
abstract: OBJECTIVE
  To quantify fatigue in non-alcoholic fatty liver disease (NAFLD), to determine whether perceived fatigue reflects impairment of physical function and to explore potential causes.
  
  
  METHODS
  A cohort study was carried out on 156 consecutive patients with histologically proven NAFLD studied in two cohorts. Phase 1 determined the perceived fatigue experienced by NAFLD patients (assessed using the Fatigue Impact Scale (FIS)) in comparison with normal and liver disease controls, and the relationship to physical function (actigraphy). In phase 2, biological associations of fatigue in NAFLD were explored.
  
  
  RESULTS
  Fatigue was markedly higher in NAFLD patients than in controls (mean (SD) FIS 51 (38) vs 8 (12), p<0.001). NAFLD patients showed significantly lower physical activity over 6 days (7089 (2909) mean steps/day vs 8676 (2894), p = 0.02). A significant inverse correlation was seen between FIS and physical activity (r = 0.1, p = 0.02). Fatigue experienced by NAFLD patients was similar to that in primary biliary cirrhosis (n = 36) (FIS 64 (9) vs 61 (2), p = NS). No association was seen between FIS and biochemical and histological markers of liver disease severity or insulin resistance (homeostasis model assessment (HOMA)) (r < 0.005). Significant association was seen between fatigue severity and daytime somnolence (Epworth Sleepiness Scale) (r = 0.2, p < 0.001).
  
  
  CONCLUSIONS
  Fatigue is a significant problem in NAFLD, is similar in degree to that in primary biliary cirrhosis patients and is associated with impairment in physical function. Fatigue in NAFLD appears to be unrelated to either severity of underlying liver disease or insulin resistance, but is associated with significant daytime somnolence.
authors.affiliation: Care of the Elderly Offices, Royal Victoria Infirmary, Newcastle NE1 4LP, UK. julia.newton@nuth.northy.nhs.uk
authors.forename: J L
authors.initials: JL
authors.lastname: Newton
authors.forename: D E J
authors.initials: DE
authors.lastname: Jones
authors.forename: E
authors.initials: E
authors.lastname: Henderson
authors.forename: L
authors.initials: L
authors.lastname: Kane
authors.forename: K
authors.initials: K
authors.lastname: Wilton
authors.forename: A D
authors.initials: AD
authors.lastname: Burt
authors.forename: C P
authors.initials: CP
authors.lastname: Day
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D006970:Disorders of Excessive Somnolence / Q000150:complications*; D005221:Fatigue / Q000209:etiology* / Q000503:physiopathology; D005234:Fatty Liver / Q000150:complications* / Q000503:physiopathology; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D005082:Physical Exertion; D012720:Severity of Illness Index