title: Review of sleep studies of patients with chronic insomnia at a sleep disorder unit.
abstract: BACKGROUND
  Chronic insomnia is associated with many physical and psychiatric illnesses, and its underlying aetiology needs to be identified in order to achieve safe and effective treatment. Obstructive sleep apnoea (OSA) and periodic limb movement disorder (PLMD) are common primary sleep disorders that can lead to chronic insomnia. Patients with these conditions are evaluated using polysomnography (PSG).
  
  
  METHODS
  The PSG records of 106 patients with chronic insomnia who presented to a multidisciplinary sleep clinic in Singapore over a five-year period were reviewed. To examine the utility of PSG in the evaluation of chronic insomnia, the clinical diagnoses of the patients before and after the sleep studies were compared.
  
  
  RESULTS
  Among the 106 patients, 69 (65.4%) were suspected to have primary sleep disorders based on clinical history and examination alone. Following PSG evaluation, 42.5% and 4.7% of the study population were diagnosed with OSA and PLMD, respectively. OSA was found in 35.9% of the 39 patients who had underlying psychiatric conditions.
  
  
  CONCLUSIONS
  This study illustrates that many patients with chronic insomnia have underlying primary sleep disorders. It also highlights the danger of attributing chronic insomnia in psychiatric patients to their illness, without giving due consideration to other possible aetiologies. Clinicians should maintain a high index of suspicion for the presence of other aetiologies, and make timely and targeted referrals for sleep studies where appropriate.
authors.affiliation: Department of Psychiatry, Singapore General Hospital, Singapore.
authors.forename: Sheau-Hwa
authors.initials: SH
authors.lastname: Wong
authors.affiliation: Department of Psychiatry, Singapore General Hospital, Singapore.
authors.forename: Beng-Yeong
authors.initials: BY
authors.lastname: Ng
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D020189:Nocturnal Myoclonus Syndrome / Q000175:diagnosis*; D017286:Polysomnography / Q000379:methods*; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012846:Singapore; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis*; D007319:Sleep Initiation and Maintenance Disorders / Q000628:therapy*; D012893:Sleep Wake Disorders / Q000175:diagnosis; D016896:Treatment Outcome; D055815:Young Adult
keywords: Singapore; chronic insomnia; obstructive sleep apnoea; polysomnography