title: Mortality and secular trend in the incidence of bipolar disorder.
abstract: BACKGROUND
  The world-wide interest in bipolar disorder is illustrated by an exponential increase in publications on the disorder registered in Pubmed since 1990. This inspired an investigation of the epidemiology of bipolar disorder.
  
  
  METHODS
  This was a register-based cohort study. All first-ever diagnoses of bipolar disorder (International Classification of Diseases-10: F31) were identified in the nationwide Danish Psychiatric Central Research Register between 1995 and 2012. Causes of death were obtained from The Danish Register of Causes of Death. Age- and gender standardized incidence rates, standardized mortality ratio (SMR) and Kaplan-Meier survival estimates were calculated.
  
  
  RESULTS
  We identified 15,334 incident cases of bipolar disorder. The incidence rate increased from 18.5/100,000 person-years (PY) in 1995 to 28.4/100,000 PY in 2012. The mean age at time of diagnosis decreased significantly from 54.5 years in 1995 to 42.4 years in 2012 (p<0.001). The mean time from first affective diagnosis to diagnosis of bipolar disorder was 7.9 years (SD 9.1). The SMR was 1.7 (95%-CI 1.2-2.1). Causes of death were mainly natural; 9% died from suicide.
  
  
  CONCLUSIONS
  Only patients in psychiatric care were included. The outpatient registry opened in 1995. Patients treated solely in outpatient units are not recorded previously. Systematic studies validating all the clinical diagnoses of the registry do not exist.
  
  
  CONCLUSIONS
  The incidence of bipolar disorder has increased in the last 10 years. The SMR was significantly increased. Half of the patients were known to have another affective disorder. This should be considered in future decisions regarding the healthcare organization.
authors.affiliation: Aarhus University Hospital, Risskov, Denmark. Electronic address: Clara.reece.medici@post.au.dk.
authors.forename: Clara Reece
authors.initials: CR
authors.lastname: Medici
authors.affiliation: Psychiatric Center Glostrup, Glostrup, Denmark.
authors.forename: Poul
authors.initials: P
authors.lastname: Videbech
authors.affiliation: Aarhus University Hospital, Risskov, Denmark.
authors.forename: Lea Nørgreen
authors.initials: LN
authors.lastname: Gustafsson
authors.affiliation: Aarhus University Hospital, Risskov, Denmark.
authors.forename: Povl
authors.initials: P
authors.lastname: Munk-Jørgensen
mesh_terms: D000368:Aged; D001714:Bipolar Disorder / Q000401:mortality*; D015984:Causality; D002423:Cause of Death / Q000639:trends; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D038801:International Classification of Diseases; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D019964:Mood Disorders / Q000401:mortality; D012042:Registries / Q000706:statistics & numerical data*; D013405:Suicide / Q000706:statistics & numerical data* / Q000639:trends; D055815:Young Adult
keywords: Age distribution; Bipolar disorder; Causes of death; Incidence; Mortality; Registries