title: Record-linkage studies of the coexistence of epilepsy and bipolar disorder.
abstract: OBJECTIVE
  Interest is growing in a possible link between epilepsy and bipolar disorder (BPD). We used two large datasets of hospital admission data to determine whether epilepsy and BPD occur together in the same individuals more commonly than expected.
  
  
  METHODS
  We undertook retrospective cohort studies using the Oxford Record Linkage Study (ORLS) and English national linked Hospital Episode Statistics. We constructed a cohort of people in each dataset admitted with epilepsy (without prior admission for BPD), and a control cohort (without prior admission for BPD), and compared their subsequent admission rates for BPD. Conversely, we constructed a cohort of people in each dataset admitted with BPD and a control cohort (both without prior admission for epilepsy), and compared their subsequent admission rates for epilepsy.
  
  
  RESULTS
  In the epilepsy cohort, compared with the control cohort, the rate ratio (RR) for BPD was significantly high at 3.0 (95 % confidence interval 1.7-5.1) in the ORLS and 3.6 (3.3-3.9) in the all-England dataset. In the BPD cohort, the RR for epilepsy was 2.2 (1.2-3.7) in the ORLS and 4.2 (4.0-4.4) in the all-England cohort. We found no significant differences between RRs for males and females.
  
  
  CONCLUSIONS
  Epilepsy and BPD occur together in individuals more frequently than expected by chance.
authors.affiliation: Unit of Health-Care Epidemiology, Nuffield Department of Population Health, University of Oxford, Old Road Campus, Old Road, Oxford, OX3 7LF, UK, clare.wotton@dph.ox.ac.uk.
authors.forename: Clare J
authors.initials: CJ
authors.lastname: Wotton
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Goldacre
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001714:Bipolar Disorder / Q000150:complications* / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D004739:England / Q000453:epidemiology; D004827:Epilepsy / Q000150:complications* / Q000453:epidemiology; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008498:Medical Record Linkage; D008875:Middle Aged; D012189:Retrospective Studies; D055815:Young Adult