title: Comorbid depression is associated with an increased risk of dementia diagnosis in patients with diabetes: a prospective cohort study.
abstract: BACKGROUND
  Both depression and diabetes have been found to be risk factors for dementia. This study examined whether comorbid depression in patients with diabetes increases the risk for dementia compared to those with diabetes alone.
  
  
  METHODS
  We conducted a prospective cohort study of 3,837 primary care patients with diabetes (mean age 63.2 +/- 13.2 years) enrolled in an HMO in Washington State. The Patient Health Questionnaire (PHQ-9) was used to assess depression at baseline, and ICD-9 diagnoses for dementia were used to identify cases of dementia. Cohort members with no previous ICD-9 diagnosis of dementia prior to baseline were followed for a 5-year period. The risk of dementia for patients with both major depression and diabetes at baseline relative to patients with diabetes alone was estimated using cause-specific Cox proportional hazard regression models that adjusted for age, gender, education, race/ethnicity, diabetes duration, treatment with insulin, diabetes complications, nondiabetes-related medical comorbidity, hypertension, BMI, physical inactivity, smoking, HbA(1c), and number of primary care visits per month.
  
  
  RESULTS
  Over the 5-year period, 36 of 455 (7.9%) patients with major depression and diabetes (incidence rate of 21.5 per 1,000 person-years) versus 163 of 3,382 (4.8%) patients with diabetes alone (incidence rate of 11.8 per 1,000 person-years) had one or more ICD-9 diagnoses of dementia. Patients with comorbid major depression had an increased risk of dementia (fully adjusted hazard ratio 2.69, 95% CI 1.77, 4.07).
  
  
  CONCLUSIONS
  Patients with major depression and diabetes had an increased risk of development of dementia compared to those with diabetes alone. These data add to recent findings showing that depression was associated with an increased risk of macrovascular and microvascular complications in patients with diabetes.
authors.affiliation: Department of Psychiatry & Behavioral Sciences, University of Washington School of Medicine, 1959 NE Pacific Street, Box 356560, Seattle, WA 98195-6560, USA. wkaton@u.washington.edu
authors.forename: Wayne J
authors.initials: WJ
authors.lastname: Katon
authors.forename: Elizabeth H B
authors.initials: EH
authors.lastname: Lin
authors.forename: Lisa H
authors.initials: LH
authors.lastname: Williams
authors.forename: Paul
authors.initials: P
authors.lastname: Ciechanowski
authors.forename: Susan R
authors.initials: SR
authors.lastname: Heckbert
authors.forename: Evette
authors.initials: E
authors.lastname: Ludman
authors.forename: Carolyn
authors.initials: C
authors.lastname: Rutter
authors.forename: Paul K
authors.initials: PK
authors.lastname: Crane
authors.forename: Malia
authors.initials: M
authors.lastname: Oliver
authors.forename: Michael
authors.initials: M
authors.lastname: Von Korff
mesh_terms: D000368:Aged; D015331:Cohort Studies; D015897:Comorbidity; D003704:Dementia / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology / Q000523:psychology; D003865:Major Depressive Disorder / Q000150:complications / Q000453:epidemiology* / Q000523:psychology; D048909:Diabetes Complications / Q000453:epidemiology* / Q000523:psychology; D003920:Diabetes Mellitus / Q000453:epidemiology* / Q000523:psychology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors