Subtypes of depression among patients with Alzheimer's disease and other dementias.

OBJECTIVES

We compared the prevalence of subtypes of depression in patients with Alzheimer's disease (AD), vascular dementia (VaD), and unspecified dementia (UD).

METHODS

Using the Integrated Healthcare Information Services database, we conducted an analysis of subtypes of depression (major depressive disorder, depressive disorder not otherwise specified, dysthymic disorder; depressive psychosis, and adjustment disorder depressive) among patients with AD, VaD, and UD. Six thousand four hundred and forty patients aged 60 years or older with dementia (2947 with AD, 725 with VaD, and 2768 with UD) were identified from January 1 to December 31, 2001. Both subtypes of depression and dementia subgroups were diagnosed using criteria from the International Classification of Diseases, 9th version.

RESULTS

The overall prevalence of depressive disorders was 27.41%. The prevalence of depressive disorders was significantly higher in VaD (44.14%) and UD (32.48%) patients compared with AD (18.53%, P < .0001) patients. The AD patients had the lowest prevalence of all subtypes of depression. The VaD patients, compared with both AD and UD (P < .005), had a significantly higher prevalence of: 1) depressive disorder not otherwise specified, 2) major depressive disorder, and 3) dysthymic disorder. Adjustment disorder with depressive symptoms was more common in the UD subgroup, whereas the rate of depressive psychosis was similar in all dementia subgroups

CONCLUSIONS

This study supports the view that depressive disorders are more prevalent in VaD compared with UD and AD, and provides indicators to the clinician for further evaluation of depression in dementia subgroups.