The prevalence of depression in Alzheimer's disease and vascular dementia in a population sample.

BACKGROUND

Previous studies have shown that depression is more prevalent in vascular dementia than Alzheimer's disease (AD). Subjects for these studies were either psychiatry or neurology patients, raising the issue of whether factors leading to treatment might have introduced sampling bias.

METHODS

Data for the present study came from the Canadian Study of Health and Aging (CSHA, 1994), a population-based prevalence study of dementia. AD was diagnosed using NINCDS-ADRDA criteria (McKhann et al., 1984), vascular dementia was diagnosed using draft ICD-10 criteria (World Health Organization, 1987) and the Ischemic Scale (Hachinski et al., 1975), major depression was diagnosed using an algorithm based on DSM-III-R criteria (American Psychiatric Association, 1987). The sample for the present study consisted of 481 subjects with AD and 140 with vascular dementia.

RESULTS

The weighted prevalence rate of major depression was 3.2% for AD and 21.2% for vascular dementia, giving a crude odds ratio of 8.2 (95% Confidence Interval: 1.7-40.2). This finding was confirmed by a logistic regression analysis which adjusted for age, sex, place of residence (community, institution), self-reported health, severity of cognitive impairment, and antidepressant or beta-blocker use.

LIMITATIONS

Data on depressive symptoms were more often missing in subjects with dementia resulting in differential loss of potential study subjects. Data on depressive symptoms were not sufficiently detailed to permit DSM-III-R criteria to be implemented rigorously. The method of diagnosing vascular dementia was subject to misclassification.

CONCLUSIONS

This study confirms in a population sample that depression is more prevalent in vascular dementia compared to AD.