Depression in elderly patients with Alzheimer dementia or vascular dementia and its influence on their quality of life

Study design

We recruited consecutive patients with Alzheimer dementia (AD) or vascular dementia (VD) (n=98), which are the most prevalent types of dementia. Diagnosis of AD and VD was based on criteria proposed by the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA Alzheimer's Criteria).[67]

Patients were recruited in the Department of Psychiatry and Psychosomatics, Sklifosovski Research Institute, Moscow, Russia. The study design was approved by the local ethic committees and all patients gave informed consent for participation.

Clinical evaluation

Patients with AD or VD received a complete medical and neurological examination performed by a specialist (study investigator) with at least five years experience in dementia.

All clinical and demographic data were documented in specially developed case report forms (CRFs). The CRF included the following parts:

1. Demographics and social data.

2. Clinical data (disease onset, duration of disease, time from first manifestation to diagnosis, severity scales and co-morbid disorders)

3. Depression scale (Geriatric Depression Scale)

4. Health-related quality of life measurements (EQ-5D).

Severity of cognitive impairment was evaluated using the Mini-Mental State Examination (MMSE), which is a valid and most common tool for assessment of cognitive deficits in dementia.[8] Depression was diagnosed according to criteria of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) [Table 1]. Severity of depressive symptoms was measured using the Geriatric Depression Scale. The Geriatric Depression Scale (GDS) is a standardized and validated self-report questionnaire used to identify depression in the elderly. It is based on yes-or-no questions regarding mood over the previous week with higher scores on GDS indicating more severe depression.[9] The test allows 84% sensitivity and 95% specificity in detection of depression. The following cut-offs for GDS were used: score of 0–9 is considered normal; 10–19 indicates mild depression, and a score ≥20 indicates severe depression.

Table 1 DSM-IV criteria for major depressive episode

Health-related quality of life

The evaluation of HrQoL was performed using EuroQol. The EuroQol is a valid standardized health state measure.[10] It consists of a self-classifier (EQ-5D) and a visual analogue scale (VAS). The self-classifier evaluates five dimensions of health: mobility, self-care, usual activities, pain/discomfort and anxiety/depression.[1112] Each dimension is divided into three levels of severity (1=no problem, 2=moderate problem, 3=severe problem). The EQ-5D-index score was calculated according to the European recommendations.[13] The visual analogue scale is a thermometer type scale ranging from 0 (worst imaginable health state) to 100 (best imaginable health state).[14]

Statistical analysis

Statistical analysis was performed using SPSS Version 15.0 (SPSS Inc., Chicago, IL, USA).All data are presented as mean, standard deviation (SD) and median. The Kolmogorov-Smirnov test was used to test the data for normal distribution. For group comparisons of data not following normal distribution, either the Mann-Whitney U test (two independent groups), the Kruskal Wallis test (more than two independent groups) or the Wilcoxon rank test (two dependent groups) were applied. Significance level was set at 5%. Multiple regression analysis was used to identify factors predicting severity of depression. The R² method was used to explore the variability accounted for by predicting factors.[15]

Sociodemographic and clinical data

The age of the study participants with AD or VD was 77.5±8.8 years. The proportion of female patients was 65.3%. Demographics and clinical data are shown in Table 2. More than 90% of patients were age retired. The proportion of widowed patients increased with growing age. Forty-four percent of patients (n=43) with AD or VD were widowed.

Table 2 Demographics and clinical characteristics

In study population, 84.7% (n=83) patients had moderate cognitive impairment (MMSE≥14) and 15.3% (n=15) had severe cognitive deficits (MMSE<14). Extrapyramidal symptoms had 73.5% (n=72) of patients. Behavioral disorders were present in 43.9% (n=43) patients.

Depression and health-related quality of life

The prevalence of depressive symptoms in patients with AD or VD was 86.7% (n=85). Fifty-six percent (n=55) of patients had moderate depression and 36% (n=35) of patients had severe depression as measured on the GDS. The prevalence of other mental disorders in the study population was lower: 30.6% (n=30) of patients had psychotic symptoms, 43.9% (n=43) of patients had behavioral disorders, 9.2% (n=9) of patients had alcohol dependency. Only 40% of patients with manifest depression were provided with adequate antidepressant treatment.

The health-related quality of life was considerably reduced in our patients with AD or VD. In dimensions of “mobility”, “self-care”, “usual activities”, “pain/discomfort” and “anxiety/depression” of the EQ-5D, severe problems were found in 25.5%, 32.7%, 36.7%, 14.3% and 20.4% of patients, respectively. The mean EQ-5D index score was 36.7±18.5. The mean score on the EQ-VAS was significantly decreased in comparison to the general population (34.0±13.8 versus 77.0±20.8, P<0.01).[16] The association between HrQoL and age is shown in Table 3. The values on the EQ-VAS and EQ-5D index decreased with increasing age. No associations between gender and HrQoL were revealed.

Table 3 Association of quality of life scores with age, gender and depression

In the dimension “anxiety/depression” of the EQ-5D, 81% of patients with AD or VD had moderate or severe problems. Depression showed a strong association with reduced HrQoL [Table 3]. The presence of depression reduced the HrQoL in patients with AD or VD by 14% (P<0.01).

Multiple regression analysis identified age, gender, MMSE and marital status to be independent predictors of depression severity in AD or VD [Table 4]. All together, these four variables could explain 33.5% of variability in scores on the GDS. Older age and male gender were associated with more severe depression. Married patients had lower prevalence of depression. Employment status was not associated with depression. Interestingly, the severity of depression had a reverse association with severity of cognitive impairment [Table 4 and Figure 1].

Table 4 Multiple regression analysis of factors predicting severity of depression

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Figure 1

Measures on the geriatric depression scale depending on severity of dementia

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Our study has some limitations

Referral-based design was used for recruitment. An epidemiological study with door-to-door data collection would provide more precise data. We cannot exclude a selection bias towards more severe disease stages in our sample. Patients with minimal cognitive deficits (MCI) or those in early stages of dementia less often consult general practitioners, neurologists or psychiatrists. We applied a generic HRQoL instrument (EuroQol), which is less sensitive to disease-specific changes of health-related quality of life. However, we sought to evaluate the general HRQoL and provide data suitable for a comparison between these patients and the general population. Mini Mental State Examination is a less specific tool for assessment of cognitive deficits in AD than ADAS-Cog and is also less specific than VADAS-Cog in VD. However, MMSE is a valid and well-known measure for estimation of cognitive impairment in different types of dementia. We included patients with two different types of dementia and applied one standardized instrument (MMSE) instead of two disease-specific measures in order to collect homogenous neuropsychological data. The cross-sectional design of our study does not provide any information on changes in depression severity and HRQoL over time.