FACTOR ANALYSIS OF THE GERIATRIC DEPRESSION SCALE (GDS-15)

Geriatric depression is known to be one of the most common psychiatric disorders in old age that negatively affects the quality of life, increases mortality, morbidity and worsens cognitive abilities. Due to the specific features of geriatric depression, there is a need to introduce screening methods to be used specifically for the older people. One of the commonly used questionnaire methods in older persons is the 15-item Geriatric Depression Scale (GDS-15). The Czech version of GDS-15 is now in the process of standardization. Here, we present its factor structure. Methods: 538 mentally healthy seniors aged 60 and over, the original participants of the National Normative Study of Cognitive Determinants of Healthy Aging (NANOK) and the Impact of Urbanization on Cognitive Performance in the Elderly (COURAGE), completed a GDS-15 questionnaire. For GDS-15 analysis, explorative factor analysis with promax rotation to determine latent variables was used, and McDonald's omega to verify the internal consistency of factors. Results: Factor analysis results, like other studies, showed 2 factors explaining 22 % of variance, that can be interpreted as a negative (including feelings of helplessness, apathy, boredom, emptiness, hopelessness, dysphoria) and positive attunement (happiness, satisfaction, energy). To explain at least 60% of variance, it would be necessary to use at least 6 factors, which reduces their interpretability. The individual factors had the internal consistency in the range of 0.710.74, the total internal consistency of the questionnaire was 0.75. Conclusion: The GDS-15 scale is a reliable, internationally used method for depression screening in the elderly population, whose factor structure makes it possible to capture various symptoms of depression. The limitation so far is that GDS-15 data is only available from healthy people in the Czech Republic. Therefore it is not possible to define a cutoff to determine the risk of clinical depression, for which it would be necessary to obtain adequate data from the clinical population.