Validation of an instrument to evaluate quality of life in the aging population: WHOQOL-AGE

Francisco Flix Caballero 0 1 2 3 4 Marta Miret 0 1 2 3 4 Mick Power 8 Somnath Chatterji 7 Beata Tobiasz-Adamczyk 6 Seppo Koskinen 5 Matilde Leonardi 10 Beatriz Olaya 0 3 9 Josep Maria Haro 0 3 9 Jos Luis Ayuso-Mateos 0 1 2 3 4 0 Instituto de Salud Carlos III, Centro de Investigacion Biomedica en Red de Salud Mental CIBERSAM , Spain 1 Department of Psychiatry, Universidad Autonoma de Madrid , Madrid , Spain 2 Department of Psychiatry, Hospital Universitario de La Princesa, Instituto de Investigacion Sanitaria Princesa (IP) , Madrid , Spain 3 Instituto de Salud Carlos III, Centro de Investigacion Biomedica en Red de Salud Mental CIBERSAM , Spain 4 Department of Psychiatry, Universidad Autonoma de Madrid , Madrid , Spain 5 National Institute for Health and Welfare , Helsinki , Finland 6 Department of Medical Sociology, Jagiellonian University Medical College , Krakow , Poland 7 Department of Health Statistics and Information Systems, World Health Organization , Geneva , Switzerland 8 Section of Clinical and Health Psychology, University of Edinburgh , Edinburgh , UK 9 Parc Sanitari Sant Joan de Deu, Universitat de Barcelona , Sant Boi de Llobregat, Barcelona , Spain 10 Fondazione IRCCS, Neurological Institute Carlo Besta , Milano , Italy Background: There is a need for short, specific instruments that assess quality of life (QOL) adequately in the older adult population. The aims of the present study were to obtain evidence on the validity of the inferences that could be drawn from an instrument to measure QOL in the aging population (people 50+ years old), and to test its psychometric properties. Methods: The instrument, WHOQOL-AGE, comprised 13 positive items, assessed on a five-point rating scale, and was administered to nationally representative samples (n = 9987) from Finland, Poland, and Spain. Cronbach's alpha was employed to assess internal consistency reliability, whereas the validity of the questionnaire was assessed by means of factor analysis, graded response model, Pearson's correlation coefficient and unpaired t-test. Normative values were calculated across countries and for different age groups. Results: The satisfactory goodness-of-fit indices confirmed that the factorial structure of WHOQOL-AGE comprises two first-order factors. Cronbach's alpha was 0.88 for factor 1, and 0.84 for factor 2. Evidence supporting a global score was found with a second-order factor model, according to the goodness-of-fit indices: CFI = 0.93, TLI = 0.91, RMSEA = 0.073. Convergent validity was estimated at r = 0.75 and adequate discriminant validity was also found. Significant differences were found between healthy individuals (74.19 13.21) and individuals with at least one chronic condition (64.29 16.29), supporting adequate known-groups validity. Conclusions: WHOQOL-AGE has shown good psychometric properties in Finland, Poland, and Spain. Therefore, considerable support is provided to using the WHOQOL-AGE to measure QOL in older adults in these countries, and to compare the QOL of older and younger adults. - Background The World Health Organization Quality of Life Assessment (WHOQOL) is an instrument to measure quality of life (QOL). It has been simultaneously developed in different cultures and languages in order to make it applicable across cultures [1]. There are some areas of QOL that may be more relevant for older adults; therefore, specific instruments that assess QOL adequately in the older adult population are needed [2]. The present study aimed to validate an instrument, the WHOQOL-AGE, built upon previous WHOQOL instruments, which is relatively short to use, e.g., in large-scale population studies or in busy clinical settings; use this instrument to measure QOL in an aging population; and test its psychometric properties in terms of its validity and reliability. Several versions of the WHOQOL instruments have been shown to have good psychometric properties in terms of reliability, validity and sensitivity to change in different population groups. WHOQOL-100 is a reliable and valid measure of QOL for use in a diverse range of cultures [1] which consists of 24 facets grouped into six domains, whereas WHOQOL-BREF is a reduced 26-item version comprising four domains: physical, psychological, social and environment [3]. The EUROHISQOL eight-item index [4] is a brief questionnaire based on WHOQOL-100 and WHOQOL-BREF. It has shown good cross-cultural performance in ten European countries, as well as satisfactory convergent and discriminant validity. In order to understand the QOL of older adults, some instruments to measure QOL in the elderly, such as the Elderly Quality of Life Index (EQOLI) [5] and the Quality of Life Scale for Elderly (QOLS-E) [6], have been developed. EQOLI was developed in Brazil to monitor longitudinal change in QOL, as well as to evaluate the impact on QOL of behavior, intervention, and treatment. The instrument comprises eight domains and 43 items [7]. The QOLS-E was developed and validated in a sample of the institutionalized population in Japan, and showed an adequate factor structure, although its reliability was not very high [6]. The WHOQOL-OLD is a supplementary module for the WHOQOL for use with older adults, developed using the WHOQOL methodology, in which a simultaneous approach to instrument development is employed in different cultures [2]. Recently, short versions of WHOQOLOLD have also been developed [8]. Since WHOQOL-OLD needs to be administered together with WHOQOL-BREF, its administration, even when using the short versions of WHOQOL-OLD, requires a long time. Consequently, there is still a need to identify a parsimonious set of items to evaluate QOL in older adults in the general population that can be administered when time is at a premium, e.g. in population-based or clinical studies when other additional data need to be collected, depending on the primary purpose of the study. WHOQOL-AGE is attempting to cover this need, since it is a short instrument, designed to be administered in general population studies, which covers the areas of QOL that are specific to older adults. WHOQOL-AGE has been designed specifically for the aging population, but in order to understand the transition of aging, it is also important to be able to compare the QOL of the aging population with younger people. The validation process of WHOQOL-AGE will, therefore, be carried out in the aging population and in the population aged 1849 years, in order to make sure that the instrument also allows comparisons with younger populations. Methods Design and procedure The Collaborative Research on Ageing in Europe (COURAGE in Europe) is an observational, crosssectional study of the general non-institutionalized adult population reached though household interviews. The sample is representative of three European countries (Finland, Poland, and Spain), which were selected to give a broad representation across different geographical European regions, tak (...truncated)