Psychometric properties of the World Health Organization Quality of Life 100 questionnaire in the middle-aged Lithuanian population of Kaunas city

Abstract

This study aimed to identify psychometric properties of the World Health Organization Quality of Life 100 questionnaire. Material and methods. A random sample of 1403 Kaunas city men and women aged 35-64 years was examined in 2001-2002. Quality of life was assessed by the self-administered World Health Organization Quality of Life 100 questionnaire. Statistics. Scores of all domains and facets of the questionnaire were transformed to reflect a scale from 0 to 100. The validity and reliability of the questionnaire were evaluated by Pearson's correlation coefficients and by Cronbach's α. The relationship between the WHOQOL-100 domains and the two general items (G1 and G4) was assessed using linear regression analysis. Exploratory factor analysis was conducted to explore the factor structure of the data. Results. The mean scores of the World Health Organization Quality of Life 100 questionnaire domains ranged from 51.3±15.1 (overall quality of life) to 72.0±16.4 (level of independence domain). The instrument displayed acceptable Cronbach's α (0.77-0.91) and test-retest reliability (0.64-0.89). The overall assessment of quality of life (G1) was most strongly associated with the environment (β=0.31), psychological (β=0.18), and social relationships (β=0.17) domains. Overall health (G4) showed the strongest association with the level of independence (β=0.34) and physical (β=0.18) domains. The principal component analysis revealed five-factor solution, which accounted for 57.7% of a total variance. Conclusion. In the Lithuanian population, the World Health Organization Quality of Life 100 questionnaire was found to be a suitable instrument for evaluating quality of life.