Validating the Polish Adaptation of the 11-Item De Jong Gierveld Loneliness Scale

The aim of this study was to translate into Polish and establish the psychometric properties of the 11-item De Jong Gierveld Loneliness Scale (DJGLS). The translation process followed the recent guidelines for the crosscultural adaptation of questionnaires and was tested through analysis of differential item functioning (DIF) by the use of the Poly-SIBTEST method and bilingual groups. The essential unidimensionality was checked by bifactor analysis. Reliability was assessed by internal consistency and homogeneity analysis, and external construct validity by correlation with several external scales. The research indicated no differences in item performance between the final Polish and English versions, and confirmed the earlier findings indicating that the DJGLS measures two dimensions of loneliness (social and emotional) which generalize into a higher-order factor of a general sense of loneliness (bifactor structure). Reliability (alpha = .89) and homogeneity (H = .47) proved to be high. Research showed that the instrument has a satisfactory validity criterion: Correlation with the UCLA Loneliness Scale r = .82; with Rosenberg's Self-Esteem Scale r = -.56; and with the Beck Depression Inventory r = .46 (all p < .01). The Polish adaptation of the DJGLS thus presents a bifactor structure, with good levels of internal consistency, homogeneity, and construct validity.