Assessing loneliness in later life: validation of the De Jong Gierveld Loneliness Scale for Portuguese older adults.

Assessing loneliness is essential to better understand older adults' mental health needs and to inform timely and appropriate interventions. The De Jong Gierveld Loneliness Scale (DJGLS) is one of the most widely used measures of loneliness worldwide. However, there is no evidence regarding its psychometric adequacy for older adults in Portugal. This study analysed the psychometric properties (validity and reliability) of the Portuguese version of the DJGLS (both the 11-item and 6-item versions) for community-dwelling older adults. A cross-sectional study was conducted with 466 participants. Construct, convergent and divergent validity were evaluated, and test-retest reliability was assessed using intraclass correlation coefficients (ICC) and Bland-Altman plots. The 11-item DJGLS showed a bifactor structure with a general loneliness factor and two specific factors (social and emotional loneliness), with good model fi, whereas the 6-item DJGLS demonstrated excellent fit. Both versions showed a significant correlation with ULCA-16 (r ≥ 0.6), adequate internal consistency (Cronbach's alpha = 0.8 (11 item) and 0.67 (6 item)), excellent test-retest (two-weeks) reliability (ICC ≥ 0.9) and acceptable agreement on the Bland-Altman plots, without evidence of proportional biases. The Portuguese versions of the DJGLS-11 and DJGLS-6 are valid and reliable instruments for assessing loneliness in Portuguese community-dwelling older adults, supporting their use in research and screening contexts. The validated version of the DJGLS enable the assessment of social and emotional loneliness, expanding the range of loneliness measures currently available in Portugal.