Validation of the German Purpose in Life Questionnaire (PLQ) in a healthy population and patients with cardiovascular disease

In this cross-sectional study, a German translation of the subscale "Purpose in Life" (PLQ) from the Scales of Psychological Well-being (SPWB) was validated in a representative sample of participants from healthy and cardiovascular populations. The main objectives were to assess the reliability, convergent, and discriminant validity using a large and representative sample (N = 466 healthy sample, N = 247 patients with an implanted cardioverter-defibrillator (ICD), N = 70 patients with a cardiovascular disease (CVD)). The findings indicated that the German PLQ is a reliable and valid measure of positive psychological well-being, showing a positive correlation with health-related quality of life, optimism, and positive affect. In turn, the PLQ score was significantly and negatively correlated with depressive symptom severity, anxiety, pessimism, and negative affect, while being distinct from these constructs. The comparability of the measurement properties of the German PLQ with the original English version further supports the validity of the translation. Additionally, the unidimensional structure of the German version mirrored that of the English PLQ. As this study used a large and representative sample, it provides the most up-to-date normative population value for the subscale of the SPWB. Moreover, this study represents the first known exploration of the questionnaire in a cardiovascular sample, revealing relationships between health-related quality of life, optimism, positive affect, and the German PLQ. However, in patients with ICD, the positive correlation between the PLQ and the physical component of the SF-12 did not reach significance. Despite these valuable findings, future research to enhance the understanding of the PLQ and its implications is warranted.