Measuring Subjective Vitality and Depletion in Older People from a Self-Determination Theory Perspective: A Dual Country Study.

As the global older population grows, research increasingly focuses on their well-being and quality of life, aspects that are often impacted by a perceived loss of energy and fatigue. To describe individuals' energy dynamics, Self-Determination Theory (SDT) has recently proposed a dual-process model based on two constructs: Subjective Vitality and Depletion. The present study aims to validate the Subjective Vitality/Depletion Scale (SVDS), an instrument based on this model. A sample of 726 older adults (over 65) from two countries, USA and Italy (M_age = 72.57, SD_age = 6.49), completed the SVDS, the Big Five Inventory 2 - Extra Short Form (BFI-2-XS), the 12-item Short-Form Health Survey (SF-12), and the Godin-Shephard Leisure-Time Physical Activity Questionnaire (GSLTPAQ). Confirmatory factor analyses of the SVDS support the SDT hypothesis that Subjective Vitality and Depletion are two distinct, yet related constructs. Full measurement invariance for the scale was achieved across gender and age subgroups, while partial scalar invariance was established across different countries, suggesting some specific influence of cultural factors. Correlations with BFI-2-XS, SF-12, and GSLTPAQ support the SVDS validity. The study provided evidence that the SVDS based on SDT is a valid and reliable instrument for assessing Subjective Vitality and Depletion among older individuals.