<p>While many existing studies are country-specific or rely on simple regression methods, this study aims to explore how socio-demographic, mental, and government factors (three of the most critical dimensions influencing quality of life) play differential roles across 35 countries. Also, whereas previous research tends to focus on only one of these domains, this study integrates all three using Hierarchical Linear Regression. This study finds that mental factors consistently have a negative effect on all categories of quality of life. For instance, isolation negatively impacts happiness, ease of life, and life satisfaction. Moreover, mental factors exert the strongest influence compared to the other domains: lacking shows the highest negative impact on happiness, followed by isolation and alone. Government factors also show category-specific effects. For example, healthcare positively contributes to happiness and ease of life, while policies for the elderly enhance life satisfaction. Lastly, most socio-demographic factors significantly relate to all quality of life categories, with all, five, and six out of eight factors significantly associated with happiness, ease of life, and life satisfaction, respectively.</p>