The ageing of the population has negative effects on the gross domestic product (GDP), influencing various economic and social aspects. These effects, in turn, contribute to an increase in the debt-to-GDP ratio, raising concerns about the long-term sustainability of public debt. The objective of our study is to evaluate the possible dynamics of debt sustainability with a certain level of probability. The analysis employs the stochastic modelling of risk factors influencing the debt-to-GDP ratio, particularly emphasising the economic consequences of population ageing. Using advanced risk management techniques, we aim to provide a robust assessment of how future demographic outlooks impact debt sustainability.