In recent years, the world has witnessed a notable phenomenon: a simultaneous increase in global life expectancy and a sharp decline in birth rates. This situation presents a significant challenge for governments everywhere. It threatens the sustainability of state-funded welfare programmes like social security and suggests a potential future decrease in the workforce and tax revenue, which includes contributions to social benefits. With these issues expected to intensify over the next few decades, it is essential to thoroughly examine the implications of extended human lifespans to understand the full scope of the problem. Recent research has explored using stochastic differential equations to effectively model the dynamic nature of mortality rates. These models offer advantages over deterministic models because they incorporate stochastic variations in the environment, providing a more comprehensive understanding of the uncertainties in future predictions. Our study aims to fit and compare two types of stochastic differential equations models for mortality – the Vasicek model and the Cox-Ingersoll-Ross model. This approach will help us predict Portugal’s mortality rates through 2030. The findings are promising, as both models successfully replicate the trend of decreasing mortality rates and offer plausible forecasts for the future.