Temperature-attributable mortality projections under scenarios of climate change for Oslo, Norway

Climate change and evolving of population dynamics, including ageing and changes in population size, are reshaping temperature-attributable mortality patterns. However, there is limited evidence on the prospective trajectory of heat- and cold-attributable mortality in Oslo, particularly under combined scenarios of global warming and population development. This study aims to project heat- and cold-attributable mortality in Oslo and assess the distinct contributions of each of these drivers, utilising high-resolution data. We conducted a two-step approach with time series analysis with distributed lag non-linear models to estimate heat- and cold-attributable mortality relationship based on mean daily ambient temperature. Then, we performed a health impact assessment to compute the attributable mortality to heat and cold in the baseline period (2010–2019) and by the end of the century using regional population projections, mortality rates and projected daily temperature under two climate scenarios: RCP4.5 and RCP8.5. For the RCP4.5/Medium Road scenario, the attributable mortality fractions for heat and cold are projected to increase over time, with values ranging from 9.05% (95%CI: 1.55–15.90) in 2010–2019 to 9.78% (95% CI: 2.96–15.86) in 2090–2099. Cold mortality consistently dominates the total, while heat mortality remains relatively low, starting at 1.80% (95%CI: 0.10–3.68) at baseline and increasing slightly to 3.12% (95%CI: 0.34–5.94) by the end of the century. In contrast, the RCP8.5/Strong Ageing scenario shows a more pronounced rise, with temperature-attributable mortality increasing from 9.07% (95%CI: 1.53–15.89) in 2010–2019 to 11.86% (95%CI: 4.29–18.53) in 2090–2099. In this scenario, heat mortality contributes significantly more, rising from 1.83% (95%CI: 0.12–3.85) in 2010–2019 to 5.99% (95%CI: 1.23–10.35) by 2090–2099, reflecting the greater climate and population impact under RCP8.5 and the Strong Ageing pathway. Our findings highlight the need for climate and population dynamics to be considered in public health policies. Tailored interventions are crucial to mitigate heat and cold-attributable mortality, particularly for vulnerable populations. Future research should integrate socio-economic factors and explore adaptation strategies to refine mortality projections and inform policy.