Multiple causes of death data to track trends of mortality from chronic diseases: Insights from the COVID-19 pandemic in Switzerland

PURPOSE: With the rising prevalence of multi-morbidity among aging populations and disruptive events as new infectious disease threats, the traditional focus on the underlying cause of death (UCOD) can obscure the contribution of chronic diseases to mortality trends. The multiple cause of death (MCOD) approach addresses this limitation by considering all causes recorded on a death certificate. We aimed to quantify the effect of the COVID-19 pandemic on trends of chronic disease mortality by comparing the UCOD and MCOD approaches. METHODS: We conducted a population-based time series analysis using all deaths occurred 2011-2022 in Switzerland. We modelled pre-pandemic (2011-2019) trends to predict the expected chronic disease deaths during 2020-2022 had the pandemic not occurred. We quantified the monthly effect of the pandemic as the observed minus expected chronic disease deaths and estimated these effects by sex and age using (1) the UCOD and (2) the MCOD. RESULTS: Both approaches revealed similar overall trends of effects. However, a marked discrepancy occurred at the end of 2020, when Switzerland experienced the highest COVID-19 mortality, with MCOD quantifying a substantially higher excess of chronic disease deaths compared to UCOD. CONCLUSION: MCOD complements UCOD in quantifying cause-specific mortality trends and may improve population health monitoring.