COVID-19 disrupted patterns of cause-specific mortality in Switzerland

To understand disruptions in mortality patterns during the COVID-19 pandemic beyond deaths directly attributed to SARS-CoV-2.

We analysed Swiss weekly deaths (2011-2021) by age, sex, region, and nine cause groups. For each age group, a Bayesian multivariate Poisson model was fitted to 2011-2019 data, accounting for seasonality, long-term trends, and cross-cause dependence. Comparing predictions with 2020-2021 observations revealed age- and cause-specific excesses.

Cardiovascular deaths peaked during the autumn 2020 wave, while no cause showed sustained excess across 2020-2021. In individuals aged ≥80 years, non-COVID respiratory (-25%) and mental/neurological (-12%) deaths declined, largely offset by COVID-19 deaths, leaving a modest +4.5% all-cause excess. Cardiovascular and mental/neurological excesses correlated with COVID-19 and other respiratory excesses, reflecting strong pre-pandemic cross-cause correlations ( $\rho >0.80$ ).

These patterns likely reflect three overlapping mechanisms: reduced circulation of non-COVID-19 respiratory pathogens, unrecognized COVID-19 deaths (especially cardiovascular), and mortality displacement, pointing to possible underestimation of the true respiratory burden.