Coherence of COVID-19 Mortality of Spain Versus Western European Countries

Abstract

The mortality impact of COVID-19 across European countries is a complex phenomenon that appears to be influenced by political, social, economic, and environmental factors. The western European countries have implemented similar policies, with some specific minor divergences, like in the implementations of lockdowns and vaccination passes, so that similar results were to be expected. We use the wavelet transform coherence (WCT) in order to assess the correlation at diverse time scales among COVID-19 mortality time series. The same process was carried out over the time series of stringency index of implemented population control polices. Specifically, we consider the pairwise WCTs of the COVID mortality and the stringency time series of western European countries versus Spain. We discuss the findings on the WCT plots regarding the temporal inhomogeneity of the plots, and the lack of correspondence between WCT plot dissimilarity and geographical distance of countries relative to Spain. This discussion raises questions about the hypothesis of the transmission of a specific pathogen as the main mechanism underlying the mortality attributed to COVID-19. The synchronization of non-pharmaceutical interventions in the first epoch is highly correlated to the synchronization of the mortality waves in almost countries. As an indication of the impact of political measures on COVID-19 mortality, we compute the overall correlation between second order correlation between mortality time series and stringency index time series, finding a highly significant positive correlation (0.53, $p<<0.05$), raising the question if stronger political measures may have lead to increased COVID-19 mortality.