The course of the COVID-19 pandemic in Poland (2020-2023)

INTRODUCTION

The discovery of a novel coronavirus at the end of 2019 in Wuhan China heralded a new chapter in glo­bal public health. The COVID-19 pandemic has abruptly halted a continuous increase in average life expectancy observed through most of the 20^th century [1]. The pandemic deteriorated preexisting health inequalities between countries.
Poland is a country which underwent a significant socio-economic and health-related transformation in the last decades. We have observed one of the steepest increase in life expectancy after 1990. Between 1990 and 2002 life expectancy increased by 4 years among Polish men and 3 years among Polish women [2]. However, few years before the outbreak of the pandemic the increase slowed down and then life expectancy halted. COVID-19 only exacerbated the existing gap between health status in Poland and Western European countries. The report on health status of Polish population and its determinants stated that health had alarmingly deteriorated during the pandemic. Life expectancy in 2021 decreased by 2 years in comparison to 2019 [3]. In 2021 COVID-19 was the second cause of death in Poland, giving way only to cardiovascular diseases [3].
In order to analyze the course of the COVID-19 pandemic and to fully grasp its burden, it is crucial to rely on accurate measurements and objective parameters. National strategies to mitigate the effect of the pandemic have to be evidence-based. However, in many countries including Poland, there has been a varying gap between officially reported COVID-related deaths and overall mortality in the same time period [4].
In the first months of the pandemic, the metric of excess mortality has been proposed as the “golden standard” in assessing the true toll of the pandemic [5]. This metric is independent from testing coverage, adopted definition of COVID-death or quality of medical records [6]. Recently published global analysis of excess mortality in 2020-2021 indicates severe undercount of COVID deaths [7]. On the basis of excess mortality during this time period, the authors estimated that the COVID-19 pandemic has been responsible for 18,2 million deaths worldwide and not 5,94 million as officially reported [7]. Global excess mortality was higher in 2021 than in 2020 [8]. According to latest World Health Organization (WHO) estimates, Poland was among the top 20 countries with the highest excess mortality between 1^st January 2020 to 31^st December 2021 [8]. Authors state that excess mortality in these 20 countries accounted for 80% of global excess deaths until December 2021. Countries with the highest mortality counts included India, Russian Federation, Indonesia and USA [8]. Excess mortality in 2021 has been also influenced by availability and timeliness of vaccines distribution in the populations.
Poland is especially interesting country to study, as the development of the pandemic differed from western European countries [9]. Moreover, Eastern Europe has been reported to have one of the highest burden of excess mortality worldwide [7]. We have previously discussed the excess mortality in Poland in 2020 [10]. The aim of this article is to analyze the problem further, use the excess mortality as a proxy of the course of the pandemic in Poland until the mid-March of 2023, when most of the restrictions were lifted.

MATERIAL AND METHODS

This article presents the analysis of excess mortality throughout the course of the COVID-19 pandemic in Poland, that is from mid-March 2020 to mid-March 2023. We chose this period of analysis, because it captures the time between the confirmation of first cases of SARS-CoV-2 infections in Poland until the moment, when most of the restrictions related to COVID-19 were lifted. Excess mortality has been defined as a surplus in mortality from all causes in a specific period in a given population over the mortality expected based on historic data [5]. Data on number of weekly deaths from all causes, as well as number of population to calculate crude rates, were obtained from National Statistical Office [11]. Absolute number of excess deaths in Poland was calculated as a difference between number of deaths in 2020, 2021, 2022 and average number of deaths recorded in the period of 5 years (2015-2019) prior to pandemic with corresponding 95% confidence intervals. We followed the week numbers recommended by the National Statistical Office and uniform with international system laid out in the ISO8601. Data on all-cause weekly mortality has been extracted from National Statistical Office database [12].
To analyse trends of weekly excess deaths in observed period in Poland the joinpoint analysis was carried out separately for 2020, 2021 and for 2023 together with the first three weeks of 2023 using Joinpoint Regression Program (version 4.6.0.0 – April 2018, available from the Surveillance Research Program of the US National Cancer Institute [13]. Joinpoint is a model that identifies the points in a trend (joinpoints) where the linear slope of the trend changes significantly. Modelling with a maxi­mum of 5 joinpoints (corresponding to up to 6 different trends) was applied. The software computed the annual percentage change (APC) with the corresponding 95% confidence intervals. The analysis was divided into three periods: weeks 1^st-42^nd, which corresponds to period starting from 9^th March 2020 and ending on 27^th December 2020, weeks 43^rd-94^th that is the period from 4^th January 2021 to 2^nd January 2022, and weeks 95-149: from 3^rd January 2022 to 22^nd January 2023. Weeks number 150^th-156^th were excluded from the joinpoint analysis according to negative values of excess deaths. Results were gathered together and presented at Figure 2.

RESULTS

From the mid-March 2020 until mid-March 2023 we observed four visible peaks of excess mortality. No significant increase in excess mortality was observed in the first half of the year. The first surge in excess morta­lity was observed towards the end of 2020 (between 44^th and 52^nd week). A total of 76,670 excess deaths have been observed until 31^st December 2020. In the peak moment, at 45^th and 46^th week, a weekly number of excess deaths exceeded 8000 (a two-fold higher number of weekly deaths than in the historic average). The year 2021 brought two peaks of excess mortality: spring (between 5^th and 25^th week of 2021) and autumn/winter (between 36^th week of 2021 and 8^th week of 2022). A total of 117, 234 excess deaths were recorded in calendar year 2021. Two consecutive peaks in 2021 were lower than 2020 peak. The weekly number of excess deaths in 2021 both in spring and winter peaked at 5800 excess deaths. The last significant peak of excess mortality started in 49^th week of 2022 and lasted until 2^nd week of 2023. A total of 46,561 excess deaths were observed in calendar year of 2022. In 2023 excess deaths were observed only during first 3 weeks and then the number of all-cause deaths were lower than average number of deaths in years 2015-2019. Taken together, around 243 thousand excess deaths were observed in Poland from mid-March 2020 and January 2023. Absolute weekly number of deaths in 2020-2023 in comparison to average number of deaths between 2015-2019 in the Polish population is presented in Figure 1.
We can observe a visible surplus of excess mortality in men over women in 2020 and 2021. In 2022 the cumulative number of excess deaths was higher in women by 11%. Highest excess mortality was observed in older age groups (above 65 years old). Poland experienced interesting geographical distribution of excess death by sex. In 2020, two-fold higher crude rate of excess deaths in men over women aged 65+ was observed in following provinces: dolnośląskie (sex ratio of 2.1), opolskie (2.09), podkarpackie (2.05), pomorskie (1.94), zachodniopomorskie (1.97). In 2021, a notable surplus in men (over 1.5-fold) has been observed in śląskie (1.68), dolnośląskie (1.65), pomorskie (1.61), lubuskie (1.53), małopolskie (1.53). Although in 2022, crude rates of excess deaths were lower than in 2020 and 2021, still a higher mortality in men was especially prominent in świętokrzyskie (1.94), zachodniopomorskie (1.86), opolskie (1.83) and dolnośląskie (1.71).
Figure 2 presents trends of weekly excess deaths between March 2020 and January 2023 that describes the course of the COVID pandemic in Poland. Joinpoint analysis indicated thirteen periods of the pandemic. First two periods between week of 9^th-15^th March 2020 and the week of 28th September – 4^th October 2020 were characterized by slight increase of excess deaths. Then was a sharp increase and the pick of the highest number of excess deaths observed during the whole period of the pandemic (week 26^th October – 1^st November 2020). Next, there were two periods of sharp decrease in excess deaths until week of 22^nd-28^th February 2021 followed by the second abrupt increase and peak in the week of 29^th March – 4^th April 2021. Then, we observed the phase of decrease reaching almost zero excess deaths in week of 2^nd-8^th August 2021 followed by increase reaching third peak. Then we observed consecutive periods of rise and fall of excess deaths with effect of pandemic suppression with the last peak in December 2022 and the last period of decline in excess deaths in January 2023.
Figure 3 presents a total crude rates of excess deaths in men and women above 65 years of age in Poland by pro­vince per 100 000 inhabitants in 2020, 2021, 2022. There were some differences in spatial distribution of excess deaths between men and women aged 65 years and over. In men in 2020 higher crude rates of excess deaths were observed in western and some southern provinces (podkarpackie, opolskie and lubuskie provinces). On the other hand, in 2021, higher excess mortality in men moved towards the eastern and southern provinces (podlaskie, śląskie, warmińsko-mazurskie, kujawsko- pomorskie, lubelskie, lubuskie). In 2022 in men higher crude rates of excess deaths were reported in northern and western provinces (zachodniopomorskie, pomorskie, dolnośląskie). In contrary to men aged 65+, the highest crude rates of excess deaths in 2020 in women aged 65+ were observed in southern and eastern provinces (especially małopolskie, świętokrzyskie, mazowieckie, podkarpackie, warmińsko-mazurskie). Similarly to men, in 2021 higher excess mortality in women was observed in eastern Poland (lubelskie, podlaskie, podkarpackie, warmińsko- mazurskie). In 2022, in women highest excess mortality was observed in northern and western provinces (pomorskie, kujawsko-pomorskie, warmińsko-mazurskie, dolnośląskie, zachodnio-pomorskie).

DISCUSSION

This article presents analysis of excess mortality recorded in Poland between mid-March 2020 and mid-March 2023. Overall, in 2020-2023 more than 240 000 excess deaths have been recorded in Poland, which is one of the highest mortality in Europe. We observed three peaks of excess deaths during this time of observation. The first one happened at the end of 2020 (between 44^th and 52^nd week) and it was the most severe. Excess mortality in 2020 has been separately described by us in the previous paper [10]. However, excess mortality hasn’t stopped in 2020. In 2021 and in the beginning of 2022 we observed three peaks of deaths, which combined exceeded the size of the 2020 peak.
Excess mortality is considered a golden standard in assessing the impact of the pandemic, because it is independent from testing coverage and death reporting practices, which vary between countries. Pizzato et al. [15] estimated that number of excess deaths in Europe between 2020 and 2023 reached over 1.6 million, with big disparities observed between European countries, which might have reflected the differences in socio- economic status, population’s health status prior to pandemic and public health actions. In the same paper, Poland was surpassed only by Italy in absolute number of excess deaths, and by Bulgaria, Lithuania, Slovakia and Latvia in number of age-standardized excess deaths [15] among all European countries. Central and Eastern European countries were characterized by higher burden of all-cause mortality during the pandemic. In Western European countries, e.g. in Norway, excess mortality, albeit present, was mostly attributed to increased non-COVID mortality [16]. Raknes et al. [16] reported excess cardiovascular mortality by 14.3% in 2021 and 22.0% in 2022 and excess mortality due to neoplasms in 2022 by 3.5%. Interestingly, mortality was lower for respiratory diseases in the same period of time [16]. Authors specu­lated on several explanations: that some deaths caused by COVID might have been misreported; COVID infection in short or long term might have contributed to increased cardiovascular and oncological mortality and lastly increased non-COVID mortality might have been caused by impaired access to healthcare or the fact that some patients might have been reluctant to participate in screening due to fear of infection [16]. A rank-list of excess mortality in the European countries based on analysis by Pizzato et al. [15] is summarized in Figure 4.
It is not possible to determine exact causes of deaths only on the basis of overall excess mortality. This metric combines deaths both directly and indirectly impacted by the pandemic. However, considering temporal trends in excess mortality in Poland, we hypothesize that the majority of excess deaths could have been attributed directly to COVID-19, since peaks in excess deaths matched peaks in Sars-Cov-2 infections with time-lag previously described in literature [17]. Other authors, who analyzed excess mortality in Poland also attributed majority of excess deaths directly to COVID-19, especially in the older age groups [4].
In the whole EU, excess mortality was 26% higher than officially reported COVID deaths [18]. However, among EU countries the highest discrepancy between excess mortality and officially reported COVID deaths was reported in Bulgaria, Romania and Poland. According to OECD report, number of excess deaths in Poland was almost twice higher than officially reported COVID deaths (as expressed per million population) [18]. Poland has been flagged as one of the European countries with biggest inconsistencies between COVID mortality and excess mortality [19]. This discrepancy may be attributed to low testing coverage in Poland. Number of performed tests were one of the lowest in Europe in 2020 [10], which didn’t improve much in 2021. Since the beginning of the pandemic until April 2022, the cumulative total number of tests in Poland equaled 950/1000 people. This number was 2-times lower than in Netherlands, 5-times lower than in Czech Republic, 7-times lower than in United Kingdom and over 11-times lower than in Denmark [20]. It is reasonable to assume that a significant number of infections were undetected and underreported.
Excess mortality tends to be significantly lower in countries with higher life expectancy prior to COVID-19 pandemic, higher GDP per capita and higher vaccination rate [21]. Similarly, the meta-analysis by Hajdu et al. [22] found a strong negative association between pre-pandemic regional life expectancy and excess mortality rate over the course of the pandemic. In Europe a pre-pandemic life expectancy lower by one year was associated with the average of 521 more excess deaths per million inhabitants [22]. High rates of excess morta­lity in Poland during COVID-19 pandemic can be symptomatic of ongoing health deterioration, which started before the pandemic. Life expectancy ceased to improve in Poland in 2014 in men and 2016 in women [23]. Many factors present in the pre-pandemic time, including access to healthcare, prevalence of modifiable risk factors including tobacco smoking, alcohol consumption, obesity, lifestyle-related factors likely contributed to higher mortality during the pandemic. Significant increase in alcohol-related deaths in Poland, among other factors, likely contributed to cessation of improvement in life expectancy before the COVID-19 pandemic [23]. Moreover, alcohol-related death rates deteriorated also during the first years of the pandemic [24]. During the pandemic, the life expectancy decreased in Poland by two years both in men and women, and returned to pre-pandemic level in 2023 (74 years for men and 82 years for women) (trends in life expectancy in Poland between 1960 and 2023 are presented in Supplementary Figure 1). This phenomenon was observed in case of other historical events characterized by excess mortality, e.g. epidemic of the Spanish flu. Temporary decrease in life expectancy during the COVID-19 pandemic was observed in the whole Europe, however the current average life expectancy in EU not only returned to the pre-pandemic level, but exceeded the life expectancy in 2019 [25].
We observed some spatial differences in excess mortality in Poland. Higher rates of excess mortality were observed in provinces generally characterized by lower average life expectancy prior to the pandemic in 2019 [26], which is consistent with the literature. In 2021 and 2022 the spatial distribution of excess mortality for men and women was comparable. However, at the beginning of the pandemic in 2020, higher crude rates of excess deaths in men were observed in southern/western Poland, whereas in women in southern/eastern provinces (with the exception of lubuskie province). Although Italy and Poland had comparable volume of excess mortality, a more significant spatial sub-national variation has been observed in Italy (with highest mortality reported in northern part of the country) [27]. In both men and women, highest losses in life expectancy in 2020 were observed in southern-eastern provinces in Poland, and for men additionally in the northern provinces [27].
Ecological analysis performed in 178 countries by Mendoza-Cano et al. [28] suggested a significant association between higher vaccination coverage and lower overall mortality. Similar conclusion was made in a paper by Hoxha et al. [29], the analysis showed that a 10% increase in vaccination was associated with an 18.1% decrease in mortality after 6 months and a 16.8% decrease after 12 months. By September 27th 2023, 57.4% of the Polish population received at least one dose of vaccine, which was lower vaccination coverage in comparison to western EU countries [30]. On average in the EU, 75.1% of population received at least one dose of vaccine, 77.8% of po­pulation in Germany, 66.5% in Czech Re­public, 79.7% in the United Kingdom, 80.8% in Den­mark [30].
This analysis has some limitations to consider. Using weekly mortality from 2015-2019 as a baseline might has contributed to slight overestimation of excess mortality in 2020-2023, since mortality rates in Poland are increasing over time. Despite this limitation, the analysis of excess mortality is still one of the most reliable tools to analyze the course of the pandemic.

CONCLUSIONS

The magnitude of excess mortality during the COVID-19 pandemic in Poland was catastrophic. Poland was one of the countries with the highest excess mortality in Europe between 2020 and 2023. The first wave of excess deaths at the end of 2020, was concomitantly the highest. Two subsequent peaks of excess deaths in spring and winter 2021 were of similar magnitude and lower than the previous one. The last and the lowest peak of excess deaths was observed in winter 2022/2023. The discrepancy between excess mortality and officially reported COVID-19 deaths suggests severe undercount of the latter. Excess mortality can be symptomatic of ongoing health crisis in Poland, which started prior to the pandemic.

FUNDING

ABR and KZ collaborated in preparing the article within the framework of the topic “Assessment of the prevalence of risk factors for noncommunicable and infectious diseases with special emphasis on behavioral, socio-economic and environmental factors among Lower Silesian children and adults” task recorded in the SIMPLE system: SUBZ.E290.25.009.

DISCLOSURE

The authors report no conflict of interest.

References