The objective of this study was to quantify and describe the changes in the mortality in Estonia during the period of the Covid-19 pandemic (years 2020 and 2021) in terms of excess mortality and the distribution of causes of death.
According to the study results, there was no excess mortality in 2020; however, significant excess mortality occurred in 2021. These findings may be attributed to the fact that in 2020, the spread of the virus was not as extensive as in 2021. While the highest seven-day average number of infections remained around 550 in Estonia in 2020, it rose to 1940 in 2021 (20). The more limited spread of the virus in 2020 could have resulted from stricter restrictions and the state of emergency declared in the Republic of Estonia (20, 21). Additionally, in 2021, the dominant SARS-CoV-2 virus variants, alpha and delta, were more virulent compared to the original Wuhan variant that dominated in 2020 (22). The results obtained in this study are consistent with previous studies conducted in Estonia in 2020, which did not identify significant excess mortality either (23, 24). The findings of the study also align with research analyzing changes in average life expectancy, which found that there were no changes in average life expectancy in Estonia in 2020, but in 2021, there was a statistically significant decrease (25, 26).
Upon closer analysis of excess mortality, looking at different age groups, it was found that the excess mortality observed in 2021 was due to an increase in mortality in the age group ≥ 55 years. Similarly, in a study analyzing changes in the population's average life expectancy in Estonia, it was found that the main cause of the significant decrease in average life expectancy in 2021 was excess mortality in the age group ≥ 60 years (25). Since older age is one of the risk factors for Covid-19, it explains the occurrence of excess mortality in the oldest age group. According to the results of this study, excess mortality was also observed in men aged 35–54 in 2021. The slightly increased mortality among men aged 35–54 may be attributed to their increased likelihood of developing severe cases of Covid-19. Compared to women, men have a higher chance of developing severe forms of Covid-19. (27)
While statistically significant joinpoints in mortality rate trends did not precisely align with the Covid-19 pandemic period, mortality rates increased significantly for both men aged 35–54 and women aged ≥ 55 during the study period. The joinpoint in the upward trend in mortality rate for men aged 35–54 occurred in February 2019, with a magnitude of change of 0.7% by the end of the study period. For women aged ≥ 55, the inflection point in mortality rate trends occurred from July 2018 until the end of the study period, with a monthly percentage change in mortality rates of 0.6%. It is challenging to pinpoint the reasons why these specific joinpoints occurred at these particular times and what caused the transition from a declining trend to an increasing trend. However, the increase in mortality rates persisted throughout the entire period of the studied pandemic. The joinpoint regression curve of mortality rates for men aged ≥ 55 showed a 9.5% increase from September 2020 to December 2020, which was not statistically significant. Meanwhile, Estonia experienced the surge of the second wave of the Covid-19 pandemic, with the alpha variant (also known as the British variant) starting to spread. The number of new cases continued to rise during the second wave of the pandemic until March 2021. (20, 28) However, starting from December 2020, the regression line for men aged ≥ 55 declined by -0.6%. The − 0.6% decrease in the regression line was not statistically significant, and even after the decline, the mortality rate for men aged ≥ 55 remained higher than that of women in the same age group. Covid-19 vaccination began in Estonia in January 2021. It is possible that the decline in mortality rate trends among men aged ≥ 55 was caused by vaccination (29). However, a similar decline in mortality rate trends for women in the same age group, aged ≥ 55, was not observed. There is a higher prevalence of multimorbidity among women in Estonia, indicating the concurrent presence of multiple chronic diseases (30). Therefore, women in the oldest age group had a higher risk of dying from Covid-19 compared to men in the same age group.
In the analysis of age- and gender-adjusted mortality rate ratios based on causes of death, several significant differences between reference period were identified. Consistent with the findings of several other studies, this study revealed that mortality from circulatory system diseases was higher during the pandemic period (16–19, 31). In 2021, mortality from cardiovascular diseases was 1.06 times higher (95% CI 1.03–1.09) than in 2018–2019. The increased mortality from cardiovascular diseases may be attributed to individuals with cardiovascular diseases being in the Covid-19 risk group, as well as to the heightened risk of developing cardiovascular diseases after Covid-19 infection. However, it has been observed that among individuals infected with Covid-19, in addition to the elevated risk of developing cardiovascular diseases post-virus infection compared to non-infected individuals, there is also a heightened risk of developing tumors, respiratory diseases, and other fatal conditions. (9, 14) Nevertheless, the results of this study indicated that mortality rates from tumors were significantly lower in both pandemic years, and the mortality rate from respiratory diseases in 2020 was significantly lower than in the reference period. The lower mortality rate from tumors may have been due to Covid-19 competing as a cause of death - individuals with weakened immune systems due to tumors died from Covid-19 before the tumor disease could cause death itself. The decrease in the mortality rate from respiratory diseases could be attributed to measures implemented to prevent the spread of Covid-19, such as social distancing, wearing masks, disinfecting shared surfaces, more frequent hand hygiene, and consequently a reduced risk of infection with other respiratory infectious diseases, such as influenza and pneumonia.
In 2021, the mortality rate for mental and behavioral disorders was significantly higher than in the reference period (IRR 1.42; 95% CI 1.19–1.68). The pandemic may have had a negative impact on people's mental health through their own or their loved ones' illness or increased risk of illness (contracting Covid-19), as well as due to changes in lifestyle and economic circumstances resulting from the pandemic, such as reduced socialization, changes in workload and income, job loss, and uncertainty about the future. (32). A study conducted during the first wave of the pandemic in Estonia among individuals aged 18–79 revealed that more than half (52.2%) of the study sample reported higher stress levels due to the pandemic (33). Additionally, findings from the Estonian population's mental health survey showed that the proportion of individuals surpassing the risk threshold for depression and anxiety, based on the Emotional Self-rating Questionnaire (version 2), increased in the population up to 74 years old, and the risk of depression and anxiety disorders was significantly higher in 2021 and 2022 than in 2019 (32). Furthermore, studies have found that psychiatric symptoms in individuals with pre-existing psychiatric disorders may worsen in relation to contracting the virus (34)
Individuals diagnosed with depression are more likely to consume higher amounts of alcohol compared to those without a depression diagnosis. Additionally, increased levels of stress may influence individuals to consume more alcohol. (32) The number of deaths directly attributable to alcohol-related illnesses reached its highest point in the past 13 years in 2021 (695 deaths), and in 2021, the average Estonian adult (aged ≥ 15) consumed 2.3% more absolute alcohol than in 2020 (35, 36). Therefore, mortality rates for mental and behavioral disorders, as well as for accidents, poisoning, and injuries, may have increased due to the rise in alcohol consumption. Mortality rates attributed to external causes (accidents, poisonings, and injuries) were higher in Estonia in both pandemic years compared to the reference period.
Some of the excess deaths may have been caused by the overwhelmed healthcare system and delayed medical care due to the pandemic. As a result of the Covid-19 pandemic, the delivery of many healthcare services has been postponed, and waiting lists for numerous specialties grew longer (37). For instance, at Tartu University Hospital, planned inpatient treatment was temporarily halted from 25.10.2021 due to the increased demand for Covid-19 hospitalization (38). It is also plausible that individuals refrained from seeking medical assistance for health issues out of fear of overburdening the already overloaded healthcare system or contracting the virus. Consequently, their own health problems may have been underestimated, which turned out to be more serious than expected. The effects of postponed treatment are still emerging (37). This issue is important and requires further investigation.
The spread of Covid-19 was a significant problem in many nursing homes. However, nursing home residents belong to the Covid-19 risk group and are particularly vulnerable to the dangers associated with infection. During the first wave of Covid-19, in many countries, over half of the Covid-19 deaths occurred among nursing home residents (39). Older adults are more likely to have various chronic diseases that may worsen and result in death if they contract the virus. This could have contributed to the increase in mortality rates for several diseases during the pandemic period. In addition to the aforementioned causes of death that emerged during the pandemic period, mortality from nervous system and sensory organ diseases, as well as digestive system diseases, may have also increased due to the spread of the virus in nursing homes and among the older adult population in general.
The strength of the study lies in the completeness/high quality of the data under analysis and the opportunity to use nationwide data. According to the World Health Organization (WHO). The data from the Estonian Causes of Death Registry is 100% complete. and their usability score is high. ranging from 91 to 95% (the assessment is based on data from the Causes of Death Registry from 1998 to 2019) (40). However. due to the Covid-19 pandemic as an extraordinary event. there may have been some inaccuracies in the registration of causes of death. especially in defining deaths attributed to Covid-19. and this could have influenced the results of this study to some extent. It is possible that the role of Covid-19 as a cause of death was either overestimated or underestimated during the completion of death certificates. While the Causes of Death Registry data is checked. and corrections are made by specialists as needed, following WHO guidelines. there is still room for medical professionals to exercise discretion in completing certificates and determining causes of death. Additionally. there may have been cases where Covid-19 went undiagnosed or was not recorded on the death certificate. Therefore. due to these aforementioned factors. the mortality rate ratios and distributions of underlying causes of death found in this study. may differ from reality. being either higher or lower.