2. The impact of the COVID-19 pandemic on mortality

Differences across ages

The mortality risk from COVID-19 increases exponentially with age, similarly to the normal mortality pattern observed across ages. The Gompertz model, which is commonly used to define mortality rates across ages and assumes that mortality increases exponentially with age, provides an adequate fit for the mortality from COVID-19. Indeed, the pattern of the mortality risk from COVID-19 follows a similar pattern as that for other causes of death related to ageing, including pneumonia and influenza. However, the relative mortality risk for adults from COVID-19 is much higher, at between 2.8 to 8.2 times higher than pneumonia and influenza (Sasson, 2021[9]).

Given the exponential pattern of mortality risk across ages, the age structure of a population is clearly a determinant in the overall mortality for COVID-19 experienced in any given jurisdiction. However, the starting point of mortality also matters. Older people are at higher relative risk in high-income countries, who have lower baseline mortality at adult ages, than in low and middle-income countries. This is because high-income countries have experienced more significant longevity gains at younger to middle ages, so the mortality curve for high-income countries is much steeper (see Figure ‎2.6 for an illustration). This means that individuals ‘age’ more quickly than in low and middle-income countries where the mortality curve is flatter. As such, the mortality risk from COVID-19 increases on average by 12.6% with each year of age in high-income countries, compared to only 7.1% in low and middle-income countries (Demombynes, 2020[10]). Younger individuals in the latter countries are therefore at higher relative risk of dying from COVID-19.

Figure 2.6. Illustration of slope of mortality curves for higher and lower income countries

Differences between genders

Males are on average at a higher risk of dying from COVID-19 than females. Males represent slightly less than half of confirmed positive cases – though they are also less likely to get tested – but make up a higher proportion of confirmed deaths (The Sex, Gender, and COVID-19 Project, 2021[11]). Figure ‎2.7 shows that this is generally true in a sample of 30 OECD countries where sex-disaggregated data is available. While men represented on average 48.3% of confirmed COVID-19 cases, weighted by the number of cases, they made up 55% of the deaths (The Sex, Gender, and COVID-19 Project, 2021[11]).

Figure 2.7. Percent of male confirmed COVID-19 cases and deaths in OECD countries

Note: Data from 30 OECD countries available as of 24 August 2021.

Source: Adapted from The Sex, Gender, and COVID-19 Project (2021[11]), The COVID-19 Sex-Disaggregated Data Tracker, https://globalhealth5050.org/the-sex-gender-and-COVID-19-project/the-data-tracker.

Nevertheless, the difference between genders of mortality risk from COVID-19 are largely in line with differences in baseline mortality. One global study concluded that males were nearly 40% more likely to die of COVID-19 than females, and nearly three times more likely to require intensive care, even though there was no difference between genders with respect to the proportion of confirmed positive cases of COVID-19 (Peckham et al., 2020[12]). A study on European data estimated the increased risk of males to range from 11% to 54% (Ahrenfeldt et al., 2020[13]). Another estimate based on a review of existing studies, however, puts the relative risk to males higher at 86% (Biswas et al., 2020[14]). Nevertheless, these observations are mostly in line with the generally observed increased risk of mortality of males. To put this into perspective, males in the United States between the ages 55 and 80 have a higher risk of mortality than females between around 35% and 70%.4 Differences between genders by age also demonstrate a pattern consistent with baseline mortality, tending to increase until ages in the 60s and decreasing thereafter (Ahrenfeldt et al., 2020[13]).

There are some exceptions, however, with a handful of countries experiencing a higher case fatality rate for females. In India, for example, the case fatality rate at the end of September 2020, was 3.3% for women compared to 2.9% for men. Nepal, Slovenia, and Vietnam have also demonstrated higher case fatality rates for females. Nevertheless, it is difficult to determine whether these are the true differences in mortality or whether they may be caused by biases in reporting, testing or access to health care (Dehingia and Raj, 2021[15]).

Differences by underlying health conditions

Having an underlying comorbidity significantly increases the mortality risk of COVID-19. Kidney disease is among the most deadly, increasing the risk of death by nearly five times. Other comorbidities identified as significant risk factors include, in order of descending risk, cardiovascular disease (~3x), respiratory disease (2-3x), diabetes (~2x), hypertension (~2x), dementia (~2x), cancer (~2x), and liver disease (1.5x) (Biswas et al., 2020[14]; Cho, Yoon and Lee, 2021[16]).

Indeed, the vast majority of people who die from COVID-19 have at least one comorbidity, and multiple comorbidities are common. Among those who died of COVID-19 in Canada, for example, 90% had at least one other underlying condition, nearly two-thirds had at least two comorbidities and nearly half had three or more (Statistics Canada, 2021[17]). One study on a care home in Sweden showed that deaths during the first wave of the pandemic were mainly the frailest of the population having multiple comorbidities, with 92% of deaths having three or more comorbidities (Nilsson, Andersson and Sjödahl, 2021[18]).

Death among the population under 65 with no comorbidities remains rare. Less than 3.6% of COVID-19 fatalities under age 65 in France, Italy, the Netherlands, Sweden, Georgia (USA), and New York City (USA) had no comorbidities, though Mexico presents an exception to this with nearly 18% of those dying under 65 having no comorbidity (Ioannidis, Axfors and Contopoulos-Ioannidis, 2020[19]). However, this could be at least partially driven by lower levels of reporting or diagnosis of comorbidities in Mexico.

Frail populations are clearly more at risk of dying from COVID-19. This leads to the somewhat counterintuitive observation that countries having better health care systems also have higher COVID-19 death rates. This is because in these countries people are more likely to survive life-threatening events such as heart attacks and strokes, making the overall population frailer on average. One study found that for every 1% increase in the size of a country’s population surviving heart conditions or stroke, the death rate from COVID-19 increased by 19% (Botly et al., 2020[20]).

That frailer populations are more at risk supports the hypothesis that many of the deaths from COVID-19 are accelerated deaths that may well have occurred in the short term regardless. This phenomenon has been observed in past pandemics as well. Following the Spanish Flu of 1918-1919, the gap in life expectancy between males and females significantly decreased. This is likely because many of those dying during that pandemic also had tuberculosis. Indeed, tuberculosis rates dropped in the years following the Spanish Flu, and disproportionately so for males (Noymer and Garenne, 2000[21]).

Differences by socio-economic status

There is mixed evidence as to whether more disadvantaged groups are at higher risk of dying from COVID-19. The link between socio-economic status and COVID-19 mortality risk varies from one country to the next, therefore local context seems to play an important role in the difference in outcomes.

Higher levels of deprivation have been associated with higher COVID-19 mortality in several jurisdictions. In England, a 1 percentage point increase in the proportion of the population experiencing income deprivation was found to lead to a 2% increase in COVID-19 mortality rates (Rose et al., 2020[22]). In Scotland as well, mortality rates were two times higher for those from the most deprived areas, controlling for age and sex (Lone et al., 2021[23]). A strong gradient of excess mortality and socio-economic status was also found in Chile (Mena et al., 2021[24]). Those in greater poverty and living in urban areas experienced larger decreases in life expectancy during 2020 (Mena and Aburto, 2022[25]).

Nevertheless, other studies have not shown a conclusive link between socio-economic status and COVID-19 mortality. In Germany, one study found no evidence of a link between poverty and COVID-19 mortality during the first wave of the pandemic (Ettensperger, 2021[26]). In Wisconsin, USA, poverty was found to be associated with higher rates of admission to the Intensive Care Unit, but not higher rates of death (Muñoz-Price et al., 2020[27]). Supporting these results, a study using US Census data did not show income or poverty to be a significant factor in predicting mortality (McLaren, 2020[28]).

The drivers of these disparities and the potential increased mortality risk for lower socio-economic groups varies across countries. A common explanation put forward is that lower socio-economic groups have a higher incidence of comorbidities that increase the mortality risk from COVID-19. In the United States, those with either lower education or lower incomes have higher rates of every medical risk factor (Wiemers et al., 2020[29]). In Chile, people living in lower socio-economic areas are more likely to be overweight and live in crowded conditions (Mena et al., 2021[24]). However, in England, the higher mortality risk for more deprived groups was not significantly explained by medical risk factors (Williamson et al., 2020[30]).

Access to medical care and health services is another potential driver of observed differences. In Chile, lower socio-economic neighbourhoods experienced more testing delays (Mena et al., 2021[24]).

Higher rates of infection may also play a role. Lower socio-economic groups may be more likely to have occupations that do not allow for teleworking, increasing their risk of infection. In Chile, lockdown measures were less effective at reducing people’s mobility in more disadvantaged areas (Mena et al., 2021[24]). Lower socio-economic groups in South Korea were also shown to be at higher risk of contracting COVID-19, particularly for those over the age of 60 (Oh, Choi and Song, 2021[31]).

Difference by ethnicity

Large disparities of mortality rates due to COVID-19 across ethnic groups have been observed in some jurisdictions. In the United States, Black, Hispanic, and Native populations have been at least twice as likely to die of COVID-19 compared to the White population (Center for Disaease Control and Prevention, 2021[32]). This led to a reduction in life expectancy in 2020 for Black people and Hispanic people that was two to three times greater than for white people (Woolf, Masters and Aron, 2021[33]). In England, the Black male population’s mortality risk was 3.7 times that of the White population during the first wave of the pandemic, and nearly all ethnic minorities were at higher risk of death than white people. During the second wave, the mortality risk for the Bangladeshi population increased substantially to 4-5 times that of the White population (Office for National Statistics, 2021[34]).

The higher risk to ethnic minorities is clear, though factors other than ethnicity are likely driving these results. One study in Louisiana confirmed that while Black people had a much higher rate of hospitalisation and deaths than white people, race itself was not an explanatory factor in the conditional survivor probability when controlling for other factors (Price-Haywood et al., 2020[35]).

There are several explanations put forward to explain observed differences across ethnic groups, including that they tend to be from more disadvantaged backgrounds, have higher rates of comorbidities, or have higher rates of infection. However, there is not strong evidence supporting the explanation that these populations tend to more often be from lower socio-economic backgrounds. One study in England showed that only a small part of the excess risk could be attributed to higher levels of deprivation (Williamson et al., 2020[30]). Another study in Wisconsin, USA, found no strong relationship between socio-economic status and race (Muñoz-Price et al., 2020[27]). An analysis using US Census data also found no evidence that income, poverty rates, or educational differences were driving the racial disparities for Black and Native populations, though education did seem to be a factor for differences observed for the Hispanic and Asian populations (McLaren, 2020[28]).

That minority populations suffer from higher rates of comorbidities seems to be a more plausible explanation for their increased mortality risk. In the United States, Black people have a higher prevalence of most of the COVID-19 risk factors than whites people (Wiemers et al., 2020[29]). In one study in Louisiana, USA, Black patients had a higher prevalence of obesity, diabetes, hypertension, and chronic kidney disease (Price-Haywood et al., 2020[35]). In contrast, another study in England showed that a higher prevalence of medical problems did not fully explain observed disparities (Williamson et al., 2020[30]).

Higher infection rates may be another explanatory factor for observed ethnic disparities. In the Wisconsin study, Black people were more likely to test positive for COVID-19, even when controlling for demographics, health and geography (Muñoz-Price et al., 2020[27]). Another study linked the increased risk to the use of public transportation and to the prevalence of heath support workers in the population (e.g. home aids, nursing assistants), in line with the theory of increased exposure leading to higher rates of infection (McLaren, 2020[28]).

Healthcare access

The COVID-19 pandemic caused significant disruptions to health services, including essential and emergency care that could have led to excess mortality from health problems other than COVID-19. A survey by the World Health Organization (WHO) found that 94% of the 135 responding countries experienced some disruption to essential health services, and over a third of the countries experienced disruptions to over half of their services. This included potentially lifesaving emergency, critical and operative interventions, which were disrupted in 20% of the countries. Over 40% of countries had disruptions to mental, neurological and substance abuse services, and a third experienced disruptions related to pre- and post-natal care. While less impacted, 26% of high-income countries still experienced disruptions (World Health Organization, 2021[36]).

Disruptions to health services, in particularly urgent care services, likely led to an increase in mortality for those unable to obtain needed treatment. One survey in the United States indicated that 1-2% of individuals surveyed were not able to access needed urgent care in the prior two months specifically because of the pandemic (Center for Disease Control and Prevention, 2021[37]). Deaths from Alzheimer’s and heart disease significantly increased in the United States during the peaks of the pandemic (Woolf et al., 2021[38]). The United Kingdom estimated that 6 000 of the excess non-COVID-19 deaths in March and April 2020 were due to changes in emergency care, compared to 42 000 deaths attributed directly to COVID-19. Another 10 000 are estimated to have died as a result of changes to adult social care, including early discharge, lack of emergency health care, and changes in the quality of care (Office for National Statistics, 2020[39]).

Avoidance of health care facilities because of a fear of being infected also likely played a significant role in the increased deaths among those not receiving needed care. In Northern Italy, emergency visits and hospitalisations decreased across all age groups and all types of diagnoses shortly after the first confirmed COVID-19 case in Italy. However, out-of-hospital mortality from neoplasms, cardiovascular and endocrine diseases significantly increased during lockdown, indicating that these individuals were not seeking needed care at the hospital (Santi et al., 2021[40]). Similarly, in Denmark, non-COVID-19 hospital admissions decreased by 30% after the first lockdown, and by 22% following the second lockdown after trends had returned to baseline levels. Despite this, mortality rates for non-COVID-19 diseases increased by over 20% during the lockdowns, and mortality rates from respiratory diseases, cancer, pneumonia, and sepsis remained higher over the entire period (Bodilsen et al., 2021[41]). In England and Wales, deaths from ischaemic heart disease, asthma, and diabetes increased, despite a reduction of these deaths in hospitals, indicating that many of these deaths were due to not receiving care (Kraindler, Barclay and Tallack, 2020[42]).

Disadvantaged groups of the population were in many cases more likely to experience reduced access to health care services. In Europe, a strong socio-economic gradient was observed by socio-economic status and previous health conditions for those experiencing foregone, postponed, or unavailable care, meaning that those who were more economically vulnerable and in poor health had less access to the health system (Börsch-Supan, 2021[43]). In the United States, the proportion of individuals not having access to urgent care because of the pandemic was negatively correlated with education level (Center for Disease Control and Prevention, 2021[37]). In addition, Black, Hispanic, and disabled populations were more likely to avoid urgent or emergency care during the first wave of the pandemic (Czeisler et al., 2020[44]). Hospital restrictions also seem to have been unbalanced in some cases, with sites caring more for Black populations being more impacted by lockdown measures. In a study on US patients with prostate cancer, prostatectomies decreased by over 90% for Black people compared to only 17% for white people, a difference not explained by the clinical parameters such as risk factors and age. While surgical treatments were restricted during lockdowns to prioritise those needing emergency care, some sites experienced increased surgical volume while those treating a higher proportion of Black patients paused surgeries completely (Vince, 2021[45]).

Capacity constraints and diminished resources potentially also put developing countries at increased mortality risk, especially children. Vaccination programmes against diseases other than COVID-19 in particular have been significantly disrupted. In April 2021, vaccination programmes in 50 countries were still postponed, meaning that 228 million people faced an additional risk of contracting life threatening diseases such as measles, polio, and yellow fever (WHO, 2021[46]). Missed vaccinations may also reduce herd immunity, presenting a larger risk to these populations as a whole. This is not without precedent. During the Ebola outbreak in 2014, vaccinations for infants under one year fell by 75%, vaccinations for measles fell by 20%, and around half of the children in the three most affected countries did not receive all of their routine vaccinations (Elston et al., 2017[47]).

Past experience has shown that the unavailability of health care or the reluctance to seek health care during health crises can be particularly detrimental to pregnant women and children, especially in developing countries. At the height of the Ebola outbreak in 2014 in Sierra Leone, maternal mortality increased by 170%, and still births increased by 40%. Over that year, reduced access to routine health services increased maternal and child mortality by 22% and 25%, respectively, with preventable and treatable infectious diseases being a major contributor to the latter (Elston et al., 2017[47]). Applying this experience to the COVID-19 pandemic, one theoretical model estimated that child mortality could increase by up to 45%, and maternal mortality by up to 39%, in low-income and middle-income countries. 60% of the increase in maternal deaths were due to reduced access to key childbirth interventions, while 40% of the increase in child deaths were due to reduced access to treatments for pneumonia, sepsis, and diarrhea (Roberton et al., 2020[48]).

Lockdown measures

The strict lockdown measures that many governments implemented during the peak waves of the COVID-19 pandemic had a significant toll on the mental health and well-being of the populations impacted. In the United Kingdom, the proportion of adults experiencing some form of depression in early 2021 doubled from pre-pandemic levels, with young adults and women more impacted (Office of National Statistics, 2021[49]). Similarly, the proportion of adults having symptoms of anxiety or depression increased by 5 percentage points over the period from August 2020 to February 2021, with young adults being particularly impacted (Vahratian et al., 2021[50]). Such declines in well-being can lead to potentially fatal detrimental behaviour linked to substance abuse or even suicide. Declines in well-being at home may also pose a threat to those in abusive relationships. On the positive side, in some jurisdictions social distancing may have reduced the number of homicides during lockdown periods, reduced traffic fatalities, and reduced fatalities from other contagious diseases such as seasonal influenza.