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Study: Why is the Covid mortality rate so different between countries?

The Covid mortality rate is more associated with social factors such as life expectancy, the public health context, the economy and financial support, and the environment (temperature and UV), than with the rigour of measures to combat the pandemic, according to a study that analyses the heterogeneous spread of Covid in the different continents and identifies the non-viral parameters most associated with the mortality rate.

The paper contradicts the perception that more “developed” countries would have more resources available to minimize the impact of Covid-19 on mortality. According to the paper, while countries with “optimal human development niche with favourable health, demographic, environmental and economic parameters” are undeniably positive for people, they now “expose populations to higher infectious (Covid-19) and physical (heat waves) vulnerabilities“.

According to the report, Covid-19 has generated a wide range of responses from governments around the world, but the contagion and mortality curves are very similar across countries.

“This is reinforced by our conclusions regarding the lack of any association between these curves and the actions of governments during the pandemic. In this sense, demographic, health, development and environmental determinants seem far more important to anticipate the lethal consequences of Covid-19 than government actions, especially when such actions are more driven by political than health objectives”.

The parameters studied divide the countries into two groups.

Economy and life expectancy

Countries with higher Covid-19 mortality rates have high GDP, high income and good economic support policies. Their societies are more developed, older, with high (but slowly increasing) life expectancy. Associated countries with low Covid-19 mortality rates have lower GDP, low life expectancy (with high margin of progression).

“During a pandemic, the main indicator of countries’ health fragility can be seen in the proportion of older people (who were the main target of SARS-CoV-2). This indicator is most common in countries with longer life expectancy, which is why they have higher mortality rates when new aggressors emerge”.

Previous studies have illustrated the relationship between fragility and mortality. For example, the 2003 heat wave killed between 30,000 and 50,000 people in Europe – 15,000 in France alone, affecting 80% of older people. Covid-19 mortality was the highest among older people in the world. The move towards longer life expectancy will therefore expose higher proportions of people to high mortality rates, especially when facing mass threats or when environmental conditions are more extreme.


The development provided by a high GDP associated with longer life expectancy favours a less active life style“. The study says that countries with higher mortality rates have more chronic diseases (e.g. cardiovascular diseases and cancer) associated with important metabolic risk factors (inactive lifestyle, sedentariness, obesity, etc.). These health problems increase the risk of hypertension, diabetes and cardiovascular problems, the most frequent comorbidities associated with Covid-19 mortality.

“With a more prevalent epidemiological transition to chronic diseases, countries with high life expectancy have also increased the concomitant risks, restricting their margins of adaptability”.

The paper stresses that in the case of Covid-19, the promotion of physical activity can help “to increase immunity and resilience of populations and prevent sedentary behaviour“.

“Political strategies that restrict physical activity (e.g. the closure of sports facilities) can curb the strengthening of the immunity of the population in response to present and future viral aggressors”.


High temperature and UV levels are associated with low mortality rates, i.e. in northern and western countries the impact of Covid-19 is greater.

The Portuguese Sea and Atmosphere Institute (IPMA) has published a scientific paper – “Potential of Solar UV Radiation for Inactivation of Coronaviridae Family Estimated from Satellite” – which assesses the potential of solar UV radiation for the inactivation of SARS-CoV-2 in ambient air. The results show that solar UV radiation has a high potential for inactivating these viruses, depending heavily on geographical location and season.

In tropical and subtropical regions (e.g. São Paulo, 23.5°S), the daily survival fraction of the virus is less than 0.01 % all year round, while at higher latitudes (e.g. Reykjavik, 64°N) this fraction can only be found in June and July.

“For example, in Lisbon and in March, it would take 3 to 10 hours for the virus to be eliminated by UV radiation; on the other hand, in winter we have times for sterilization of more than 20 hours, i.e. one day is not enough to sterilize surfaces outside”.

IPMA underlines that these data have important potential practical implications in terms of Public Health recommendations.

This year of 2020 UV Index levels were very high throughout May, when the number of Covid 19 cases was sharply reduced and lethality was reduced, with these levels remaining low until mid-September, when UV levels were significantly reduced,” indicates IPMA, citing other variables.


The geographical relationship between the Covid-19 mortality rate and latitude shows that latitude ranges [25-65°] represent 78% of all recorded Covid-19 deaths. In mainland Europe, this area includes Spain and Italy up to the southern part of Sweden. In the Americas, it covers the state of Texas down to Hudson Bay; southern Brazil and the states below this area. In Africa: the Maghreb states and South Africa). This area includes the states with the highest mortality rates recorded.

Negative (US) longitudes were also associated with higher mortality rates. The [-35/-125°] longitude range (West) delimited an area where 57% of all Covid-19 deaths were recorded.

The third axis shows a relationship between mortality and longitude, obesity and sedentariness. American countries have a higher obesity rate and a higher Covid-19 mortality rate; Asian countries have lower obesity rates and lower Covid-19 mortality rates.

Background to the study

The report examined the potential link between these five areas – demography, public health, the economy, politics and the environment – and Covid-19 mortality during the first 8 months of 2020. The study analysed data from 160 countries, representing a total of 846,395 Covid-19 deaths by 31 August 2020, but noted that the methods of counting and recording ‘Covid death’ vary between countries and that the ‘waves and peaks’ of the pandemic are equally distinct.

Although they present extremely important data and a significant territorial coverage, some caution is important when analysing these results.

For example, an observational study does not make it possible to establish causal relationships, only correlation.

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