Facemasks, Testing, Lockdowns and the Association with Country Wide COVID Mortality

An interesting preprint updated August 2020 by Leffler and others looked at determining the sources of variation between countries in per capita mortality from COVID-19. 

They looked at potential predictors of per capita Coronavirus related mortality in 200 countries by May 2020 and examined age, sex, obesity prevalence, temperature, urbanisation, smoking, duration of infection, lockdowns, viral testing, contact tracing policies and public mask wearing norms and policies.  They performed multivariable linear regression analysis.

They studied Coronavirus mortality in 200 countries, of which 183 had testing data, 169 had government policies scored by Oxford University and 152 fell into both.

The hundred lower mortality countries had 0.99 deaths per million population, in contrast with an average of 93.3 deaths per million population in the hundred higher mortality countries.  The median value was four deaths per million population.

They assumed that island nations might find it less challenging to isolate and protect their population.  However, 19 of 100 low mortality countries were isolated on islands compared with 28 of 100 high mortality countries.  It appeared that country surface area and population were not associated with coronavirus mortality.  So what did they find?

Population Characteristics

Countries with older populations suffered higher coronavirus mortality.  Countries with low mortality had on average 8.8% of the population over the age of 40 as compared with 18.2% in the high mortality countries.

The proportion of the population which was male was not associated with country wide mortality.

Smoking prevalence was on average 13.7% in low mortality countries and 18.4% in high mortality countries.

Obesity prevalence was on average 14.6% in low mortality countries and 24% in high mortality countries.


Colder countries were associated with higher Coronavirus mortality.  The mean temperature was 22.2oC in the low mortality countries and 14.1oC in the high mortality countries.


Urbanisation was associated with Coronavirus mortality.  On average 52% of the population was urban in low mortality countries whereas in high mortality countries the figure was 70%. 

Richer countries suffered a higher Coronavirus related mortality.  The mean GDP per capita was $9,060 in the low mortality countries and was $27,140 in the high mortality countries.  This is a staggering statistic.


As we all know, the World Health Organisation, the WHO initially advised against widespread mask wearing by the public as did the United States CDC.  The WHO reversed this decision and recommended facemasks to the public on June 5, 2020.

Despite these initial recommendations, a number of countries did favour mask wearing by the public early in the outbreak and as such, these countries experienced low coronavirus related mortality. 

In Mongolia and Laos, both of which had reported no Coronavirus related mortality by May 9, the public began wearing masks before any cases were confirmed in those countries. 

The authors identified 22 additional countries with recommendations or cultural norms favouring mask wearing within 20 days of the estimated onset of a country’s outbreak.  These countries included Japan, the Philippines, Macau, Hong Kong, Sierra Leone, Cambodia, Timor-Leste, Vietnam, Malaysia, Bhutan, Venezuela, Taiwan, Slovakia, St Kitts and Nevis, South Korea, Indonesia, Brunei, Grenada, Mozambique, Uzbekistan, Thailand and Malawi.  

The average mortality for these 24 early mask wearing countries was 1.5 per million by May 9 – 20 of the 24 were lower mortality countries.  

An additional 17 countries recommended that the public wear masks within 30 days of the estimated onset of their outbreak.  These included São Tomé and Príncipe, Czechia, Dominica, Bangladesh, Zambia, Chad, Benin, Sudan, El Salvador, Antigua and Barbuda, Myanmar, Bosnia and Herzegovina, Cote d’Ivoire, South Sudan, Kenya, Santa Lucia and Barbados.  

The average mortality by May 9 for this group was 8.5 per million.  In the countries not using masks by April 16 or not using them until 60 days after the start of the outbreak, the per capita mortality by May 9 rises dramatically if the infection had persisted in the country for over 60 days.  

On the other hand, countries in which masks were used from 16 to 30 days after infection onset had per capita mortality several orders of magnitude less by May 9.  When countries recommended masks within 15 days of the onset of outbreak, the mortality was so low.

For instance, for the early mask wearing countries in which the infection had arrived by January such as Thailand, Japan, South Korea, Taiwan, Macau, Hong Kong, Vietnam, Cambodia, Malaysia, the Philippines, the virus was present in the country by 80 or more days by April 16.  If masks had no effect, it would have been expected that these countries would have had a mortality well over 200 deaths per million.  Instead the mortality within these 10 regions was 2.1 million, approximately 100 fold reduction.

What about International Travel Restrictions?

The study found that the association of mortality with the timing of international travel restrictions was of borderline statistical significance.  In countries not recommending masks, the per capita mortality tended to increase each week by a factor of 62.1%.  In contrast, in countries recommending masks, the per capita mortality tended to increase by just 15.8%.

With international travel restrictions in place without masks, the per capita mortality increased each week by 14.1%.  Under lockdown without masks, the per capita mortality increased by 58.5%.

A country with 10% more of its population living in an urban environment than another country tended to suffer a mortality 14.5% higher.  A country in which the percentage of the population age 60 or over is 10% higher than another country tended to suffer mortality 206% higher.  A country with a prevalence of obesity 10% higher tended to suffer mortality 39% higher.


The study’s results confirm in the first four months of 2020 there was a marked variation between countries in relation to mortality from COVID-19.  Countries in the lower half of mortality experienced on average 0.99 deaths per million population COVID-19 related per capita mortality. 

This contrasted with 93.3 deaths per million in the remaining countries.  It was found to be statistically significant as independent predictors of per capita mortality in relation to urbanisation, population over 60 years of age, obesity, duration of the outbreak in the country, international travel restrictions and the period of the outbreak subject to cultural norms or government policies favouring mask wearing by the public.  

The study’s results support the universal wearing of masks by the public to suppress the spread of Coronavirus.  Certainly, it is highly unlikely that masks are harmful.

Some countries which use masks were better able to maintain or resume normal business and educational activities – for instance in Taiwan schools reopened on February 21, 2020 with parents directed to purchase four to five masks per week for each child. 

Limits on international travel were significantly associated with lower per capita mortality from Coronavirus.  On the other hand, nationwide policies to ban large gatherings and to close schools or businesses, tended to be associated with a lower mortality though not in a statistically significant fashion.  

Colder average monthly temperatures were associated with the high level of COVID-19 mortality.  However, the reason for this might be that when it is cold outside, one stays more inside and thus there is more spread of virus and its transmission.

There was no statistical support for the benefit of mass testing demonstrated but presumably one would consider a higher level of testing might identify essentially all coronavirus related deaths and still higher levels of testing combined with contact tracing might lower mortality.

In summary, older age of the population, urbanisation, obesity and longer duration of the outbreak in a country were independently associated with a higher countrywide per capita Coronavirus mortality.

International travel restrictions were associated with a lower per capita mortality.

However, other containment measures such as testing and tracing and the amount of viral testing were not statistically significant predictors of country wide Coronavirus mortality after controlling for other variables.

In contrast though, mask wearing by the public was independently associated with lower per capita mortality from COVID-19. 

The London General Practice encourages mask wearing at all times alongside social distancing and other barriers to the transmission of infection.

Translate »
Share This