On Monday, the Chinese Centre for Disease Control and Prevention (CCDC) published the results of a study on COVID-19 outbreak analyzing all cases diagnosed as of February 11, 2020 in Mainland China. The total of 72,314 patient records analyzed included 44,672 confirmed cases, 16,186 suspected cases and 10,567 clinically diagnosed cases.
The demographic characteristics of the confirmed cases and the associated outcomes clearly shows the differential effect of the disease on various age groups. While 46.5% of confirmed cases represent patients younger than 40, only 6.3% of total deaths have been reported within that age group and only a single death below 20 was among those. On the other hand, those who are older than 60 represent only 31.1% of confirmed cases but 81.0% of total deaths. Why COVID-19 is hitting the elderly hard?
Until February 11, only the confirmed cases were associated with COVID-19 in official statistics but suddenly China started to count the clinically diagnosed cases too. With this change, the number of cases jumped up by nearly a third. A disease is what we define and so is the cause of death. When a definition changes, many healthy individuals become sick and vice versa. In November 2017, the US clinical guidelines on the threshold defining high blood pressure was lowered from 140/90 mm Hg to 130/80 mm Hg. Consequently, the percentage of US adults with hypertension increased immediately from 32% to 46%.
Economists explain life and death using the health capital model. In the widely used model introduced by Michael Grossman in 1972, individuals inherit an initial stock of heath that depreciates with age. They can invest in inputs such as medical care, diet, exercise and living environment to increase this stock while various diseases act as random shocks to decrease the stock of health capital. Death occurs when the stock falls below a certain minimum level.
Based on the Grossman model a disease can cause death when the initial endowments are very low, when most of the health stock has gradually depreciated or when the magnitude of an adverse health shock is very large. The COVID-19 does not appear to cause a huge health shock itself. Many people have mild symptoms and most of them recover easily. The fatality rate is very low among the young, so it can’t be due to low initial endowments. Most likely, COVID-19 can be the last fatal punch on those who have a limited residual stock of health capital.
COVID-19 does not kill itself. The immune response to the virus destroys lung tissue and cause inflammation ultimately cutting off the oxygen supply to the body causing death. Lung health of a person can deteriorate due to various other causes- smoking and air pollution are examples. Yet, when a person has been tested positive for COVID-19, we solely attribute that death to the virus.
In many media reports during the past month, we saw Chinese people with their faces covered with masks to protect themselves from COVID-19. Facemasks, however, are not new to most Chinese cities. At least for two decades, people living in smog-filled large Chinese cities have been routinely wearing facemasks to minimize the health risks of air pollution.
The great economic prosperity and urban growth in China during the recent past have also resulted in the deterioration of the quality of air in most parts of China, Beijing-Tianjin-Hebei and surrounding areas in particular. An assessment by the United Nations Environmental Programme (UNEP) just before the 2008 Summer Olympics in Beijing noted that addressing Beijing’s poor air quality was a top priority in planning for the Games. By that time health concerns among athletes and officials over air quality in Beijing had attracted wide international media coverage. Due to various regulatory measures implemented prior to the Olympic games by Chinese authorities, Beijing smog cleared after many years in 2008. These “Olympic Blues”, however, didn’t last long since most of the regulatory measures implemented were temporary.
China has been fighting air pollution aggressively since 2013 and a recent report by UNEP shows that annual average concentration of PM10 in Beijing has decreased by 55.3% during 1998-2017. Yet, Beijing’s ambient air still exceeds China’s air quality standards and the World Health Organization’s recommended “safe” levels. China still is one of the countries with most polluted air.
According to a study published in 2016 which analyzed the effects of temporary improvement in air quality in Beijing in 2008 on mortality, 285,000 premature deaths in urban China could be averted annually if PM10 concentrations were to decrease by 10 percent. Another study published in 2017 shows that that the air quality related deaths in China from stroke, ischemic heart disease and lung cancer increased from approximately 800,000 cases in 2004 to over 1.2 million cases in 2012.
As data show air quality in Wuhan and the surrounding area has been as poor as in Beijing during the past decades. If we go back to Grossman’s health capital model, this should have affected the health stock of most people living in this part of the country, particularly the elderly. When you just have a small health stock left, you don’t need a large shock to exhaust it. Is that what happened with COVID-19? If so, can we call COVID-19 the sole culprit? Is bad air quality in China a partner in crime?