Last week, I was asked if it would be OK if 20 family members visited one of my patients who is in his 80’s over the holiday weekend. My reflexive response was “Don’t come!” but it raised the question of what is the probability of dying should this patient get infected by COVID-19 and how does age effect mortality rates? Although we all know that age is a risk factor for death from COVID-19 infection, it turns out that specific probability statistics are hard to come by.
The U.S. Centers for Disease Control regularly posts information about the COVID-19 hospitalization rate by age and we know that older persons are more likely to be hospitalized than younger persons. For example, the hospitalization rate for people age 18-29 years old is 34.7 per 100,000 whereas the hospitalization rate for people over the age of 85 is 573.1 per 100,000. That means that an elderly person at 85 years old is sixteen times more likely to be hospitalized with COVID-19 than a young adult who is 25 years old. But this data does not tell us about the probability of death for different age groups.
The Ohio Department of Health regularly posts information about the number of Ohioans who have died from COVID-19 by age. This graph shows the COVID-19 deaths in Ohio as of July 1, 2020. It is striking that 1,516 deaths (53% of the total) occurred in people over the age of 80 whereas only 2 deaths have occurred Ohioans under the age of 20. However, the Ohio ODH does not post the total number of cases by age and so we still cannot determine the probability of death for different age groups. For that information, we have to turn to California.
The California Department of Public Health regularly posts both the number of infections AND the number of deaths for different age groups. This is the data from California as of July 1, 2020. By dividing the number of deaths by the number of cases for each age group, we can calculate the probability of death if a person in that age group becomes infected with COVID-19. The numbers are astounding: 25% or one out of every four people over age 80 who get infected with COVID-19 will die of the infection. On the other hand, a young adult between age 18-34 years old who gets infected with COVID-19 has a 0.084% chance of dying (or 1 death for every 1,196 infected persons). That means that an 85 year old person is 300 times more likely to die if infected with COVID-19 than a 25 year old infected with COVID-19. One a more personal front, if one of my children and I both get infected with COVID-19, I am statistically 38 times more likely to die than my child.
So, why is age such a striking risk for death by COVID-19? Although it is true that older people are more likely to have debilitating diseases such as heart failure and COPD that could make death more likely, I do not believe that this fully explains the association of age with COIVD-19 mortality. Furthermore, children almost never die of COVID-19; in Ohio, there have only been 2 deaths in those under age 20 and in California, there have been no deaths in those under age 18. One possible explanation that has been proposed is age-related changes in the level of the cell membrane receptor ACE2, a protein that the COVID-19 virus binds to in order to get inside of cells.
Virology research will eventually give us an answer to the question of why COVID-19 preferentially kills older people. But for now, I’ll stick to my original answer to my 83-year old patient’s family members question about having a family reunion at his house over the holiday weekend… don’t do it.
July 3, 2020