There are now enough cases of COVID-19 infection here in Louisiana that the state DOH has included a new daily chart, providing the number of cases by relevant age groups. Good on them for their continued efforts at public information and Transparency.
However, the actual case numbers per group are easily misleading because they are not adjusted for the proportion of our citizens who make up each age group. If the number of cases in two different groups is nearly the same, but one group has twice as many people in that age range, the relative risk for each group is much different.
Here is the state data reinterpreted to include the 2020 distribution of our population in the various age groups from World Population Review.
Finally a graph that shows relative risk for each group as of today March 23, 2020.
A relative risk (RR) of 1.0 implies the observed number of cases within a particular group is what would be expected based on their proportion of the population. A RR higher than 1.0 implies a group is showing a higher risk than expected, than if the infection were equally prevalent across the entire population.
It is becoming clearer each day that the COVID-19 infection risk occurs primarily in adults over the age of 18. So far, we have seen only 4 cases in children, though they comprise almost 25% of our state’s population.
For the graphs and analysis the risks are given for the adult only population (based on 1,168 cases diagnosed to date).
The age trends can be followed every day going forward. For now, the primary observation is that in general the risk appears to increase fairly steadily with age, and the largest RR is for those age 70 and above (1.77) with about twice the average expected risk.
There is one unexpected bump though. The observed relative risk for those ages 40-49 is a fair bit higher than expected (about 25%). So far, their risk is as high as that for seniors between ages 60-69. If this turns out to be a persistent finding, no immediate explanation for he extra elevated risk is known yet.
Keep an eye out.
Thanks Louisiana Public Health officials for doing your part to keep us informed, without trying to bend the publicity curve.
