This post is an update to the series of posts made about one month ago analyzing the distribution of cases, hospitalizations, and deaths by age cohort. As I noted then, the state has made it quite difficult to perform this analysis for two primary reasons:
(1) Age-related information is only published weekly, but on a rolling two-week basis (the state stopped providing daily information on August 11). Because the age-related information covers two weeks, weekly figures must be estimated.
(2) The published totals in the weekly reports do not align with those for the corresponding period in the daily reports.
To circumvent these issues, I developed a methodology outlined in a prior post (https://www.masscoronavirus.net/massachusetts-covid-breakdown-by-age-part-i-methodology/) to estimate the age distributions through time. I’m using the same methodology to extend the analysis through November 7th for cases and deaths.
I had been relying on hospitalization data published as part of the race / ethnicity daily reports to calibrate the weekly age-based hospitalization data – which tended to severely under count hospitalizations compared to the daily reports. However, the race / ethnicity report was dropped on November 2nd. I am working on an approach to estimate age-related hospitalizations, but won’t include it in this post.
As most everyone is aware, cases have increased dramatically since the beginning of October – almost tripling in the five weeks between October 3 and November 7. Obviously, case incidence rates are significantly higher than previously, as Figure 1 indicates.
As has been true since the end of July, case incidence rates have been higher for those under 60 compared to those over 60 – ranging from about 50% higher to more than double each week since the beginning of August. This case incidence rate differential appears to be generally holding, even as cases skyrocket.
This is evident from Figure 2, which shows the percentage of cases by age cohort over time. These percentages have held roughly steady since the end of July – with about 85% of cases in people under 60, and 15% of cases in people 60 and over. (This may seem very high for those under 60, but keep in mind that they represent 77% of the population in the state). In the past several weeks, there might be a slight trend to higher relative rates among those 60 and older, but it is difficult to determine whether this is just a normal fluctuation in the data or the start of a trend.
Unlike cases, which have increased significantly since October 3, deaths have increased modestly – up 37% to November 7th. This is positive news, but since deaths lag case diagnosis by at least several weeks, there is no guarantee this trend will continue. We can certainly hope that improved treatment protocols and the younger age of patients will keep deaths somewhat in check.
Figure 3 shows the death incidence rate by age cohort through November 7. Even though the death totals haven’t climbed as much as cases since October 3, the bulk of the increase is born by those 60 and older, as Figure 3 makes apparent. This is because over 90% of deaths are in the 60 and older population, and this percentage has been roughly the same for months.
Figure 4, which shows the percentage of deaths by age cohort, makes this clear. Although it is a bit difficult to see in the Figure, over the past five weeks the percentage of deaths in those 60 and older rose slightly – to 93% from about 91% in the five weeks prior.