Age and Morbidity Trends related to COVID-19

I am conducting a county-level assessment of COVID-19 in relation to age demographics and comorbidities of the exposed population.  This blog post presents some preliminary results as part of the analysis phase of the project.  The causal relationship between coronavirus, age, and underlying conditions will be examined using geographically weighted regression (GWR). COVID-19 incidence rate and mortality rate function as the dependent variables. The independent or explanatory variables include percent population in different age cohorts and mortality or prevalence rates pertaining to underlying conditions, such as cancer, diabetes, and cardiovascular disease.  Before executing GWR, I created some thematic maps displaying COVID-19 incidence and death to case ratio normalized by age and comorbidity to examine some general trends in the data.  The maps refer to the second peak period of the virus that took place between 06/01/20 and 07/31/20.

The featured map shows COVID-19 incidence rate by population in the 75+ age cohort.  The highest incidence rate for this category was 3,315 cases per 100,000 of the population.  This was significantly higher than the incidence rate for the 20 -34 age cohort, which was 452 cases per 100,000 of the population.

The second map (displayed below) shows COVID-19 death to case ratio by population in the 75+ age cohort.  The highest mortality rate for this age group was 7.2 per 100 of the population compared to 4.9 per 100 of the population that was recorded for the 20 – 34 age group.

The third map shows COVID-19 incidence rate by population with diabetes.  The highest incidence rate by percent population with diabetes was 771 cases per 100,000 of the population.

It is premature to assume that the spatial trends displayed on the maps indicate causal relationships between COVID-19, age, and comorbidity.  However, they do reveal some interesting correlations between COVID-19 incidence and mortality in the elderly population and among those with underlying conditions.



Naomi Lazarus

Dr. Naomi W. Lazarus is an Assistant Professor of Geosciences in the Department of Geography and Planning at California State University, Chico. She earned her B.A. and M.A. in Geography at Binghamton University, New York and has a PhD in Geography from the University of Connecticut, Storrs. Dr. Lazarus’ research examines the demographic, social, and economic impacts of natural and anthropogenic hazards. Her current research examines spatial and temporal trends in the dengue virus in South Asia. Dr. Lazarus teaches courses in GIS, cartography, and quantitative methods at CSU Chico.


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