Adjusted age-specific case fatality ratio during the COVID-19 epidemic in Hubei, China, January and February 2020

Julien Riou; Anthony Hauser; Michel J Counotte; Christian L Althaus

Estimates of age-specific SARS-CoV-2-associated mortality in symptomatic patients are particularly important for clinicians, who need to assess prognosis and prioritize care when healthcare systems are overwhelmed as the case now appears in northern Italy. The age-specific differences in mortality can be intuitively understood by comparing the age distributions of cases and deaths in both settings ( Figure 1B and D) , with an even more marked age shift in Italy resulting in higher mortality estimates in that group ( Figure 3A and 5A). The specific causes of this age trend are unknown, but early discussions have focused on the associations between SARS-CoV-2 and comorbidities such as diabetes and hypertension and the role of ACE inhibitors [35] . Here, we simply compared the prevalence of four comorbidities (diabetes, chronic respiratory disease, cardio-vascular disease and hypertension) among deaths associated with SARS-CoV-2 infection in China with the expected prevalence according to the age distribution of deaths. Only for diabetes was there an excess among SARS-CoV-2-associated deaths. The prevalence of the other comorbidities was similar or lower than expected in a Chinese population with that age distribution. The reliance on data that are not gender-disaggregated means that hypotheses about the potential influence of gender-related differences like smoking patterns could not be explored. This ecological observation does not refute any causality between these comorbidities and SARS-CoV-2-related mortality, as the age trend itself may be related to a higher prevalence of ageing-associated diseases, but highlights that the very specific age pattern of mortality associated with SARS-CoV-2 infection must be accounted for when discussing association with comorbidities.