Studies show that more than half of coronavirus disease 2019 (COVID-19)-related deaths in Mexico are in middle-aged adults (45 to 65 years old), which is in stark contrast to the deaths in developed countries. Mexico, with its young population, has a high prevalence of metabolic diseases such as diabetes and obesity that contribute to adverse COVID-19 outcomes. COVID-19 infection in populations with a combination of undetermined comorbidities could be particularly risky.
Determining age-stratified COVID-19 case fatality rates and relative risk of various comorbidities
In a recent medRxiv* preprint paper, researchers from Mexico demonstrated how they calculated age-stratified COVID-19 case fatality rates, years of life lost (YLL), and relative risk for 9 comorbidities and 23 comorbidity combinations in a retrospective study. The study cohort comprised 905,579 individuals with COVID-19 confirmed by real-time polymerase chain reaction reverse transcription (RT-PCR) tests and 89,167 deaths, until 2 Nov 2020.
We analyzed COVID-19 datasets updated by Mexican health authorities, available at , that include all symptomatic patients evaluated as probable COVID-19, since outbreak start, along with their comorbidities and outcomes (retrospective cohort).”
Chronic kidney disease had highest relative risk for mortality and relative risk decreased with age
The results of the study showed that chronic kidney disease had the highest relative risk for fatal
COVID-19. Kidney disease was followed by diabetes and immunosuppression, which had higher relative risk than obesity or hypertension as the only comorbidity. The combination of diabetes and hypertension with or without obesity had a relative risk as high as chronic kidney disease as the only comorbidity (more than 3 in under 60-year-olds). Interestingly, the relative risk of comorbidities decreased with age, with values nearing 1 after age 60.
Comorbidities increase COVID-19 fatality risk in young and middle-aged adults
The findings suggest that in Mexico, comorbidities increase COVID-19 fatality rates mostly in young and middle-aged adults. The analysis indicates that advanced metabolic disease contributes more to COVID-19 fatalities in younger adults in Mexico – especially in the case of multiple morbidities or diabetes in individuals below 60.
Given that a large proportion of Mexican adults are obese (36%) or overweight (39%), environmental and genetic factors that favor metabolic disease could be contributing to early-aging in Mexicans, first driving metabolic-inflammation then leading to-, or merging with-, age-related inflammation.”
About 38% of YLL to COVID-19 disease was attributable to the interaction between COVID-19 and the pre-existing comorbidities, mainly various combinations of diabetes, obesity, and hypertension. Yet, about one quater of COVID-19 related deaths and one-third of YLL have occurred in individuals without any known comorbidity.
Despite its young population, Mexico is among the ten top countries in COVID-19 mortality, with ~7.5% of world deaths.”
Mexicans aged 45 to 64 years are at higher risk of COVID-19 mortality, with or without comorbidities
The COVID-19 outbreak patterns in Mexico suggest that middle-aged adults of age between 45 and 64 years are at higher risk of COVID-19 mortality, more so if they have pre-existing chronic metabolic diseases. However, individuals in this age group were found to be at higher mortality risk even in the absence of comorbidities, making them a key group of concern after the elderly population.
A shift towards middle-age distribution of COVID-19 fatalities is likely not unique to Mexico and awaits systematic exploration in other low and middle-income populations.”
According to the authors, COVID-19-related mortality in middle-aged adults could be because of the gradual decline in health that comes with aging. Unfortunately, this health decline presents earlier in economically backward populations that also have more chances of exposure to SARS-CoV-2 and less access to personalized medical attention.
The authors believe their analysis offers key information that helps distinguish vulnerable subpopulations and could help direct special attention to them during COVID-19 outbreaks. It also highlights key areas, they note, for prioritization during SARS-CoV-2 immunization drives. The findings of this study agree with emerging data on the risks of comorbidity for COVID-19 patients. Additionally, the study also offers new data on the age-stratified relative risk of 23 comorbidity combinations that can also be extrapolated and applied to other populations with comparable demographics.
Our analysis provides information to distinguish vulnerable subpopulations for special attention during outbreaks and for SARS-CoV-2 immunization, when available; and is compatible with the emerging knowledge about risks of comorbidity for COVID-19.”
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.