A new study of 5700 consecutive COVID-19 patients hospitalized in the New York area is making waves because it reports a high rate of underlying chronic disease, seemingly amplifying findings from Wuhan and elsewhere. But what is striking about this group of severely ill COVID-19 patients is not so much their associated chronic conditions as how similar they are to much of the general population.
The study, published in JAMA, reported obesity in 47.7 percent of patients, very much like the rate among adults generally: 44.8 percent of 40-59-year-olds and 42.8 percent of those over age 60 are obese. For high blood pressure and diabetes, the rates of disease in the COVID-19 patients closely resembled the rates in the older population in general. The study found high blood pressure in 56.6 percent of the COVID-19 patients; that’s awfully close to the rate of 60 percent found in the general population among people over age 65—and considerably higher than the rate of 33.2 percent found in the general population among people aged 40-59. And the study noted that diabetes was present in 33.8 percent of the very ill COVID-19 patients; that is fairly similar to the rate of 27 percent found among the elderly in general—and markedly higher than the 17.5 percent typically found in the general population of 45-64-year-olds.
To better understand the significance of the observations about chronic conditions in the COVID-19 patients, the authors of the JAMA article need to examine age-specific rates of those disorders. Without this information, we can’t say very much about risk factors—except that obesity doesn’t seem to be much of a risk factor at all since its rate in the hospitalized COVID-19 is very similar to that in the general adult population. What about hypertension and diabetes?
Since the median age of the patients in the JAMA study is 63, that means that about half the patients are elderly and about half are not. If all we know is that the rate of high blood pressure in the patients is 57 percent, then there are three possibilities: 1) that 57 percent figure applies across the board, regardless of age; 2) the rate among the half of the study population that’s over 65 is greater than 57 percent (in which case the rate among the half that are under 65 is less than 57 percent); or 3) the rate among the half of the study population that’s over 65 is less than 57 percent (in which case the rate among the younger patients is more than 57 percent).
Let’s put sample numbers on these 3 situations, comparing them to what we know about rates in younger and older people in general. In the first case, where the 57 percent applies to everyone, regardless of age, this would mean that the risk of high blood pressure in the older population is the same (or a little lower) than in older people without COVID-19, where it’s 60 percent; and much, much higher than in the younger population, where it’s 33 percent. In the second case, let’s suppose the actual rate of hypertension in the older COVID-19 patients is more like 70 percent (higher than the 60 percent in the well elderly); that would imply the actual rate in the younger COVID-19 patients must be around 44 percent (higher than the comparable rate in healthy younger patients of 33 percent). In the third case, let’s suppose that an average hypertension rate of 57 percent means the actual rate of hypertension in the older COVID-19 patients is 44 percent (much lower than among healthy elderly) and the actual rate among younger COVID-19 patients is 70 percent (much, much higher than among healthy younger adults). What’s noteworthy among these three possibilities is that only in one of them is hypertension a risk factor in the elderly (case 2); in the other scenarios it's either not a risk factor or is actually protective. Moreover, if it is a risk factor, it may well confer only modestly increased risk.
Whatever the relationship between chronic disease and the severity of COVID-19, what is clear is that Americans as a whole have high rates of chronic disease. A recent international comparison of health found that the US has a rate of chronic disease and obesity that is twice that of other developed countries. Among fee-for-service Medicare beneficiaries, the latest statistics reveal that 20 percent have between 2 and 3 chronic conditions; another 23 percent have 4-5 chronic conditions, and fully 17 percent have 6 or more chronic diseases.
Before we make older people with diabetes or high blood pressure unnecessarily anxious about contracting COVID-19—or falsely reassure those older people who don’t have diabetes or high blood pressure that they are at low risk—we need a more careful analysis. Perhaps the real take-away message from the JAMA study is that the U.S. needs to do a better job preventing chronic disease.