ROCHESTER, Minn. -- A new study has learned that severe outcomes with COVID-19 are associated with lesser-noted biomarkers low HDL cholesterol and high triglycerides, and to an extent equal or greater than widely-emphasized underlying conditions like advanced age, diabetes and high BMI, or body mass index.
In shedding light on the metabolic backdrop for severe COVID-19 outcomes, the finding holds implications for dietary and medication practices and expands the list of health markers of high interest in predicting who faces a higher risk of severe outcomes from the illness.
The observational cross-sectional study, which means it can only show associations and not cause-and-effect, was published last week in the journal Nature Scientific Reports. It drew on a retrospective review of cholesterol values and COVID-19 outcomes for 1,411 hospitalized patients in Spain.
Researchers looked at the lipid profile of 1,305 patients before hospitalization and 106 patients during hospitalization with COVID-19. Over 190 of those patients had blood drawn both before and during hospitalization, allowing the researchers to rule out the effects of illness on metabolic biomarkers like cholesterol.
Illness is known to reduce blood cholesterol values through a number of mechanisms.
When it came to those blood lipids associated with severity of COVID-19 in hospital -- as measured by a need for mechanical ventilation, supplemental oxygen or vital organ assistance -- the authors found that lower HDL and higher triglycerides were associated with severe outcomes.
As a rule, HDL cholesterol and triglycerides tend to have an inverse relationship with each other. When one goes up, the other goes down.
In contrast, the authors reported, LDL cholesterol values, according to the study, "were similar between those with mild and severe COVID-19."
Millions of Americans take statins to lower their LDL, but the authors found "no important differences in baseline therapies, including statin therapy," between those who did better or worse with COVID-19, suggesting that medicating down LDL may have benefits but none in regards to COVID-19 severity.
A striking finding was the degree to which the LDL-triglyceride relationship "showed the same importance level as age and body mass index" and surpassed the significance of underlying conditions commonly of interest to health officials concerning the virus.
Specifically, the study found that a low HDL and high triglyceride lipid profile was associated with COVID-19 severity, whereas "in our patients, the body mass index and the prevalence rates of diabetes and obesity were similar between groups with a mild or severe COVID-19 evolution."
"A high triglyceride level associated with a low HDL-C concentration," the authors concluded, "must be considered as a marker of a poor prognosis."
For years, the numbers scrutinized most after getting back your bloodwork came down to two values, total cholesterol, and LDL or so-called "bad cholesterol." You wanted to keep them both below the official cutoffs for worry, which, in the case of total cholesterol was 200, and with LDL was 130.
Though millions of Americans continue to take statins daily to reduce their LDL, and a lesser proportion of the health-conscious public may make themselves egg white omelettes in the hopes of lowering their total cholesterol through sources of cholesterol in the diet, when it comes to cardiovascular health, both of those biomarkers have lost their powers of prognostication in recent years.
Decades-old research has percolated to the fore that LDL comes in different sizes, with the smallest size being that which is worrisome, a marker associated with high triglycerides and low HDL. HDL or so-called "good cholesterol" are believed to be "garbage trucks" that clear the blood of harmful lipids, and are therefore advantageous.
You want high HDL, ideally greater than 60, and triglycerides below 150. But the actual numbers matter less than their ratio to each other. Both are brought on by high levels of dietary carbohydrates in comparison to fat.
The closer an HDL-to-triglyceride ratio is to one-to-one the better. Ideally you shouldn't have more than twice the triglycerides than you have HDL, and the ratio is considered the strongest predictor of coronary disease, with a TG/HDL of greater than 4 being "the most powerful independent predictor of CAD development," according to a Brazillian study of 374 patients in 2008.
With so many refinements on the cholesterol hypothesis, the notion of total cholesterol as a meaningful value has become something of an anachronism. By 2015, health officials finally acknowledged that eggs were fine to eat, a nod to the fact that the body produces far more cholesterol through its natural machinery than we could ever take in through our diet.
Meanwhile the focus has shifted during this period to two different biomarkers, HDL or so-called "good cholesterol," and triglycerides. The combination of low HDL and high triglycerides is known as "atherogenic dyslipidemia," is associated with greater prevalence of a small and dense LDL particle type and is a marker of inflammation.
Now the authors say this HDL-triglyceride ratio is also a marker of high risk for severe outcomes with COVID-19.