Risk Factors for Severe COVID-19: What Makes It Harder for Some and Easier for Others?

The way it’s reported, you’d think that susceptibility to COVID-19 severity is equally distributed across the world’s population. But when you compare case and mortality rates between countries, differences emerge. There are even differences within countries and states and cities. It’s clear that other variables besides simple exposure to the virus and infection are at play. Research continues to emerge regarding risk factors for severe COVID-19.

What are they?

And, more importantly, can you modify any of the variables?

Does Blood Type Predict COVID-19 Severity?

Early on, researchers noticed an apparent association between blood type and coronavirus infection. Those with A or B-type blood were more likely to be positive; those with type O were less likely to carry the virus.https://journals.lww.com/ccejournal/Fulltext/2020/06000/Gender_Difference_Is_Associated_With_Severity_of.26.aspx‘>² All 12 studies analyzed had similar results; there was very little heterogeneity.

Is this caused by sex, though? After all, from what I could tell, the meta-analysis failed to control for other variables that might have differed between the groups, like metabolic syndrome or obesity. And yet sex does play a role, even when a risk factor like obesity is accounted for. Other research confirms that overweight men are at greater risk for coronavirus severity than overweight women, for example, and we know from previous research that men and women have different types of immune responses to viruses and vaccines.https://journals.library.ualberta.ca/jpps/index.php/JPPS/article/view/31069‘>⁴

Verdict: Sex matters. Men are at greater risk.

Selenium Status and COVID-19

Early on, I noticed that selenium status plays a big role in susceptibility to a number of different viruses, including the flu, the original SARS, and many others. The viruses sequester selenium and utilize it to replicate and to weaken the host. Many of the original places where COVID-19 took hold had abysmal levels of soil selenium; this translates to lower levels of selenium in the food grown in the soil and a higher risk of population-wide selenium deficiency.https://www.mdpi.com/2072-6643/12/7/2098‘>⁶

Verdict: Likely. This hasn’t been proven to be causal, but it’s certainly trending in that direction. It can’t hurt to eat a couple Brazil nuts every day.

Can Adequate Vitamin D Improve Coronavirus Outcomes?

The earliest coronavirus hot spots were actually colder, cloudier spots with low UV-indexes. Wuhan, China, had a ton of cloud cover in January and always has a lot of air pollution which further blocks the UV light. Lombardy, Italy, also had pollution problems and UV index too low to produce much vitamin D. And now, studies are finally coming out lending credence to the idea that vitamin D protects against severe infection.

In Iran, COVID-19 patients with vitamin D levels above 30 ng/ml had a lower risk of severe infection and death.https://www.medrxiv.org/content/10.1101/2020.06.21.20136903v2‘>⁸

It’s not just vitamin D, of course. Vitamin D is more likely a marker of sun exposure, which confers a multitude of other immune and health benefits. One such benefit with known links to COVID-19 is nitric oxide. Another is normalization of the circadian rhythm. So don’t assume mega-dosing vitamin D supplements will protect you from COVID-19 as much as getting natural sunlight will. Most of these people probably weren’t supplementing (or even thinking about) vitamin D at all. They went into the infection with the levels they had.

Verdict: Aim for 30 ng/mL and above. Get plenty of sunlight.

Does Obesity Make You More Susceptible?

Obesity is an enormous complicating variable. It’s not just because obese people are more likely to be unhealthy in other ways, although that’s probably part of it. It’s because obesity itself is unhealthy. Body fat secretes more inflammatory compounds and promotes an elevated baseline of inflammation. The coronavirus damages your body in part by up-regulating those inflammatory compounds. If you’re starting with elevated inflammation, you’re making the virus’ job that much easier.

Sure enough, obesity is linked to COVID-19 severity.https://www.acpjournals.org/doi/10.7326/M20-3742#f1-M203742‘>¹⁰ Extreme obesity (BMI of 45+) is even worse, with some research suggesting it quadruples the risk of severe COVID-19.https://www.staradvertiser.com/2020/08/13/breaking-news/amid-covid-19-pandemic-people-with-diabetes-struggle-to-get-insulin/‘>¹² Among Chinese patients in another study, the mortality risk was 7.8% in those with diabetes and 2.7% in those without diabetes.https://pubmed.ncbi.nlm.nih.gov/32231171/‘>¹⁴

However, those hypertension patients taking ACE inhibitors had a lower risk of severity or death than those hypertension patients who were not being treated.https://www.nature.com/articles/s41586-020-2550-z‘>¹⁶ In another study, between 20-50% of unexposed people showed t-cell activity against COVID-19.https://pubmed.ncbi.nlm.nih.gov/32650004/‘>¹⁸

Both dietary omega-3s and omega-6s have been shown to strongly influence tissue levels of omega-3 and omega-6 and thus inflammatory/anti-inflammatory eicosanoid balance. My guess is that seed oil-eating people with elevated tissue omega-6s are at a greater risk for severe COVID-19 than people with more balanced omega-6:omega-3 tissue levels.

Verdict: We’ll see.

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Fermented Cabbage Intake

Most of the countries with low COVID-19 mortality rates have a long tradition of eating fermented cabbage. There’s South Korea with kimchi and the Balkans and Central Europe with sauerkraut. And in a recent study, researchers found that fermented cabbage intake predicted low COVID-19 mortality.