One habit could drive the risk of severe Covid-19 in young adults — study

Months of rapid-fire research during the Covid-19 pandemic means we know who stands the most to lose if they become sick. Anyone can get Covid-19, but generally speaking, the elderly or people with certain underlying health conditions face the most severe risk of disease.

Because of that, young adults — think people between 18 and 25 — may feel they're less susceptible to severe illness than other groups are. That's a dangerous way to think: Case reports, along with a new study, pinpoint how vulnerable that age group really is. In some cases, their vulnerability is boosted by an unhealthy, immensely popular habit.

Based on a sample of 8,405 adults between 18 and 25, scientists at the University of California San Francisco suggest that about 32 percent of young adults are "medically vulnerable" to severe Covid-19.

"Medically vulnerable" means that they check one of the CDC's boxes suggesting that they are at higher risk of getting very sick.

The study's first author is Sally Adams, a specialist at the University of San Francisco. She tells Inverse those boxes typically include conditions including, but not limited to, obesity, diabetes, asthma, or a weakened immune system.

One factor not listed by the CDC, however, seemed to be behind her results more so than the others, Adams tells Inverse. Her study was published Monday in The Journal of Adolescent Health.

Faced with research suggesting that smoking is linked to more severe Covid-19, Adams included the habit in her analysis. If you were to exclude smokers, only about 16.1 percent of young adults in her study were faced with risk of severe Covid-19.

"Smoking confers risk to a higher percentage of people."

It's not that smoking is a more powerful risk factor than underlying health conditions. It simply may be that smoking is a risk factor that turns up in more young adults who otherwise don't have other risk factors, Adams explains.

"Smoking confers risk to a higher percentage of people," Adams Inverse. "Young adults don't typically have a lot of chronic illness. But we were sort of surprised to see that actually 20 percent of the young adult sample had used some form of tobacco or E-cigarettes in the past 30 days."

That suggests it's time to see smoking as a risk factor for severe Covid-19 illness – even in younger people. Experts tell Inverse that vaping may pose risks too, though that picture is less clear due to a lack of data.

What do we know about smoking and Covid-19? – Panagis Galiatsatos is the director of the Tobacco Treatment Clinic at Johns Hopkins Medicine. He agrees that there's research suggesting that smokers do tend to do worse when it comes to Covid-19, but cautions that studies on tobacco are often plagued with inconsistencies (mostly stemming from the issues with self-reporting).

"The research we’re all interested in is what patients do worse?" Galiatsatos tells Inverse. "That’s how we discovered older age, high blood pressure, patients with diabetes. Smoking has, in the few studies that have captured it accurately, led to worse outcomes"

A small study on Chinese Covid-19 patients hospitalized in January suggested that smokers were 14 times more likely to progress to severe forms Covid-19 than non-smokers were. That study was followed by animal studies suggesting that smoking increases the amount of ACE2 receptors on the lungs – the very landing pad that SARS-CoV-2 needs to latch on.

Galiatsatos' own unpublished analysis (a report is upcoming) suggests that the risk of severe Covid-19 posed by smoking is less with those seen for other underlying health conditions, but still noteworthy.

In his analysis of 109 studies, he found that smokers, compared to nonsmokers, had a 43 percent increase in chance of death if they became ill with coronavirus. For comparison, those with diabetes had a 74 percent increase chance of death, he says.

While smoking doesn't pose the same level of risk as hypertension or diabetes, it's impossible to truly tease apart these results. Smokers are also 30 to 40 percent more likely to develop type II diabetes, reports the CDC.

At the end of the day, the habit can compounds existing risk — as well as be a risk factor in and of itself.

What about vaping? – Adams chose to include vaping in her estimation of risk for young adults because of indications that it may elevate the risk of severe illness.

"We added e-cigarettes because we could see that e-cigarettes have a lot of negative effects on the respiratory and immune system," she explains. The National Institute on Drug Abuse also agrees that e-cigarettes may diminish the lungs' ability to respond to infection.

Vaping has the same "biological plausibility" for making Covid-19 worse as smoking cigarettes, says Galiatsatos. Studies have suggested that vaping can decrease immune function, or lead to early indicators of lung damage.

Early studies also infer that vaping is likely adding to the risk of severe illness, says Galiatsatos. But studies that directly draw that connection are scant. That is likely a data problem — not evidence that such connections don't exist.

An issue with vaping is that not many doctors ask people if they have a vaping habit to start with, Galiatsatos says. If connections between the habit and severe outcomes exist they're often lost.

"In my own clinical experience, I'm one of the few doctors that ask about [vaping] explicitly," he says.

If there was ever a time for doctors to ask, and for patients to disclose that information, now might be it. Vaping remains one of the most commonly reported substance use habits amongst young adults, especially high schoolers.

Meanwhile, early indicators suggest that Covid-19 hospitalizations are trending younger in places like Miami. The CDC's nationwide Covid-19 hospitalization data shows that in May between 25.4 percent and 32.2 percent of hospitalized Covid-19 patients were between 18 and 49 years old. In June that jumped slightly to between 32 percent and 41.3 percent.

The relationship between those two trends — a steady flow of young vapers, and increase hospitalizations of young people — is still being untangled.

If you're asked about vaping specifically, be honest with a doctor, Galiatsatos suggests. Doing that might not just benefit you, but many other people in the future who find themselves fighting Covid-19.

Inverse is asking readers what pressing questions they have about Covid-19. Do you want to know how schools will reopen? What crucial next steps need to happen for a vaccine? Let us know what's on your mind, and we'll find the answer.

Partial Abstract:

Methods: A young adult subsample (aged 18–25 years) was developed from the National Health Interview Survey, a nationally representative data set, pooling years 2016–2108. The medical vulnerability measure (yes vs. no) was developed, guided by the Centers for Disease Control and Prevention risk indicators. The estimates of medical vulnerability were developed for the full sample, the nonsmoking sample, and the individual risk indicators. Logistic regressions were conducted to examine differences by sex, race/ethnicity, income, and insurance.

Results: Medical vulnerability was 32% for the full sample and half that (16%) for the nonsmoking sample. Patterns and significance of some subgroup differences differed between the full and the nonsmoking sample. Male vulnerability was (33%) higher than female (30%; 95% CI: .7–.9) in the full sample, but lower in nonsmokers: male (14%) versus female (19%; 95% CI: 1.2–1.7). The white subgroup had higher vulnerability than Hispanic and Asian subgroups in both samples—full sample: white (31%) versus Hispanic (24%; 95% CI: .6–.9) and Asian (18%; 95% CI: .4–.5); nonsmokers: white (17%) versus Hispanic (13%; 95% CI: .06–.9) and Asian (10%; 95% CI: .3–.8).

Conclusions: Notably, lower young adult medical vulnerability within nonsmokers versus the full sample underscores the importance of smoking prevention and mitigation.