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Researchers on Monday announced the most comprehensive estimates to date of elderly people’s elevated risk of serious illness and death from the new coronavirus: Covid-19 kills an estimated 13.4% of patients 80 and older, compared to 1.25% of those in their 50s and 0.3% of those in their 40s.

The sharpest divide came at age 70. Although 4% of patients in their 60s died, more than twice that, or 8.6%, of those in their 70s did, Neil Ferguson of Imperial College London and his colleagues estimated in their paper, published in Lancet Infectious Diseases.

The new estimates come as scientists have been scrambling to figure out the underlying reasons for older people’s greater susceptibility to the virus — and, in particular, why some mount a stronger immune response than others.

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It starts with preexisting conditions: Data from China show that such comorbidities dramatically raise the risk of dying from Covid-19. But chronic illnesses may be not only a contributor to Covid-19 deaths but also a mark of biological aging and declining immunity.

“It is not chronological age alone that determines how one does in the face of a life-threatening infection such as Covid-19,” cautioned geriatrician and gerontologist George Kuchel of the University of Connecticut. “Having multiple chronic diseases and frailty is in many ways as or more important than chronological age. An 80-year-old who is otherwise healthy and not frail might be more resilient in fighting off infection than a 60-year-old with many chronic conditions.” Reason: She may have a younger immune system.

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The new calculations, based on 70,117 laboratory-confirmed and clinically-diagnosed cases in mainland China and 689 cases among people evacuated from Wuhan on repatriation flights, allowed the Imperial College researchers to estimate the overall death rate from the disease. In the outbreak’s early weeks that was thought to be as high as 3% to 8%. Instead, the fatality rate among people with confirmed disease is 1.38%, they concluded.

That supports an estimate by researchers at the Harvard T.H. Chan School of Public Health earlier this month of a 1.4% fatality rate in confirmed cases.

The British group said the fatality rate among all of those infected with the new coronavirus — including those who don’t have symptoms — is 0.66%. By comparison, that is more than 30 times greater than the death rate for the H1N1 influenza, the cause of a 2009 pandemic, which was 0.02%.

The chance that a Covid-19 patient would develop symptoms severe enough to require hospitalization, especially for respiratory support, also rose sharply with age, Ferguson and his colleagues reported. In patients 80 and older, 18.4% did. While 12% of people in their 60s required hospitalization, 3.4% of 30-somethings and 1.1% of 20-somethings did. The sharpest difference came in late middle age: 4.3% of people 40 to 49 with Covid-19 required hospitalization, while 8.2% of 50-somethings did.

That is partly why the situation in Italy is so disastrous, with many hospitals overwhelmed by Covid-19 cases: The country’s median age (47) is the highest in Europe, and 23% of its people are 65 or older. Last week, doctors in Italy reported in the Journal of the American Medical Association that as of mid-March, 7.2% of Covid-19 patients had died. That might be partly explained by the high rates of infection among the elderly: 38% of Italy’s Covid-19 cases are in people 70 and older, compared to 12% in China.

The explanation for the generally heightened risk to the elderly, but also for the fact that Covid-19 kills many younger people even as some seniors survive, lies in a growing understanding of “immunosenescence.” Immunologists have identified some of the specific ways the immune system changes with age, allowing them to go beyond the simple assertion that it weakens.

“Older people are not as good at reacting to microorganisms they haven’t encountered before,” said physician and immunobiologist Janko Nikolich-Zugich of the University of Arizona College of Medicine. He calls it “the twilight of immunity.”

Our immune systems have two sets of defenses against viruses and other pathogens: a first-line army of cells, called leukocytes, that attack invading microbes within minutes to hours, and a second-line force of precisely targeted antibodies and T cells that surge to the battle front as late as several days after.

With advancing age, the body has fewer T cells, which produce virus-fighting chemicals. By puberty, the thymus is producing tenfold fewer T cells than it did in childhood, Nikolich-Zugich said; by age 40 or 50, there is another tenfold drop.

That leaves the body depleted of T cells that have not yet been programmed to defend against a specific microbe. Fewer such “naïve T cells” means fewer able to be deployed against a never-before-seen microbe.

“We just have fewer soldiers dealing with attackers we’ve never experienced before, like the new coronavirus,” Nikolich-Zugich said. (The body does retain the “memory T cells” that learned to fight attackers in youth, which is why immunization against smallpox and many other viral disease lasts decades.)

Another age-related change keeps T cells away from battle. Even before T cells enter the fray, other cells recognize invaders and dispatch natural killer cells and other soldiers to destroy as many as possible in the first few hours after infection. Then these same front-line cells literally show the virus to T cells, saying in essence, this is the enemy; produce virus-killing compounds.

“But this communication doesn’t work as well as we get older,” Nikolich-Zugich said. The instructor cells grow scarce and start to do the biological equivalent of mumbling. T cells therefore respond too late and too little.

Antibodies are made by B cells, and their decline is less precipitous than the fall-off in T cells. But old B cells, like old factories, can’t produce as much of their product — antibodies — as when they were new. Specifically, they have lower levels of the molecule that rearranges their genome so as to produce never-before-seen antibodies to a never-before-seen virus.

As if old age weren’t cruel enough, it brings one more change to the immune system: It slows down how quickly natural killer cells and other first responders hand off the defense to activated T cells and B cells. “This initial response remains in overdrive,” Nikolich-Zugich said. The core of that response is a fusillade of inflammatory molecules called cytokines.

That fusillade attacks the lungs and causes acute respiratory distress syndrome (ARDS), a common cause of Covid-19 deaths.

The cytokine barrage varies somewhat by sex, however. In a study published last month, Kuchel and colleagues showed that older men had, on average, more cytokine-producing cells than older women, who had more and better B cells and T cells.

That might explain the apparent, but still tentative, sex-based differences in the Covid-19 epidemic, with elderly men generally faring worse than elderly women. Hobbled B and T cells leave the body with fewer anti-coronavirus defenses.

Immunosenescence spells bad news if the new coronavirus continues to circulate, even at sub-pandemic rates, because it suggests that older people who have survived Covid-19 may not have robust immunity should they be exposed to the virus again.

With the flu, younger people have a stronger “immune memory” than older people — their T cells and B cells primed to attack if a flu virus they contracted decades ago returns. If immune memory for coronavirus resembles that for flu, Kuchel said, then “young people will be much more protected when it comes back.”

  • Layman here, 62, very grateful for the reporting in this article and on this website generally.
    Please keep it coming.

  • It seems as if a journal called Stat News would develop a better case before estimating mortality rates for this virus. It is unclear how these percentages were derived. If they are based on the number of deaths for each age group divided by the number of confirmed cases for each age group, then they are meaningless. If they are derived or adjusted using data from random sampling, which reveals that the majority of infected people show no symptoms, then please explain! Good grief.

    • I am not trying to be a regular on this comment board so this will be my last one.

      It seems to me you are confusing two different things.

      The death rate by age group (for those who are infected) is what the article was referencing and that is indeed the number of deaths / the number infected considered for selected age ranges is just that. This has been widely published in a number of places and shows as it does here that the older one is, everything else being equal, the greater the percentage of deaths. Add in things like chronic health conditions like heart disease or diabetes, which are more common with age, and it gets even worse.
      Try informationisbeautiful.com for a great infographic.

      If you want to estimate the infection rate of CV by age in the general population of any country then you would need data from reported cases. But since it is believed that many mild cases go unreported a more accurate estimation would be testing among a random sample of the population. I don’t think many are doing that right now but countries that have tested a large portion of their population would have a reasonable estimate of that by any number of demographic categories.

    • I believe in a national emergency we cannot wait for several more months or even years to get the “perfect, peer-reviewed, published study of the Wuhan virus workings on the human immune system”, and why death and hospitalization rates are different.
      The perfect is the enemy of the good information the public needs RIGHT NOW even if it is tainted with incorrect info.
      Educate the public that they need to weigh the source of any pandemic information. Beware especially of the “lone expert scientist or MD” pushing things they have a financial interest in, or media people hyping the fear for better ratings and more money they will be paid as a result.

  • I am nearly 78 and have had long term but well controlled diabetes. I’ve never smoked and I’m normal weight. But by any criteria I have a much greater risk than average for being hospitalized and dying if infected with COVID.

    But here is my complaint. All that is ever emphasized in these stories is death rate, not survival rate?

    There is an over 80% chance I won’t be hospitalized. There is an 87% chance if I am hospitalized I won’t die. Those are pretty good odds for anything in life. Why don’t you and all the others in the media put some perspective on this instead of implying this is as grim as the Black Plague and a guaranteed death sentence?

    • Those look like good odds on paper but when you take into account the extremely poor healthcare infrastructure in place, those odds don’t look so good. Just look at Italy and New York. I don’t see this article painting this as a guaranteed death sentence when it focuses mostly on numbers and the reasoning behind those numbers? Where do you get that from this article?

    • I am referring to the overall statistics. Are you in Italy? What about South Korea or Japan, which has an even older population than Italy yet a very low death rate period? The odds are the odds and math is math, which is about as real as anything can get. If you want to focus on the worst places, or the worst situations exclusively be my guest.

      My point, was and is, that the exclusive focus and attention to the death rate ignores that it is relatively low, even for the oldest individuals who contract the disease and are hospitalized. Therefore rather than living in constant fear and anxiety about getting this and dying, as so many are doing, a true realist would says the odds of survival are on my side no matter what my age, especially if I take all the reasonable precautions advised.

      If you chose to feel and think differently that is certainly your choice but one many of us care not to follow.

    • I am 62 and have some risk factors. With the originally reported 4.5 % death rate among men overall and worse the older you are, and having some added risk figures, and the fact China’s government is so dishonest – and the fact they locked down an entire province at what must be a huge cost – I figured the death rate could be much higher than 4.5% .
      Additionally, getting so sick you have extensive lung damage, which will take years to heal – I think it made sense to be pretty scared of it. It is starting to sound much less scary now, but only if you throw out the old numbers – but does that really make much sense?
      I want to wait until a wealthy democracy known for not lying much is at least 2 months into it’s epidemic and can get a good idea of everyone who had it at the beginning, then look at the deaths to figure the fatality rate. I do not trust China, and it’s too early to assess anywhere else.

    • It’s certainly too early to state anything about death rate in Japan. Their initial firewall approach didn’t work and their relatively low testing rate (118/million as of 03/28) means that the numbers may be an underestimate. South Korea’s rates are more believable considering the extensive testing they are conducting. The death rate is what is important because it correlates with hospitalization rates, which correlates with available resources, hence flattening the curve.

      Nowhere have I seen this being painted as the Black Death in this article, could you please point out where you saw this? The current death rates and hospitalization rates are important to know because we have to ensure we do not overwhelm limited health resources. That’s the realist in me understanding the actual situation.

  • Aren’t there ways we can strengthen our immune systems via diet and certain vitamins? For example, Vitamin C has been shown to strengthen the immune response to certain colds. Vitamin D3 has similarly been shown to improve immunity to certain diseases. Moreover, a healthy gut has been tied to improved immune function. I’m curious why these factors aren’t at least acknowledged in this and other articles related to Covid-19 and age/immune function.

    • Vitamin C has been studied for many years as a possible treatment for colds, or as a way to help prevent colds. But findings have been inconsistent. Overall, experts have found little to no benefit from vitamin C for preventing or treating the common cold (webmd)

      The only proven benefit of vitamin D is its role in helping calcium build strong bones. But that’s far from the whole story. Vitamin D helps regulate the immune system and the neuromuscular system. Vitamin D also plays major roles in the life cycle of human cells. (webmd)

      Vitamin C only has it’s rep because of Linus Pauling. Now if you have scurvy we can talk about upping your vitamin C intake otherwise you just pee out the excess. Vitamin D is a little murkier beyond bones and and nerves so I will give you that one. Your strongest point is the microbiome of the gut. That is the secret we have yet to tease out.

  • Layman seeking information here:
    The numbers cited for the decrease in T cells, going down by 90% once and then 90% again by certain ages, ages where a person generally remains healthy, and where men are still fertile, to me suggest the decline is adaptive, or mostly adaptive. If it was really maladaptive i would think our bodies would keep on making them.
    But, apparently it is not a good thing when you have an infection to fight.
    Is it worthwhile doing something to boost the numbers in advance? Like, have your blood drawn, concentrate the T cells, stored, and then re-infused if you get a serious infection?
    Should old folks be doing that now? ????

  • See: Vagus Nerve stimulation and tonification via Diaphragmatic belly breathing. Anti-inflammatory, anti-anxiety, anti-depression. Simple, easy, cheap as it gets, DIY at home remedy. Main reasons for Non-adoption/Compliance? People are lazy and unwilling to make even slight behavior modifications until they are nearly dead (not even then oftentimes), and MDs and the parasitic Sick Care System and Insurors MAKE NO MONEY. Plain and simple, yet such difficult medicine to take, apparently.

    Chris Anderl, Ph.D (piled higher and deeper) Psychology

    • The insurors lose (or make less) money when someone becomes sick, but would not exist at all if no one ever became sick. Healthcare and Medical Doctors came into being because sick people need diagnosis and appropriate care and treatment, but they are now also focusing on helping people avoid becoming sick (updating vaccinations, monitoring health status through routine wellness checks and laboratory testing). Without the insurers, few of us could afford our medical care. As it is now, the poor cannot afford either health insurance or their medical care, except that the really poor can get poor medical care free, but the less poor (the lower middle class) can’t afford insurance and can’t get medical care free, and can’t afford to pay for it, when critically needed. There is really no evil villain in this situation. It is just the way that human beings are “wired”. The solution seems to be to tax the “billionaires” to subsidize the insurance for people who can’t pay ‘full-freight”.

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