More than 20 million Americans ages 60 to 65 got a rude surprise this year. Many of us, BC — before the novel coronavirus — had counted on a little more time before we had to see ourselves as “old”.

Yet in recent weeks, we’ve been shoved towards senescence as supermarkets have scheduled “senior hours” for those 60 and older, and major media have reported experts’ warnings that the elderly, starting at age 60, are extra vulnerable.

Suddenly 60 is the new 65. At 62, I believe I speak for many other late-stage boomers when I say: “Wait, what?”

“I turn 60 later this year, so I noticed that acutely,” said Chip Conley, founder of the Modern Elder Academy, which he calls the world’s first midlife wisdom school. “It was all of a sudden, I’m in a high-risk group? I’m perceived as elderly?”

I don’t mean to reject any help that may keep me and my greying cohort alive. Bring on those peaceful senior shopping hours. Nor would I ever argue that policing these linguistic limits should be a top priority when thousands of Americans have died, tens of millions are out of work and our democracy is floundering.

All the same, this sudden downward pressure on the boundary of old age strikes me as un-American. The Centres for Disease Control and Prevention and the Census for years have used 65 to define older Americans. (It was only last Thursday that the CDC tried to calm the confusion with a press release stating: “It’s not just those over the age of 65 who are at increased risk for severe illness.”)

You still can’t get Medicare until 65 or full social security benefits until age 66. So maybe this is something else we can blame on China and the World Health Organisation, given that both use “over 60” to define old age, and both have been the source of a lot of coronavirus news. More important, for those of us in the early-sixties grey zone, the slipping standard harms more than our vanity, stealing our last shred of deniability even as the shutdown deprives us of tools we have relied on to pass ourselves off as younger, such as Botox, hair salons and gyms.

Denial plays a vital role in human survival, which helps to explain why most prefer to bask in it as long as possible.

“From age 40 onwards, people report feeling about 20 per cent younger than their chronological age, an amount that obviously gets bigger over time,” Sarah Barber, an expert on cognitive ageing at Georgia State University, told me.

As we age, we also tend to imagine “old age” as beginning later and later, she said, further boosting our illusion that we are still young.

We’re only as old as we feel, as they say. The hitch is we can be made to feel older — and frailer and less competent — when reminded of our age and the inevitable downsides. This has been established by studies of the “stereotype threat”, meaning that when old people, or mothers, or other groups, for example, are reminded of the stereotypes about their group, they unwittingly tend to validate them.

In one seminal study, older adults — in this case ages 62 to 84 — were split into three groups. One group read articles linking age to cognitive decline. Another read articles describing older people who stayed sharp as they aged. The third group did no reading. All three groups then took a test that challenged them to remember several words. Guess which group forgot most of them? The first one, of course.

Focusing on gloomy images of ageing can make you less co-ordinated and even less healthy. Researchers have found that people who feel more negative about ageing in midlife may be later less competent drivers and have a harder time recovering from a heart attack. People who accept the most depressing cultural images of ageing may also take worse care of themselves, even shortening their own lives by an average of 7½ years.

Pandemic culture floods us with constant reminders about ageing and death, not least with its nasty Twitter hashtags such as BoomerDoomer and BoomerRemover. Stories about “seniors” are frequently illustrated with images of stooped postures and canes, or photographs of lonely, white-haired grandmothers peering out of locked windows.

No wonder my knees ache and I’ve recently switched to stronger reading glasses. More than once, I’ve asked my husband what day it is, which is unsettling for both of us, as much as I’ve heard other age groups are having the same trouble.

Seeking to stop stereotypes from becoming self-fulfilling prophecies, groups such as Conley’s Modern Elder Academy and the AARP — formerly known as the American Association of Retired Persons — have been trying to “reframe” ageing, emphasising the many purported benefits, such as wisdom and contentment. They are casting a wide net, given that the average age of Conley’s “elders” is 52, and the AARP starts mailing you membership cards when you turn 50.

Ageism has long been one of America’s favourite prejudices, even though — if we’re lucky — we will all become its target. “We disparage elderly people without fear of censure,” wrote the psychologist authors of a study on ageing stereotypes, “Doddering but dear.”

Among other discouraging news, they cite research demonstrating that on top of discrimination in hiring and medical decisions, older adults are more likely than any other age group to appear on TV and in movies “as conduits for comic relief, exploiting stereotypes of physical, cognitive, and sexual ineffectiveness”.

No wonder even many in the over-65 set don’t feel ready for the new considerations and limitations based on being officially over the hill.

“I feel grounded like a wayward adolescent punished for underaged smoking or drinking,” complained Politico editor Paul Taylor, 65, referring to his cohort of “fit, never-been-busier, un-retirees” as “the twelderly,” inspired by the word “tween”, for a preadolescent.

Before the pandemic, I, too, imagined myself as, at worst, pre-elderly, while assuming there was widespread agreement about the endpoint of plausible youth. I’ll even confess to a shimmer of schadenfreude on reading Texas lieutenant-governor Daniel Patrick’s controversial call for old people to consider sacrificing their lives for the economy, given that Patrick’s standard was “70-plus”.

But then I realised just how much the coronavirus may be infecting all of us with the most dreadful view of ageing, in which “old” is synonymous with useless and expendable.

And who’s ever ready for that?

• Katherine Ellison’s latest book is Mothers & Murderers: A True Story of Love, Lies, Obsession ... and Second Chances