It says something about the author Danielle Steel’s work ethic that her desk, built to resemble a stack of her own books, is less remarkable than the hours she puts in at it. The 71-year-old romance novelist is notoriously prolific, having published 179 books at a rate of up to seven a year. But a passing reference in a recent profile by Glamour magazine to her 20- to 22-hour workdays – not to mention the 24-hour session “a few times a month, when she feels the crunch” – prompted an outpouring of awestruck admiration online.

“If she gets four hours, she considers it a restful night,” marvelled Business Insider. Elsewhere, the question “why Danielle Steel is more successful than the rest of us” was answered: “Steel does not understand this modern-day mentality of work-life balance”.

Steel has given that 20-22 hour figure when describing her “exhausting” process in the past: “I start the book and don’t leave my desk until the first draft is finished.” She goes from bed, to desk, to bath, to bed, eschewing all contact aside from phone calls with her nine children; “I do not comb my hair for weeks,” she says. Meals are brought to her desk, where she types until her fingers swell, her nails often bleed and “every muscle is shrieking”.

The business news website Quartz held Steel up as an inspiration, writing that if only we all followed her “actually extremely liberating” example of industrious sleeplessness, we would be quick to see results. Well, indeed. The National Sleep Foundation’s guidelines recommend that, at 71, Steel should be sleeping for seven to eight hours every night; the recommended duration for those aged 18 to 65 is seven to nine.

Taken in tandem with findings that show the cumulative effects of sleep loss, and its impact on judgment and productivity, doubt has been voiced as to the accuracy of Steel’s self-assessment. Her output may be undeniable, but sceptics have suggested that she is guilty of erasing the role of ghostwriters at worst; gross hyperbole at best.

Steel says working up to 22 hours a day is “pretty brutal physically” – but is it even possible? “No, in a nutshell,” says Maryanne Taylor of the Sleep Works. While you could work that long, especially as a one-off, the impact on productivity would make it hardly worthwhile. “The idea that someone could sustain that pattern effectively – work, write, commit things to memory, use their full brain capacity – is just unbelievable to me,” agrees Katie Fischer, another sleep consultant. If Steel was routinely sleeping for up to four hours a night, she would likely be drastically underestimating the negative impact of it, says Alison Gardiner, the founder of the sleep improvement programme Sleepstation. “It’s akin to being drunk.”

It is possible that Steel is exaggerating the demands of her schedule. Self-imposed sleeplessness has “become a bit of a status symbol”, says Taylor, a misguided measure to prove how powerful and productive you are. Margaret Thatcher was also said to get by on four hours a night, while the 130-hour work weeks endured by the former Yahoo! chief executive Marissa Mayer and other tech heads has been held up as key to their success.

That is starting to change with increased awareness of the importance of sleep for mental health. “People are starting to realise that sleep should not be something that you fit in between everything else,” says Taylor.

But it is possible – if statistically extremely unlikely – that Steel could be a “short sleeper”, born with a mutation in the gene regulating circadian rhythms. People with the mutation wake up after three to four hours’ sleep without an alarm, feeling fully alert without the need for caffeine or naps, says Dr Sophie Bostock of the sleep improvement programme Sleepio – but it is extremely rare. “It is probably present in fewer than 1% of the population.”

Even if Steel does happen to be among that tiny minority, says Bostock, it is “pretty irresponsible” to suggest that 22-hour days are simply a question of discipline for the rest of us. “It really does sound as though she’s got quite an unusual body clock.”