Four in five people have a heart age older than their real age, leaving them at risk of early death from cardiovascular disease, Public Health England data show.
The agency says its online Heart Age Test has now been completed more than 1.9 million times, and that in 78 percent of cases heart age was found to be higher than it should be.
The results show that 34 percent of people had a heart age more than five years above their real age while in 14 percent it was a decade older.
"Millions are at risk of cardiovascular disease but don't know it, putting themselves at real risk of suffering ill-health or dying younger,” Professor Jamie Waterall, national lead for cardiovascular disease at PHE.
"By making important lifestyle changes you can reduce your risk before it's too late."
According to PHE, 24,000 of deaths in England every year are in people aged under 75 years, and the vast majority of these - 80 percent - are preventable, which equates to around 50 per day.
The agency has now launched a campaign calling for adults across the country to take the free Heart Age Test and reduce their risk of cardiovascular disease with lifestyle/behavioural changes if necessary.
Dr Matt Kearney, national clinical director for cardiovascular disease prevention, at NHS England, said the test could potentially help millions of people.
“The long term plan for the NHS will prioritise saving lives through improved protection against cardiovascular disease, and increased public understanding of the risks of stroke and heart disease will mean fewer people have to face these devastating conditions,” he noted.