Heart disease death rates have been falling since the 1970s
Fears are being raised that rising levels of obesity and diabetes may be affecting the fall in heart disease death rates in women aged under 50.
Researchers from Oxford and Liverpool universities believe death rates among that age group may be plateauing after continuous falls since the 1970s.
They studied all deaths in England and Wales from 1931 to 2005 and found the pace of the drop had started to slow.
The team said the findings, in the BMC Public Health journal, were disturbing.
Heart disease death rates for all age groups increased until the 1970s, but have been falling continuously since.
This has been put down to better treatment and a fall in the number of people smoking.
However, the rate of the fall among women under 50 has started showing signs of slowing in contrast to the continuing increase in decline seen in older people.
For example, the death rate in the 45-49 age group nearly halved from the rate it was between 1976 and 1985 to 15 deaths per 100,000 between 1986 and 1995.
But in the 10-year period starting in 1996, it fell only to 12.5 deaths per 100,000.
Report author Peter Scarborough said: "What we may be seeing with the figures for women is a plateauing and in the future it may even rise.
"It seems to me that the increased rates of obesity and diabetes are playing a role in this and if this pattern is emerging in women then it is quite likely we will see the same in men in the future."
The report pointed out that obesity and diabetes levels have been rising in younger age groups over the last 10 years, while physical activity levels have fallen.
However, Mr Scarborough also admitted that as the number of deaths in the younger age groups was relatively small, it was hard to draw accurate conclusions.
Professor Peter Weissberg, medical director for the British Heart Foundation, which helped to fund the study, said the findings were "worrying".
"It's a common misconception that heart disease is a male problem, yet cardiovascular disease is the biggest cause of premature death in women.
"Heart disease should be a very real issue for all women, and younger generations must take action now to cut down their risk."