The overall fall in deaths from coronary heart disease in Britain masks a slow down in deaths in middle aged adults, pointing to a "disquieting" trend, indicates research published ahead of print today. 
An assessment of death rates for coronary artery heart disease in England and Wales between1984 and 2004, grouped by age, shows impressive falls, overall. .
The decline was almost 55% among men and 48% among women over the two decades.
The average annual decline in heart deaths steadily increased every decade to reach almost 5.5% for men and over 4% for women from 2000 onwards.
But death rates from heart disease among younger Britons were lower and appear to be levelling off.
For 35 to 44 year old men the decline in death rates was 35%, and for those aged 45 to 54 it was 47%.
And between 2000 and 2004, there was virtually no fall in death rates from heart disease among those aged between 35 and 44.
In 45 to 54 year old women, the annual decline in death rates was 38%, and while rates in those aged 35 to 44 continued to fall, the numbers of heart attacks were few.
Lifestyle changes and effective treatments have made steady inroads into the death toll from coronary heart disease have been since the late 1960s.
But rising trends in obesity and diabetes threaten to halt or even reverse the "hard fought gains" in cutting deaths from heart disease, warn the authors.
These trends are much more likely to emerge among younger Britons first, they say and mirror the experience of the United States, where rates of obesity and diabetes are also soaring.
"The party is over, and complacency runs a high risk," they conclude. "The flattening trends in [coronary heart disease] mortality rates among younger adults suggest that the cardiovascular disease epidemic is not being controlled."
Figures released from the British Heart Foundation today as part of its "Doubt Kills" campaign show that around a third of heart attack patients die before they reach hospital, often because they fail to recognise the symptoms in time.
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Over the past decade over 1.2 million people have lost their lives to heart attacks.
The figures show that there were in excess of 100,000 deaths from coronary heart disease in 2005, almost all of which would have been heart attacks., making this the UK's single biggest killer.
Scotland remains the UK's heart attack hotspot, with a premature death rate 70% higher than the South West of England for men, and 88% higher for women.
Coronary heart disease trends in England and Wales from 1984 to 2004: concealed levelling of mortality rates among young adults.
Online First Heart 2007 doi:10.1136/hrt.2007.118323