BMJ: Acute MI mortality decreases in the U.K.

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Acute MI (AMI) mortality declined between 2002 and 2010 in the U.K., and researchers attributed more than half of the decline to a reduction in event rates, while less than half was attributed to improved survival at 30 days, according to a study published in the Jan. 26 issue of the British Medical Journal.

"Declines have been observed in population-based mortality rates from coronary heart disease and acute myocardial infarction in many developed countries, including England, since the 1970s," Kate Smolina, a PhD candidate at the Department of Public Health in Headington in Oxford, England, and colleagues wrote.

To better understand the trends of event and fatality rates for acute MI, Smolina et al conducted a population-based study between 2002 and 2010 that included 840,175 people who were admitted to the hospital for acute MI or died suddenly from acute MI in the U.K.

The authors reported AMI event rates, 30-day mortality and total mortality. Of the AMIs, 61 percent occurred in men, 36 percent were fatal and 73 percent occurred in patients over the age of 65.

According to the authors, the age-stratified total mortality rate was cut in half over the study period, while age-stratified event and case mortality rates declined by one-third. The AMI event rate in men declined by 4.8 percent, and case fatality dropped 3.6 percent. Total mortality rates for men decreased 8.6 percent.

These corresponding figures for women were 4.5 percent, 4.2 percent and 9.1 percent, respectively. When the researchers compared data from 2002 to 2010, they reported AMI event rates dropped by 33 percent in men and 31 percent in women. However, the greatest declines of AMI events were seen in men and women between the ages of 65 and 74 and lowest in men and women between the ages of 30 and 54 and 85 years and older.

In terms of 30-day case mortality, from 2002 to 2010, age-standardized case fatality for AMI decreased from 42 percent to 32.1 percent in men and from 42.2 percent to 29.9 percent in women. When comparing 2002 to 2010, mortality rates fell 50 percent in men and 53 percent in women.

“The event rate played a slightly bigger part than case fatality in six out of nine regions, accounting for just over half of the decline in mortality,” the authors wrote. “Notably, the reductions in case fatality explained two thirds of the decline in deaths from acute myocardial infarction in London.”

The researchers called the annual decline of event rates “not statistically significant” for men and women ages 30-54 and those 85 and older. However, the researchers said that rising rates of obesity and diabetes in young people could have contributed to the plateau seen in AMI event rates. Additionally, the researchers said the lack of decline could have resulted from a shift in the first presentation of disease from middle to older age.

“Overall, just over half of the decline in deaths from acute myocardial infarction can be attributed to a reduction in event rate and just less than half to improved survival at 30 days,” the authors wrote. “However, the drivers behind declining mortality rates differ by sex, age and geographical region.”

“Three decades ago, mortality from coronary heart disease in the United States, which had been high since the Second World War, was found to be falling," Hugh Tunstall-Pedoe, of the University of Dundee, Ninewells Hospital in Dundee, Scotland, wrote in an accompanying editorial. “The reasons were obscure.

"As the world population ages and becomes more industrialized and urbanized, the decline in coronary mortality is predominantly in rich nations, while rates increase in dozens of others," he wrote. Tunstall-Pedoe offered that better data must be put forth from countries where the rates of coronary disease are increasing. However, he said that the motivation to conduct such studies may be "scarce."