Declines in non-HDL cholesterol levels, increased HDL cholesterol levels, decreased systolic blood pressure and smoking cessation could be just some of the reasons why patients in the U.K. saw a 74 percent decrease in incidence of MI, according to a 20-year follow-up of the Whitehall II cohort published online June 8 in the European Society of Cardiology. However, these rates could have been even lower, but the rise in body mass indexes (BMIs) stunted further improvement.
The aim of the current analysis was to evaluate the risk factor trends to 20-year declines in MI incidence in British men and women enrolled in the Whitehall II cohort. The Whitehall II cohort included 6,379 men and 3,074 women who were followed between 1985 and 2004 and for MI incidence and risk factor trends.
During the time span, 256 first MI events occurred during 107,892 person-years of follow-up. The average annual age-sex adjusted decline in MI hazard over the 20-year span was 6.5 percent, Sarah L. Hardoon, MSc, of the University College London Medical School, and colleagues found. This resulted in a decrease in incidence of MI of 74 percent, an aveage annual decline of 6.5 percent.
Five risk factors contributed to 56 percent of the MI decline: non-HDL cholesterol levels (30 percent), increased HDL cholesterol levels (17 percent), reduced systolic BP (13 percent), reduced smoking prevalence (6 percent) and increased fruit and vegetable consumption (7 percent).
However, rising BMI was “counterproductive,” the authors wrote, and adversely affected the decline in MI by 11 percent. The researchers speculated that MI decline could have been 8 percent greater without the rise of BMI.
Hardoon and colleagues noted that non-HDL cholesterol had the greatest impact on the decline of MI. “The favorable time trend in non-HDL cholesterol may reflect the increasing use of lipid-regulating medication or lifestyle (e.g. diet) or some combination of factors,” the authors wrote. “Statin use rose to 11 percent of the cohort (25 percent of those with high LDL cholesterol) by the end of the follow-up in 2004, suggesting that lipid-regulating medication may have made an appreciable contribution.
“In this cohort of London civil servants, there was a substantial decline in MI over two decades to 2004, more than half of which could be attributed to favorable risk factor trends, highlighting what can be achieved and emphasizing the value of measures to reduce exposure to these risk factors in the population,” the authors wrote.
Hardoon et al said that future research will be necessary to understand whether the residual unexplained portion of the decline in MI could be attributed to early treatment or other risk factors. The fact that there was no association of the decline in physical activity and time trend in MI could be a limitation of the study, the authors noted.
“While the negative contribution of rising mean BMI over recent decades appears to have been outweighed by the favorable trends in other vascular risk factors, continued increases in BMI may further reduce or even reverse the decline in MI incidence,” the authors concluded.
While statin use and BP-lowering medications may be feasible to administer in the U.K. and other countries, it may be difficult to achieve the same level of decline in incidence in MI in other emerging economies.