Rising adiposity curbing decline in MI incidence
MedWire News: Risk for myocardial infarction (MI) has decreased by nearly 75% over the past 20 years in the UK, but the rising obesity rate may reverse this trend in the future, study findings suggest.
Over half of the decline in risk for MI can be accounted for by favorable changes in coronary risk factors, such as declining non-high-density lipoprotein (nonHDL) cholesterol levels and reduced systolic blood pressure, report the researchers in the European Heart Journal.
However, rising body mass index (BMI) appears to be countering these improvements, reducing the scale of this decline, they say.
Using data from the Whitehall II cohort - a 20 year follow-up study of over 10,000 male and female British civil servants - Sarah Hardoon (University College London Medical School, UK) and co-authors estimated the contribution of coronary risk factors to trends in the incidence of coronary heart disease between 1985 and 2004. Study participants were aged between 35 and 55 years at baseline and were followed up for a mean period of 15.4 years.
Hardoon and colleagues found that the age and gender-adjusted risk for MI fell by 74.0% from baseline, corresponding to an average annual decline of 6.5%.
Four risk factor trends contributed in isolation to this decline, namely declining nonHDL cholesterol (34%), rising HDL cholesterol (17%), declining systolic blood pressure (13%), and declining cigarette smoking (6%). Together these trends explained a total of 54% of the decline.
Increased fruit and vegetable consumption made a nonsignificant contribution of 7%, and when combined with the four other risk factors, explained 56% of the decline.
Over the study period, mean BMI increased by 0.1 kg/m2 per annum. This reduced the amount of MI risk reduction that was explained by the combined risk factors by 11%, from 56% to 48%.
Commenting on these findings, Hardoon et al say that "this suggests that the MI decline could be 8% greater in the absence of rising BMI."
They add that had other risk factor trends not occurred, "rising BMI may have led to an increase in MI incidence over the follow-up."
The team notes that risk factor trends were comparable for both men and women. This suggests that similar influences have operated for both genders, and, therefore, similar prevention strategies may be appropriate.
The researchers say: "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."
They conclude that rising BMI in the UK and in other countries needs "urgent attention."
MedWire (www.medwire-news.md) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011
By Nikki Withers