MI Risk Higher in Apple-Shaped Women Than Men

Patrice Wendling

March 02, 2018

A new study provides further evidence that higher waist size and waist-to-hip ratio signal a greater risk for myocardial infarction (MI) than general obesity, especially in women.

Compared with body mass index (BMI), waist-to-hip ratio was an 18% stronger predictor of MI in women and a 6% stronger predictor of MI in men.

"The general message is that excess weight matters but that women who indeed have an apple shape might be at an even greater risk. So it's about increased awareness not only among the women themselves but also among physicians," study author, Sanne AE Peters, PhD, from the George Institute for Global Health, University of Oxford, United Kingdom, said in an interview.

"One might argue that we need more intensive screening, particularly among women with an apple shape, to try and really identify their increased risk of heart disease and, for example, to start interventions whether they're lifestyle interventions to lose weight or to start other preventive strategies," she added.

Peters noted that previous studies have indeed shown that central adiposity might be a stronger risk factor than overall obesity, but there have been studies that have shown the opposite — that it actually does not matter where adiposity is measured.

"The critical new thing in our work is that we've looked at sex differences between both central and overall adiposity and the risk of heart disease and what we found is that central adiposity is actually an even stronger risk factor for heart disease in women than in men," she said.

The study, published online February 28 in the Journal of the American Heart Association, involved 265,988 female and 213,622 male participants aged 40 to 69 years (mean, 56 years) in the prospective UK Biobank study between 2006 and 2010. Exclusion criteria included a history of cardiovascular disease or BMI less than 15 kg/m2 or greater than 60 kg/m2.

Participants completed questionnaires on their lifestyle, environment, and medical history and had blood, urine, and saliva collected. Physical measurements included weight, height, hip circumference, waist circumference, and waist-to-hip ratio.

At study entry, the mean waist circumference, waist-to-hip ratio, and waist-to-height ratio, respectively, were 85 cm (33.46 inches), 0.82, and 0.52 in women and 97 cm (38.18 inches), 0.93, and 0.55 in men.

During a mean follow-up of 7.1 years, there were 5710 MIs, of which 28% were in women.

In both sexes, there was an approximate log-linear relationship between measures of general and central adiposity and the risk for incident MI.

In Cox regression models, a 1–standard deviation increase in BMI was associated with a hazard ratio (HR) for MI of 1.22 in women (95% CI, 1.17 - 1.28) and 1.28 in men (95% CI, 1.23 - 1.32; P for interaction = .15).

A 1–standard deviation higher waist circumference was more strongly linked with MI risk in women than in men, although the difference just reached statistical significance (P for interaction = .048). The HR was 1.35 in women (95% CI, 1.28 - 1.42) and 1.28 in men (95% CI, 1.23 - 1.33).

The association was even stronger with an increase of 1–standard deviation in waist-to-hip ratio, with an HR for MI of 1.49 in women (95% CI, 1.39 - 1.59) and 1.36 in men (95% CI, 1.30 - 1.43; P for interaction = .001).

Finally, the link between a 1–standard deviation higher waist-to-height ratio and the risk for MI was similar between women (HR, 1.34; 95% CI, 1.27 - 1.40) and men (HR, 1.33; 95% CI, 1.28 - 1.38; P for interaction = .38).

Gina Lundberg, MD, a preventive cardiologist from Emory University in Atlanta, Georgia, who was not involved in the study, said the results aren't that surprising because it's known that metabolic syndrome, which includes a waist circumference over 40 inches for men or 35 inches for women as one of its five criteria, is more common in women than men, and more dangerous. 

"To me the little pearl here is when clinicians are seeing women, particularly when they're going from 45 to 55 and are gaining weight or they feel they're gaining it in the abdomen, to not just dismiss it like, 'Oh, that's benign,'" because it isn't benign," she said. "The waist-to-hip ratio is important, it is a marker for increased heart disease — and it may be that if we can't help the woman lose weight in the belly, we need to pay a little more attention to the blood pressure that's not ideal or to the cholesterol that's not ideal, and make sure we're aggressively following all of her risk factors."

Some diets, including low-carbohydrate diets, have been promoted as helping shed excess belly fat, but Lundberg said we've yet to crack the mystery of how to lose weight in specific body regions.

"But I do think that an overall plant-based, calorie-appropriate diet with the 30 minutes a day of exercise, whether it's 10 minutes 3 times a day or continuous, is the healthier lifestyle pattern that we should be employing with our patients," she said.

Both Peters and Lundberg point out that one of the practical considerations with tracking central adiposity is that it can be difficult to determine exactly where to measure waist circumference, particularly in those who are severely obese.

"Our study protocol said it had to be measured at the naval," but "whatever you decide it should be consistent and should be at a predefined point because otherwise you can't track changes over time or waist-to-hip ratio from one individual to another," Peters said.

As to the biological basis for women's excess MI risk associated with central adiposity, the investigators note that genome-wide association studies of fat distribution have identified several genes with a stronger effect in women than in men that are known to be associated with other metabolic pathways, including lipid traits and insulin resistance.

Additional insights into adiposity may be gained from the UK Biobank, which is collecting large amounts of data on body fat distribution by using MRI.

"Ultimately what we want to do is to move beyond just the tape measure and the scale and the height measure to use, for example, imaging-derived measurements of body fat distribution to actually classify patients into very specific body shapes and body fat distributions," Peters said. "Because even if you're a person with an apple shape, it may be that the way the fat surrounds the organs, surrounds the liver, surrounds all the critical places in the body, those differences will still be there and that's something you can't quantify using just a tape measure."

Peters is supported by a UK Medical Research Council Skills Development Fellowship. Lundberg reported no financial disclosures.

J Am Heart Assoc. Published online February 28, 2018. Abstract

Follow Patrice Wendling on Twitter: @pwendl. For more from theheart.org | Medscape Cardiology, follow us on Twitter and Facebook.

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