How good is waist-hip ratio as a predictor of cardiovascular risk?

How good is waist-hip ratio as a predictor of cardiovascular risk?

Body mass index (BMI) is an often used marker of obesity as it is simple to calculate and classify obesity. But it has its own limitations as a sole marker of obesity related cardiovascular risk. It does not capture the differential effects of adiposity in different parts of the body. BMI does not differentiate between subcutaneous and visceral adiposity. Nor does it distinguish between fat mass and fat-free mass. Fat free mass is known to have a strong inverse relationship with morbidity and mortality.

Hence the search for other parameters of obesity in relation to cardiovascular risk. Other measures used in this context are waist circumference and waist-hip ratio. Increase in the waist circumference would indicate more of visceral fat deposits, though subcutaneous fat deposits over the abdomen also contributes to increase in waist circumference. Increase in waist circumference indicates central obesity. Waist circumference measures abdominal or upper body size while hip circumference measures gluteofemoral or lower body size. Hip circumference measures both adipose tissue and lower body muscle mass. A thigh circumference below 60 cm has been associated with increased risk of developing heart disease or premature death in the Danish MONICA project [1]. This could be related to too little muscle mass in the region. Waist circumference and hip circumference have opposite relationships with metabolic health.

A body shape index (ABSI) is a related measure which incorporates waist circumference, height and BMI [2]. It is calculated as Waist circumference/(BMI^2/3×height^1/2). Death rates have been shown to increase almost exponentially with above average baseline ABSI.

A cross-sectional study of 9206 adults aged 20-69 years from Australia showed that waist-hip ratio is a better predictor of cardiovascular disease and coronary artery disease mortality than waist circumference [3]. Waist circumference was in turn a better predictor than BMI. Waist-hip ratio was the dominant, independent predictive variable for cardiovascular disease and coronary artery disease deaths in Australian men and women.

Another Australian study of 8662 adults with 15 year mortality follow-up found that obesity measures waist circumference and waist-hip ratio were significant univariate predictors while BMI was not [4]. In multivariable analysis, waist-hip ratio was identified as a key independent risk factor for coronary artery disease and cardiovascular disease deaths. They also found that the preferred model for predicting coronary artery disease and cardiovascular death was a combination of central obesity and smoking. In their study there was no added influence for measured lipids or blood pressure, though they were significant univariate predictors of coronary and cardiovascular deaths. Waist-to-stature ratio is another measure of central obesity which is a highly significant, but less powerful predictor of cardiovascular mortality. But it was not found to be more useful than waist circumference alone in another report from the same authors [5]. They concluded that waist-hip ratio is the preferred clinical measure of obesity for predicting all cause and cardiovascular disease mortality.

A recent large cohort study evaluated European and Australian adults from 11 countries and included 90 487 men and women, between 30 to 74 years, having no cardiovascular disease on recruitment from 1986 to 2010 [6]. Maximal follow-up in the study was 24 years. There was a J- or U-shaped association between all-cause death and most obesity measures. For all hip sizes, having a smaller waist was strongly associated with lower risk of death except for men with the smallest hips. Among those with smaller waists, hip size was strongly negatively associated with risk of death. Authors concluded that there is a complex relationship between hip circumference, waist circumference and risk of death. Particularly for individuals with smaller waists, having larger hips was protective. Simultaneous consideration of both waist and hip circumference identified almost 20% more people as being at higher risk of death.

References

1. Heitmann BL, Frederiksen P. Thigh circumference and risk of heart disease and premature death: prospective cohort study. BMJ. 2009 Sep 3;339:b3292. doi: 10.1136/bmj.b3292. PMID: 19729416; PMCID: PMC2737606.
2. Krakauer NY, Krakauer JC. A new body shape index predicts mortality hazard independently of body mass index. PLoS One. 2012;7(7):e39504. doi: 10.1371/journal.pone.0039504. Epub 2012 Jul 18. PMID: 22815707; PMCID: PMC3399847.
3. Welborn TA, Dhaliwal SS, Bennett SA. Waist-hip ratio is the dominant risk factor predicting cardiovascular death in Australia. Med J Aust. 2003 Dec 1-15;179(11-12):580-5. doi: 10.5694/j.1326-5377.2003.tb05704.x. PMID: 14636121.
4. Dhaliwal SS, Welborn TA. Central obesity and cigarette smoking are key determinants of cardiovascular disease deaths in Australia: a public health perspective. Prev Med. 2009 Aug-Sep;49(2-3):153-7. doi: 10.1016/j.ypmed.2009.07.019. Epub 2009 Aug 4. PMID: 19660494.
5. Welborn TA, Dhaliwal SS. Preferred clinical measures of central obesity for predicting mortality. Eur J Clin Nutr. 2007 Dec;61(12):1373-9. doi: 10.1038/sj.ejcn.1602656. Epub 2007 Feb 14. PMID: 17299478.
6. Cameron AJ, Romaniuk H, Orellana L, Dallongeville J, Dobson AJ, Drygas W, Ferrario M, Ferrieres J, Giampaoli S, Gianfagna F, Iacoviello L, Jousilahti P, Kee F, Moitry M, Niiranen TJ, Pająk A, Palmieri L, Palosaari T, Satu M, Tamosiunas A, Thorand B, Toft U, Vanuzzo D, Veikko S, Veronesi G, Wilsgaard T, Kuulasmaa K, Söderberg S. Combined Influence of Waist and Hip Circumference on Risk of Death in a Large Cohort of European and Australian Adults. J Am Heart Assoc. 2020 Jul 7;9(13):e015189. doi: 10.1161/JAHA.119.015189. Epub 2020 Jun 30. PMID: 32602397; PMCID: PMC7670538.