VOL 49: OCTOBER • OCTOBRE 2003 Canadian Family Physician • Le Médecin de famille canadien 1287
clinical challenge clinical challenge
défi clinique défi clinique
F
or many years we have recognized that obesity is a risk factor for cardiovascular disease (CVD), as well as being associated with insulin resistance and development of type 2 diabetes.1All fat is not created equal, however. Intra-abdominal fat (visceral fat) is more “metabolically active” and, as such, is associated with metabolic syndrome.
Metabolic syndrome is characterized by hypertension, hyperglycemia, low high-density lipoprotein choles- terol, and nontraditional markers, such as insulin resistance, hyperinsulinemia, raised apolipoprotein B (apo-B), and small, dense low-density lipoprotein (LDL) cholesterol particles. The presence of these nontraditional markers predicts a 20-fold increase in risk of CVD, even when patients do not have hyperten- sion, diabetes, or elevated cholesterol levels.
Intra-abdominal fat can be assessed using com- puted tomography and magnetic resonance imaging, but most of us do not have ready access to these scans, especially for this purpose. Measurement of waist circumference and plasma triglyceride levels, however, can easily and accurately assess this risk factor. In fact, waist measurement predicts subse- quent coronary artery
disease better than body mass index does.2
Waist circumference is measured midway between the costal margin and the anterior superior iliac spine.
Sensitivity and specificity analyses conducted in a sample of men aged 30 to 65 years showed that a cut- off point of 90 cm in waist measurement is the best way to distinguish men with hyperinsulinemia and increased apo-B concen- trations from those with
normal levels.3 A fasting triglyceride concentration of 2 mmol/L provides the best cutoff point for identifying men with the small, dense, LDL phenotype.3
Using these simple cutoff values shows that more than 80% of men with a waist circumference >90 cm (36 inches) and fasting triglyceride concentrations
>2 mmol/L carry the atherogenic metabolic triad.4 Sex and ethnic origin make a difference in the relationship of waist measurement to accumulation of visceral adipose tissue, however, and there might be different cutoff values for different groups.
Nevertheless, monitoring waist circumference and plasma triglyceride levels could provide practitioners with another tool for assessing risk of CVD in white men. It might also be a marker patients can more readily comprehend. They would have “visible” proof of improvement in risk as their girth receded.
Acknowledgment
I thank Dr Bruce Josephson, a cardiologist in the Department of Medicine at Dalhousie University in Halifax, NS, for reviewing the draft copy of this article.
References
1. Chan JM, Rimm EB, Colditz GA, Stampfer MJ, Willett WC. Obesity, fat dis- tribution, and weight gain as risk factors for clinical diabetes in men. Diabetes Care 1994;17(9):961-9.
2. Lemieux I, Pascot A, Couillard C, Lamarche B, Tchernof A, Almeras N, et al. Hypertriglyceridemic waist: a marker of the atherogenic metabolic triad (hyperinsulinemia; hyperapolipoprotein B; small, dense LDL) in men? Circulation 2000;102(2):179-84.
3. Després J-P, Lemieux I, Prud’homme D. Treatment of obesity: need to focus on high risk abdominally obese patients.
BMJ 2001;322:716-20.
4. Ohlson LO, Larsson B, Svardsudd K, Welin L, Eriksson H, Wilhelmsen L, et al.
The infl uence of body fat distribution on the incidence of diabetes mellitus: 13.5 years of follow-up of the participants in the study of men born in 1913. Diabetes 1985;34:1055-8.
Just the Berries
Waist circumference and cardiovascular risk
John Hickey, MD
“Just the Berries” for Family Physicians originated at St Martha’s Regional Hospital in 1991 as a newsletter for members of the Department of Family Medicine. Its pur- pose was to provide useful, practical, and current informa- tion to busy family physicians. It is now distributed by the Medical Society of Nova Scotia to all family physicians in Nova Scotia. Topics discussed are suggested by family physicians and, in many cases, articles are researched and written by family physicians.
Just the Berries has been available on the Internet for sev- eral years. You can fi nd it at www.theberries.ns.ca. Visit the site and browse the Archives and the Berries of the Week.
We are always looking for articles on topics of interest to family physicians. If you are interested in contributing an article, contact us through the site. Articles should be short (350 to 1200 words), must be referenced, and must include levels of evidence and the resources searched for the data.
All articles will be peer reviewed before publication.
Dr Hickey is a member of the Department of Family Medicine at St Martha’s Regional Hospital in Antigonish, NS, and is editor of “Just the Berries” for Family Physicians.