Abstract & Commentary
Synopsis: The metabolic syndrome affects more than 1 in 5 Americans and is increased substantially in Mexican Americans and by several modifiable lifestyle factors.
Source: Park YW, et al. Arch Intern Med. 2003;163:427-436.
This report emanates from the third National Health and Nutrition Examination Survey (NHANES III), a face-to-face survey of individuals selected to represent the entire US population. Data collected included educational level, economic status, smoking status, alcohol consumption, physical activity, carbohydrate intake, and menopausal status.
In addition to questionnaire data, standardized medical examinations that included blood pressure, plasma lipid and blood glucose levels, and waist circumference took place at mobile medical centers. After exclusion of those who consumed anything besides water 6 hours prior to venipuncture, those who had missing data, and pregnant women, a total of 12,861 individuals were sampled in 89 locations between 1988 and 1994.
The definition of the metabolic syndrome used in this report comes from the Third Report of the National Cholesterol Education Program Adult Treatment Panel (ATP III)1 and includes 3 or more of the following:
- abdominal obesity (waist circumference > 102 cm in men, > 88 cm in women);
- high triglyceride level (> 150 mg/dL);
- low HDL cholesterol level (< 40 mg/dL for men, < 50 mg/dL for women);
- high blood pressure (systolic > 130 mm Hg or diastolic > 85 mm Hg) or taking antihypertensives; and
- high fasting glucose (> 110 mg/dL) or taking hypoglycemics.
Prevalence rates of the metabolic syndrome were calculated, and multiple logistical regression analysis was used to estimate odds ratios (ORs) by age, ethnicity, and other variables collected.
The overall prevalence of the metabolic syndrome was 22.8% for men and 22.6% for women. Among men, the overall prevalence rates were 13.9%, 20.8%, and 24.3% for blacks, hispanics, and whites; all differences were significant except that between hispanic and white men (P = 0.06). Among women, the prevalence of metabolic syndrome was 20.9%, 22.9%, and 27% for black, white, and Mexican Americans. The prevalence was statistically significantly higher among Mexican American women. The prevalence of metabolic syndrome rose steeply for both genders older than 30, but appeared to peak between 50 and 70 years in men and between 60 and 80 years in women.
Body mass index was the strongest correlate of the risk of metabolic syndrome, but current cigarette smoking also greatly increased the risk. There were some gender differences between lifestyle factors and the ORs of metabolic syndrome. For men, high carbohydrate intake and low physical activity increased the odds. For women, previous smoking, nondrinking, low household income, and postmenopausal state increased the odds of metabolic syndrome.
Comment by Barbara A. Phillips, MD, MSPH
One in 5 of us had the metabolic syndrome almost 10 years ago (data collection for this study ended in 1994). Our trajectory toward national obesity has accelerated since that time, and I would guess that the rate of the metabolic syndrome is now 1 in 4. While we have been focusing on high technology and new pharmacologic agents, suicide by lifestyle has continued unabated.
There are a variety of definitions of the metabolic syndrome, but all include some measure of obesity, hypertension, hyperlipidemia, and insulin resistance. The criteria outlined above and promulgated by the ATP III Expert Panel are likely to be the ones we live with for awhile. The applicability of these criteria to different age, gender, and ethnic groups is a little suspect, though, since blacks had the lowest prevalence of the metabolic syndrome, but are more insulin resistant than are whites for any degree of obesity2 and have the highest overall coronary heart disease mortality of any US ethnic group.3
About once a week, one of my patients asks me about the Atkins diet. I suggest you check out what’s out there at http://atkinscenter.com. I no longer passionately discourage my patients (many of whom are morbidly obese, since I practice sleep medicine in Kentucky) from attempting this diet. The infamous Atkins diet, which focuses on reducing carbohydrates and increasing fat and protein, has some things going for it. At a time when many of our patients are "rediscovering" the Atkins diet, it is worth mentioning that the current study demonstrates that high carbohydrate intake is a risk factor for metabolic syndrome in men. In fact, there is plenty of evidence that increased carbohydrate intake may predispose to lipid abnormalities, insulin resistance, pancreatic cancer, and reduced bone density.4-11 I have lost my confidence in the low-fat diet, and do not think that it is a coincidence that the prevalence of obesity and the metabolic syndrome have skyrocketed while we were urging our patients to avoid fat and eat carbohydrates.
And, once again, as always: Exercise is good for you!! (and your patients).
Dr. Phillips is Professor of Medicine at the University of Kentucky and Director of Sleep Disorders Center, Samaritan Hospital, Lexington, KY.
1. Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults. Executive Summary of the Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA. 2001;285:2486-2496.
2. Karter AJ, et al. Diabetes. 1996;45:1547-1555.
3. Gillum RF. Cardiovascular disease in the United States: An epidemiologic overview In: Saunders E, ed. Cardiovascular Disease in Blacks. Philadelphia, PA: FA Davis Co Publishers; 1991: 3-16.
4. Liu S, et al. Am J Clin Nutr. 2001;73:560-566.
5. Sinha R, et al. N Engl J Med. 2002;346:802-810.
6. Han TS, et al. Obesity Research. 2002:923-931.
7. Layman DK, et al. The Journal of Nutrition. 133(2):405-410.
8. Layman DK, et al. The Journal of Nutrition. 2003; 133(2):411-417.
9. Promislow JH, et al. American Journal of Epidemiology. 2002;155(7):636-644.
10. Michaud DS, et al. Journal of the National Cancer Institute. 2002;94(17):1293-1300.