"The metabolic syndrome has become increasingly common in this Asian population and the prevalence is about to catch up with that in Western populations. That's a very dangerous sign in terms of cardiovascular disease," said Frank B. Hu, M.D., Ph.D. from the Harvard School of Public Health in Boston, Massachusetts.
The researchers, including lead author Yao He, M.D., Ph.D. from Harvard and also the Chinese PLA General Hospital in Beijing, China, interviewed and examined 2,334 people age 60 years or older who lived in the Beijing metropolitan area. Almost a third to almost half of the participants had metabolic syndrome. Metabolic syndrome is a cluster of five risk factors: central obesity defined by waist circumference, high blood pressure, low HDL ("good" cholesterol), high triglycerides, and high blood sugar.
"There have been some reports from developing countries, including China, on the prevalence of metabolic syndrome, but this is actually the first study to look at the urban elderly population in a systematic way and to document not only the prevalence of metabolic syndrome, but also its relationship with cardiovascular disease," Dr. Hu said.
According to the definition of metabolic disease from the U.S. National Cholesterol Education Program (NCEP), just over 30 percent of the participants had metabolic syndrome. However, 46 percent of the people in this study met the criteria for metabolic syndrome used by the International Diabetes Federation (IDF). The presence of metabolic syndrome was also associated with higher prevalence of cardiovascular disease.
"Using the IDF definition, the prevalence of metabolic syndrome increased substantially, because a lower cut-off point for central obesity was used. And what's interesting is that in this study it appears that metabolic syndrome as defined by the IDF is more strongly correlated with cardiovascular disease, including heart disease, stroke and peripheral artery disease, than the metabolic syndrome defined by the U.S. National Cholesterol Education Program criteria," Dr. Hu said. "This is not surprising given that Chinese people develop diabetes and cardiovascular disease at much lower BMI (Body Mass Index) compared to Caucasians."
Dr. Hu said the findings indicate that as the economy and lifestyles in China become more westernized, people in China are also developing "western" patterns of cardiovascular disease risk.
"So the population is undergoing the transition from under-nutrition to over-nutrition and from underweight to obesity. In the next several decades, I think the obesity problem will get worse and the prevalence of metabolic syndrome and also its consequences, such as diabetes and cardiovascular disease, will continue to increase. This will create a huge burden for the health care system," Dr. Hu said.
Dr. Hu pointed out that this study just took a snapshot of the health of a selected urban population. He said future studies should follow people in China over time to track metabolic syndrome and how well it predicts the development of diabetes and cardiovascular disease.
In the meantime, he urged clinicians to look beyond the diagnosis and treatment of individual risk factors, such as high blood pressure, and instead pay closer attention to preventing and treating the cluster of risk factors that make up the metabolic syndrome.
Zhengming Chen, M.D., Ph.D. from the University of Oxford in Oxford, United Kingdom, who was not connected with this study, said the results show that metabolic syndrome is more prevalent in Chinese cities than most people have realized.
"Chronic non-communicable disease is increasingly becoming prevalent in China, especially in cities such as Beijing, due to changing of dietary patterns and lifestyle," he said. "The future burden from cardiovascular disease or other chronic disease in China will be substantial."
Dr. Chen pointed out that this study is just a first step toward understanding metabolic syndrome and cardiovascular disease in China.
"This study is relatively small and, as discussed in the paper, it is only a cross-sectional study. A large prospective study in China is needed to assess the relationship between metabolic syndrome and risk of cardiovascular disease mortality and incidence," he said.
This study was supported by research grants from the Main State Basic Research Development Program of China and the Health Service in the Health Ministry of China. Dr. Hu is partly supported by the American Heart Association Established Investigator Award.