Half of Chinese Adults Have Prediabetes or Diabetes

Kristin Jenkins

June 27, 2017

The size of the diabetes epidemic in China appears to be smaller than previously reported but is still fast approaching rates seen in the United States, a survey now shows.

The estimated overall prevalence of prediabetes in the 2013 China Chronic Disease and Risk Factors Surveillance study — a nationwide cross-sectional analysis conducted every 3 years — was 35.7% compared with 50.1% in the 2010 survey (N Engl J Med. 2010; 362:1090-1101), says a research team led by Linhong Wang, PhD, of the Chinese Center for Disease Control and Prevention in Beijing.

This new rate, which is almost as high as the 2011–2012 estimated rate of 36.5% for prediabetes in the US population, may be the result of using an alternate method of measuring HbA1c in the 2013 survey, say the investigators in their report, published in the June 27 issue of the Journal of the American Medical Association.

"With approximately 1.09 billion adults in total in mainland China, it is projected that 388.1 million Chinese adults (200.4 million men and 187.7 million women) may have had prediabetes in 2013, considerably reduced from the projected number of 493.4 million individuals in 2010," the study authors write.

The significantly lower diabetes prevalence rates in the country's largest minorities — including Tibetans and Muslim Chinese (4.3% and 10.6%, respectively) — compared with Han Chinese, the country's majority population (14.7%), may also have played a role, they suggest, since the 2013 survey was the first to include significant numbers of minorities.

"The large sample size of this study provided, to our knowledge, the first direct comparison of diabetes prevalence among major minority groups in China within one survey, using the latest diabetes diagnosis criteria," Dr Wang and colleagues say.

Chinese More Likely to Have Diabetes at Lower BMI

The 2013 estimated overall prevalence of diagnosed and undiagnosed diabetes was 10.9%, with a prevalence of 4.0% for diagnosed diabetes.

The investigators didn't differentiate between type 1 and type 2 diabetes.

Overall, 47% of Chinese adults 18 years of age and older were estimated to have either diabetes or prediabetes in 2013 — a number that is only slightly lower than in the United States, where it is estimated that between 49% to 52% of adults have diabetes or prediabetes.

Both the 2010 and 2013 Chinese surveys followed identical protocols and quality-control strategies but used different methods to calculate HbA1c levels, which have led to the disparate results, Dr Wang and colleagues indicate. In 2010, a formula taken from an internal validation study was used to measure capillary HbA1c, whereas in 2013, HbA1c was measured from venous blood samples stored at -80°C — "a more reliable method," they observe.

For the study, fasting plasma glucose and HbA1c levels were measured in 170,287 participants. Those without diagnosed diabetes underwent glucose tolerance testing. Diabetes and prediabetes were defined using 2010 American Diabetes Association criteria, and an HbA1c concentration of less than 7.0% among treated patients with diabetes was considered adequate glycemic control.

Participants' awareness of a diabetes diagnosis as well as treatment and outcomes were also evaluated. Some 36.5% participants with diabetes were aware of their diagnosis, 32.2% were treated, and 49.2% had adequate glycemic control, the study authors report.

Although this latest 2013 survey demonstrates that the prevalence of estimated diabetes (both diagnosed and undiagnosed) in China may not be as epidemic as the 2010 survey indicated, it is still only slightly lower than 2011–2012 estimates in the United States (10.9% vs 12%–15%).

This latest 2013 survey also indicates that respondents in China are much more likely to be diagnosed with diabetes at a lower body mass index (BMI) than their American counterparts (24.0 vs 28.7) and are more likely to be merely overweight when diagnosed compared with Americans (15.4% vs 8%–9%).

Asians have "a higher risk of developing diabetes at a given BMI," the study authors point out. After adjustment for Asian-specific BMI cutoffs, however, the number of Chinese participants who were overweight and had a diagnosis of diabetes was similar to their US counterparts.

And just because the problem isn't as bad as previously thought doesn't mean there isn't an urgent need for action.

In a recent review of diabetes surveys in China, as reported by in 2016, the authors note that the prevalence of prediabetes is "exponentially rising," and there are thought to be alarming numbers of people with undiagnosed diabetes.

"Implementation of effective steps to suppress the conversion from prediabetes to diabetes mellitus and the recognition and efficient treatment of those with diabetes are desperately needed in China," the authors concluded.

Tibetan and Muslim Chinese: Much Lower Rates of Diabetes Than Han

In their new JAMA paper, Dr Wang and colleagues note that China has 56 ethnic groups, and there are "substantial differences" genetically, culturally, socioeconomically, and in terms of the climate and geographic features of the areas in which residents live.

Of the minority ethnic groups, those with at least 1000 survey participants (Tibetan, Zhuang, Manchu, Uyghur, and Muslim) were compared with Han participants in the 2013 survey.

Tibetan and Muslim Chinese had significantly lower crude prevalence of diabetes than Han participants (< .001). Adjusted odds ratios compared with Han participants were 0.42 for diabetes and 0.77 for prediabetes in Tibetan Chinese and 0.73 for diabetes and 0.78 for prediabetes in Muslim Chinese.

More study is needed to investigate the impact of these cultural differences, the authors say.

For instance, two genes involved in oxygen processing were found in most Tibetan Chinese. Members of this ethnic minority group thrive in high altitudes and have low BMIs.

"According to the survey, Tibetans may have higher levels of physical activity, which is to be expected because of their nomadic way of life," Dr Wang and colleagues point out. However, Tibetans also consume more meat and fewer vegetables or fruits and tend to drink copious amounts of tea laced with salt and butter.

The study authors report no relevant financial relationships.

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JAMA. 2017;317:2515-2523. Article

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