Diabetes in China, already a greater burden than in any other country, is probably being exacerbated by its one-child policy.
About 100 million families have just one child, the Chinese government says. That translates into an equal number of firstborns, a status that researchers are finding may be tied to conditions that raise obesity risk, said Chong Yap Seng, a scientist at Singapore’s National University Hospital.
Chong and colleagues in Beijing and Southampton, England, are studying the biological mechanisms that have conspired with diet and lifestyle changes to produce 92.3 million diabetics in China, almost four times as many as in the U.S. While firstborns start out smaller than siblings, they gain weight faster and are bigger as adults, a trajectory that increases obesity risk and may explain why China’s diabetes prevalence has more than tripled in a decade, said Chong.
“You have a whole group of firstborns growing up in China who are all at a slightly higher risk for obesity and diabetes than in other societies,” said Chong, an obstetrician who is investigating the origins of diabetes on the island-nation of Singapore, where 74 percent of residents are ethnically Chinese.
Their findings will help shape new approaches to preventing diabetes and other chronic diseases that Health Minister Chen Zhu says threaten to sap the labor force and slow the pace of economic growth.
For drugmakers such as Novo Nordisk A/S (NOVOB) and Eli Lilly & Co. (LLY), the metabolic condition is a boon for revenue. Sales of diabetes medicines in China will expand 20 percent a year to reach $3.2 billion by 2016, consulting firm IMS Health Inc. says.
The one-child policy was introduced in 1979 to curb a population growing 1.4 percent a year and to promote prosperity. Some exceptions to the policy are allowed, such as permitting rural families to have a second child if the first is a girl. Those who can afford to can have a second or third baby by paying a fine.
Rising numbers of diabetics, though, are costing China’s economy $26 billion annually in medical care and lost productivity, according to the International Diabetes Federation. The prevalence of diabetes in China, a nation of 1.34 billion people, is 8.8 percent. The U.S. has a diabetes prevalence of 9.3 percent and 24.1 million sufferers, according to federation estimates released last month.
Within 18 years, China is projected to have 130 million sufferers of Type 2 diabetes, the form of the disease in which the body stops responding properly to the hormone insulin, according to the Brussels-based federation. The disease is already killing 1.2 million Chinese a year because of kidney failure, heart attack and other associated conditions, it said in a Nov. 14 report.
Diabetes occurs earlier and with worse complications in Asians than Caucasians, diabetes researchers say. One reason is that Asians have a greater tendency to carry excess weight around their abdomens, where it’s more likely to cause insulin- resistance and high cholesterol, Canadian researchers found in a study published last year. Their study suggested that ethnic Chinese with a body mass index of 25 have the equivalent risk of diabetes as a white person with a BMI of 30.
The proportion of overweight adults in China was one in four in 2008, from one in six in 2002, according to the World Health Organization. It estimates that almost a third of men and women don’t do enough physical activity. Obesity is becoming a bigger danger for the young as well, with the rate among children younger than 7 years almost tripling to 3.4 percent in 2006 from 20 years earlier, according to an Oct. 12 study published in the journal PLOS One.
While increasing car ownership and more sedentary lifestyles, combined with greater availability of energy-dense food, is pushing calorie consumption to excess, the origins of obesity may begin before birth, according to Mark Hanson, professor of medicine at the University of Southampton, who studies the developmental roots of health and disease.
A baby that is the result of a woman’s first full-term pregnancy is typically 200 grams (half a pound) lighter at birth than non-firstborn babies, according to Chong. Firstborns catch up later in life and are typically heavier as adults, according to a 2010 U.K. study in the Journal of Clinical Endocrinology and Metabolism, which followed 276 unborn babies through to adulthood. Their smaller size at birth is probably a result of maternal constraint of intra-uterine growth, they said.
A 2010 study by researchers in Brazil, the U.K. and Italy published in PLOS One found that birth order is associated with increased body mass, higher levels of fat and metabolic risk in young adult men in Brazil. The study assessed 2,249 men ages 17 to 19 and their medical records from birth. Researchers measured metabolic risk by blood pressure, cholesterol levels, blood fats and fat mass.
The weight-gain trajectory may be influenced by a mechanism known as fetal programming in which the fetus picks up environmental cues, such as nutrient status, inside the uterus and tweaks its development to suit what it predicts will give it the best chance of survival in later life, Hanson said.
“If that forecast turns out to be wrong, then the baby’s biology is mismatched to the world in which he or she will live,” said Hanson, who wrote about the concept with Peter Gluckman, New Zealand’s chief science adviser, in the 2007 book Mismatch: Why Our World No Longer Fits Our Bodies.
Early postnatal growth rates are strongly influenced by a drive to compensate for restraint or enhancement of fetal growth by maternal-uterine factors, Cambridge University researchers reported in a study in 2002. The mechanisms that signal growth trajectories are unknown, but may involve programming of appetite, they said.
A woman’s first pregnancy primes placental blood supply for subsequent pregnancies, improving the availability of nutrients to the fetus, researchers at the Women’s and Children’s Hospital in Adelaide, South Australia, found in a study published in 2003.
Babies born during periods of famine are especially vulnerable to obesity-linked diseases as adults, Hanson said. For example, Chinese who experienced hunger as infants during the Great Leap Forward, an economic policy between 1958 and 1961 that caused tens of millions of people to starve to death, had a higher risk of developing diabetes and heart disease as adults, Harvard University researchers found in a study published in 2011. The risk was exacerbated by calorie-dense Western foods, they found.
The findings underscore the public-health importance of ensuring young women and girls have adequate nutrition, said Robert Beaglehole, an emeritus professor with the University of Auckland’s school of population health.
“Interventions to improve nutrition before and during pregnancies and after delivery are crucial as they will have a big impact in 20-30 years,” said Beaglehole, a former director of chronic disease and health promotion at the World Health Organization, who first visited China as a student in the 1960s.
Strategies addressing diabetes in China typically focus on adults already suffering the disease and its complications rather than prevention through supporting the nutrition of pregnant women and babies, said Yang Huixia, director of obstetrics and gynecology at the Peking University First Hospital.
BGI, a Shenzhen-based genetic sequencing institute, is looking elsewhere to understand the causes of diabetes in China. In research supported by the Novo Nordisk Foundation Center for Basic Metabolic Research in Copenhagen, stool samples from 345 Chinese with diabetes were analyzed. Those with the disease were found to have a distinct collection of microbes present in their bowel, according to a study published in Nature in September.
“If we use the biomarkers to identify those high-risk people, monitor their health and take intervention measures in the early stages, the disease could be prevented or delayed,” said Li Qibin, manager of BGI’s Sino-Danish Diabetes Project.
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