Boston, MA -- People who are a low weight at birth and have unhealthy habits as adults, such as eating nutritionally poor diets or smoking, may have a greater risk of developing type 2 diabetes than people born at an average weight who live similar lifestyles, according to a new study led by researchers from Harvard T.H. Chan School of Public Health. In the first study to comprehensively assess how early development interacts with adult behavior to influence type 2 diabetes risk, the researchers found that 18% of cases were attributable to the combined effect of low birth weight and unhealthy adult lifestyles.
"Most cases of type 2 diabetes could be prevented by the adoption of a healthier lifestyle, but these findings suggest that efforts focused on early life development, such as improving nutrition for pregnant women, could prevent additional cases," said Lu Qi, associate professor in the Department of Nutrition at Harvard Chan School and Channing Division of Network Medicine, Brigham and Women's Hospital, and the study's senior author.
The study appears online July 21, 2015 in BMJ.
Diabetes has become a worldwide epidemic, with 4.9 million attributable deaths in 2014 and an estimated 387 million people living with the disease, according to the International Diabetes Federation. Type 2 diabetes, which represents 85-95% of all cases, has been linked to both unhealthy lifestyles and negative early life development factors, including low birth weight (defined as less than 5.5 pounds for this study) and prenatal exposure to malnutrition.
While previous studies have looked at how adult lifestyles may modify early life risks, few have analyzed the joint effects of early life and unhealthy lifestyle factors on type 2 diabetes risk.
Qi and colleagues studied health data collected from 149,794 healthy men and women tracked by three large ongoing trials (Health Professionals Follow-up Study, Nurses' Health Study, and Nurses' Health Study II) for 20-30 years. Participants were scored on five lifestyle factors: diet, smoking, physical activity, alcohol consumption, and body mass index. Those who did not provide their birth weight were excluded from this analysis.
The researchers documented 11,709 new cases of type 2 diabetes during the study period. They found that 22% of these cases could be attributed to a lower birth weight alone, 59% to unhealthy lifestyle alone, and 18% to the interaction between both factors.
The researchers suggest that if a pregnant woman is poorly nourished it may cause the fetus to prepare for survival in a resource-scarce environment. When the adaptive response to prenatal starvation is mismatched with exposure to an affluent environment later in life, it can increase the risk of type 2 diabetes in adulthood.
"Our findings suggest that the public health consequences of unhealthy lifestyles would be larger in low birth weight populations," said Yanping Li, lead author and research scientist in the Department of Nutrition. "This is of critical importance in the developing countries undergoing rapid epidemiologic transition from traditional to Western lifestyles, such as China and India, where the prevalence of the Western dietary pattern, cigarette smoking, sedentary activities, obesity, and diabetes has been increasing dramatically, and low birth weight is still highly prevalent (around 17% in developing countries)."
Other Harvard Chan School authors of the study included Sylvia Ley, Deirdre Tobias, Stephanie Chiuve, Tyler VanderWeele, Janet Rich-Edwards, Gary Curhan, Walter Willett, JoAnn Manson, and Frank Hu.
The study cohorts were supported by grants P01 CA87969, UM1 CA176726, and UM1 CA167552 from the National Institutes of Health. This study was supported by the National Heart, Lung, and Blood Institute (HL071981, HL034594, HL126024), the National Institute of Diabetes and Digestive and Kidney Diseases (DK58845, DK091718, DK100383), the Boston Obesity Nutrition Research Center (DK46200), and United States-Israel Binational Science Foundation Grant 2011036. LQ was a recipient of the American Heart Association Scientist Development Award (0730094N).
"Birth weight and later life adherence to unhealthy lifestyles in predicting type 2 diabetes: prospective cohort study," Yanping Li, Sylvia H. Ley, Deirdre K. Tobias, Stephanie E. Chiuve, Tyler J. VanderWeele, Janet W. Rich-Edwards, Gary C. Curhan, Walter C. Willett, JoAnn E. Manson, Frank B. Hu, Lu Qi, BMJ, online July 21, 2015, doi: 10.1136/bmj.h3672
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Harvard T.H. Chan School of Public Health brings together dedicated experts from many disciplines to educate new generations of global health leaders and produce powerful ideas that improve the lives and health of people everywhere. As a community of leading scientists, educators, and students, we work together to take innovative ideas from the laboratory to people's lives--not only making scientific breakthroughs, but also working to change individual behaviors, public policies, and health care practices. Each year, more than 400 faculty members at Harvard Chan teach 1,000-plus full-time students from around the world and train thousands more through online and executive education courses. Founded in 1913 as the Harvard-MIT School of Health Officers, the School is recognized as America's oldest professional training program in public health.