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NEW YORK, March 20 (UPI) -- Exposure to tobacco smoke in the womb or picking up the cigarette habit in childhood or adolescence greatly increases the risk of developing type 2 diabetes in adulthood, a new study finds. The preliminary research, which included more than 400,000 adults in the UK Biobank, was presented Wednesday at the American Heart Association's Epidemiology and Prevention│Lifestyle and Cardiometabolic Scientific Sessions 2024 in Chicago.
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Participants who had a genetic predisposition to type 2 diabetes and started smoking in childhood or adolescence had the highest risk of developing the illness.
Tobacco exposure in adulthood is a well-established risk factor for type 2 diabetes. Previous research has uncovered that cigarette smokers are 30% to 40% more likely to develop type 2 diabetes than nonsmokers.
"The findings emphasize the importance of preventing tobacco exposures in early life stages, including during pregnancy, especially for people with high genetic risk for type 2 diabetes," senior author Victor Wenze Zhong, a professor and department chair of epidemiology and biostatistics at Shanghai Jiao Tong University School of Medicine in China, told UPI via email.
"Earlier smoking initiation is associated with a higher risk of type 2 diabetes compared with never smoking. Adopting a healthy lifestyle later in adulthood could lower risk of type 2 diabetes among people who have tobacco exposure in utero, childhood or adolescence," said Zhong, who earned a doctorate in nutritional epidemiology from the University of North Carolina-Chapel Hill.
In this study, researchers examined data for 433,874 adults in the UK Biobank -- a large biomedical database and research resource with health records of about 500,000 adults enrolled from 2006 to 2010. These adults live in the United Kingdom and obtained health care through the country's National Health Service.
The researchers estimated the associations of tobacco exposure before birth and initiation of smoking during childhood (ages 5 to 14) or adolescence (ages 15 to 17) with the development of type 2 diabetes.
They also explored whether following a healthy lifestyle as an adult, such as eating a nutritious diet, exercising, getting sufficient sleep, maintaining normal weight and not smoking may have affected high-risk individuals' development of type 2 diabetes.
The analysis found that tobacco exposure before birth was associated with a 20% increased risk of type 2 diabetes compared to individuals who never smoked.
People who began smoking in childhood had a 118% risk of type 2 diabetes; those who started smoking as adolescents had a 57% higher risk; and those who started smoking as adults had a 34% greater risk compared to those who never smoked.
Compared with people who had no early-life tobacco exposure and a low genetic predisposition for type 2 diabetes, participants with a high genetic risk score had a 302% higher risk of developing type 2 diabetes if they were also exposed to tobacco before birth, a 593% higher risk if they began smoking in childhood and a 404% higher risk if they took up the habit in adolescence.
The elevated risk of type 2 diabetes stemming from early-life tobacco exposures and high genetic risk was reduced by 67% to 81% among individuals who adhered to a healthy lifestyle in later life compared to those who did not.
"It's important to investigate whether and what factors in later life could modify the type 2 diabetes risk associated with early-life factors," Zhong said. "Addressing these gaps may provide novel insights into early prevention of type 2 diabetes."
The authors acknowledged that this is an observational study, meaning the findings indicate an association, but don't confirm direct cause and effect. In addition, they pointed out that that the participants self-reported information about tobacco exposure, so the data may include possible errors in memory.
"Like other observational studies, this one needs to be validated in other populations," Dr. Robert Eckel, a past president of the American Heart Association, told UPI via email. He was not involved in the study.
The investigation into "the relationship between tobacco exposure and type 2 diabetes incidence is novel," said Eckel, a professor emeritus of medicine in the division of endocrinology, metabolism and diabetes and the division of cardiology at the University of Colorado Anschutz Medical Campus in Aurora, Colo.
He added that "type 2 diabetes is not due to one or two genes but numerous genes that all contribute additively to risk." When exposed to tobacco as described, these genes magnify the risk of developing type 2 diabetes three to six times, he noted.
"While we have known for over a decade that combustible tobacco use is a cause of type 2 diabetes, the strength of the association to in-utero and childhood exposure to combustible tobacco is still shocking," Dr. Adam Goldstein, a professor of family medicine and director of tobacco intervention programs at the University of North Carolina-Chapel Hill's School of Medicine, told UPI via email.
"This new study should force physicians and policymakers to redouble their efforts to not only eliminate combustible tobacco use among adults, but we must immediately eliminate all secondhand smoke exposure to pregnant women and children," Goldstein said.
Since the collection of data for this study, vaping devices have proliferated around the world and may be a novel risk factor for the development of type 2 diabetes, Dr. Denitza Blagev, a pulmonary and critical care physician and senior medical director for community hospitals at Intermountain Health in Salt Lake City, told UPI via email.
"I would not recommend thinking of vaping/e-cigarette use or switching to e-cigs as a way of reducing the risks of smoking described in this study," Blagev said.
While "genetic susceptibility isn't under one's control," the study emphasizes that people can take steps to alter their risk, Elizabeth Jensen, an associate professor of epidemiology and prevention at Wake Forest University School of Medicine in Winston-Salem, N.C., told UPI via email.
For instance, Jensen said, "Individuals with a family history of type 2 diabetes may be able to modify future risk to their offspring by avoiding smoking during pregnancy."
