Cigarette smoking has been identified as a risk factor for the onset of diabetes. The findings of a recent study indicate that even prenatal exposure to tobacco can also be an influencing factor for Type 2 diabetes.

After evaluating almost half a million adults from the UK Biobank, researchers determined that being exposed to tobacco before birth, as well as starting smoking during childhood or adolescence, significantly increases the risk of developing Type 2 diabetes later in life.

Earlier research found that smokers are 30%–40% at higher risk of developing Type 2 diabetes when compared to those who do not smoke.

"However, how early-life tobacco exposure may impact the development of Type 2 diabetes, as well as whether this association varies by different genetic predisposition to Type 2 diabetes are unclear," Victor Wenze Zhong, senior study author of the latest study, said in a news release.

The researchers used data from 476,000 adults to evaluate the connections between tobacco exposure before birth and starting smoking during childhood (ages 5-14) or adolescence (ages 15-17) to the onset of Type 2 diabetes. By employing a polygenic risk score (a risk assessment based on genetics) researchers estimated the potential interaction and combined impacts of early-life tobacco exposure and genetic vulnerability on the risk of developing Type 2 diabetes.

They also studied if a healthy lifestyle as an adult may affect the development of Type 2 diabetes among high-risk individuals. This includes a healthy diet, exercise, sufficient sleep, normal weight, and not smoking.

These are the important findings:

1) Early-life tobacco exposure, which includes exposure before birth or starting to smoke during childhood or adolescence, is closely linked to the development of Type 2 diabetes. This association is particularly significant for individuals with a genetic predisposition to the disease.

2) Prenatal exposure to tobacco is associated with a 22% higher risk of Type 2 diabetes compared to non-smokers.

3) The risk of diabetes increases significantly based on the age at which people start smoking: individuals who start the habit in childhood have double the risk, while those who start during adolescence have a 57% higher risk. Those who start smoking as an adult carry a 33% higher risk than people who never smoked.

4) In people with early-life tobacco exposure and a high genetic risk score, the risk of diabetes is even higher. When compared to non-smokers with low genetic risk, they have 330% higher risk if the exposure is before birth, 639% higher risk if they started smoking in childhood, and 427% higher risk if they started in adolescence.

However, with a healthy lifestyle later in life, these risks can be significantly reduced by 67% to 81% compared to individuals who do not follow a healthy lifestyle.

The researchers believe that their study brings hope for high-risk individuals, as making lifestyle changes could notably decrease their risk of developing diabetes.

"Although early-life tobacco exposure and genetic predisposition are not things children can control, our results provide evidence that lifestyle factors may powerfully modify the risk of Type 2 diabetes. It's important for individuals, particularly those exposed to tobacco early in life and with a high genetic risk of Type 2 diabetes, to adhere to a healthy lifestyle to reduce their risk of developing Type 2 diabetes as adults," Zhong said.

Zhong, however, cautioned that the study found only an association between early-life tobacco exposure and Type 2 diabetes, not a causative relationship between the two.

The results of the study will be presented at the American Heart Association's Epidemiology and Prevention│Lifestyle and Cardiometabolic Scientific Sessions 2024, in Chicago.