Study of Oakland parents finds smoking increases diabetes risk for daughters

A new study of families in and near Oakland reports that tobacco-smoking parents increase their daughter’s risk of developing diabetes mellitus, also known as type 2 diabetes. Daughters exposed to second-hand smoke while in the womb are predisposed to developing the disease later as adults.

Study reports were published in the February 9 issue of the Journal of Developmental Origins of Health and Disease, the result of a collaborative study between The Public Health Institute (PHI) and the University of California, Davis. The longitudinal study analyzed a sample of 1,801 women for more than fifty years.

According to the study, “The impact of prenatal parental tobacco smoking on the risk of diabetes mellitus in middle-aged women” found that women whose mothers smoked while being pregnant were two to three times as likely to be diabetic by middle age, in contrast to other women whose mothers did not smoke during their pregnancy.

The American Diabetes Association states on their website that individuals who suffer from type 2 diabetes don’t properly produce insulin, a hormone that helps the human body use glucose for energy. The lack of the hormone causes the pancreas to produce extra insulin in order to catch up. But in the long run, the pancreas can’t keep up with insulin production in order to keep blood glucose levels normal.

According to Barbara Cohn, article co-author and director of PHI’s Child Health and Development Studies, the late Jacob Yerushalmy initiated the study. Yerushalmy is known for founding the Department of Biostatistics at the University of California, Berkeley. He recruited pregnant women for the study from the years 1959 to 1967 with the assistance of the Kaiser Permanente Foundation Health Plan in the San Francisco Bay Area.

Pregnant women who were seeking obstetric care at Kaiser Permanente in the late 1950’s and throughout the 1960’s were asked if they were willing to participate in the study. If they accepted, follow-up studies continued with their daughters at the ages of 5, 9,10, then again in adolescence, and then in a recent follow-up study that ran from 2010 to 2013. “It made it really easy to enroll the women because it was a collaboration with Kaiser,” said Cohn.

The mothers resided in and near the city of Oakland and were asked whether they or their partner or spouse smoked tobacco during a pregnancy interview. Only mothers who reported that they smoke at least one cigarette a day were considered for the study. Fathers who smoke at least one cigar or pipe a day were considered for the study as well.

The researchers then analyzed results from four separate categories: When only mothers smoked, when only fathers smoked, when both mothers and fathers smoked and when neither mothers nor fathers smoked.

According to Cohn, most the study’s participants continued to live in California since the state was prospering throughout the study’s fifty-year period, making it easier for researchers to follow up with participants. Researchers communicated with the daughters of the tobacco-smoking mothers at a young age, letting them know that their mothers and themselves were part of a longitudinal study. After informing them, researchers asked the daughters if they wanted to continue to participate in the study as adults. Girls were specifically targeted for the study because their data was used breast cancer research as well.

While the women were specifically targeted for breast cancer research, but the study’s lead author, UC Davis assistant professor of environmental toxicology Dr. Michele La Merrill, was interested in researching diabetes and tested participant’s blood samples.

One key takeaway of this new study is that the birth weight of the tobacco-smoking parents’ daughters was not linked to the development of diabetes. Previous studies by other researchers had only found that prenatal tobacco exposure to be linked to a child’s low birth weight and higher rates of obesity. But researchers from this new study found that “smoking of parents is by itself a risk factor for diabetes, independent of obesity or birth weight,” said La Merrill. “If a parent smokes, you’re not protected from diabetes just because you’re lean.”

In addition, this new study found that the mother’s smoking behavior was a stronger predictor for the development of diabetes for their daughters than the father’s smoking behavior. Researchers know that the fetus is more exposed through the mother’s smoking behavior, because the mother is directly passing on the chemicals found in second-hand smoke to her baby when smoking. In a press release, the PHI researchers stated, “Fathers who smoked while their daughters were in utero contributed to an increased diabetes risk for their children, but more research is needed to establish the extent of that risk.” Nonetheless, the father’s smoking behavior still plays a role, since he is exposing the mother to the chemicals in second-hand smoke, which can then be transmitted to the child.

“We care because many people would like to be thinking about prevention, because diabetes does a lot of damage,” said Cohn. According to Cohn, having diabetes can lead to complications like kidney failure, eye damage and heart problems.

According to the American Diabetes Association, type 2 diabetes is the most common form of the disease is and mostly found among the African American, Latino, Native American, and Asian Pacific Islander and older populations.

At the moment, type 2 diabetes is treated with lifestyle changes such as healthier eating habits and becoming more active, taking oral medications, and insulin intake through injection or a pump. Cohn hopes that if they can identify the gene that makes some people predisposed to diabetes, then maybe they can fix it – but for now more research will have to be done. “It’s a very serious health problem and it is on the rise,” said Cohn.

Photo source: “CIGARETTE” by Fried Dough on Flickr, shared via Creative Commons