TUESDAY, Jan. 10 (HealthDay News) -- Diabetes is a costly disease, and new research suggests those costs may extend far beyond the obvious expense of medicine and related health care.

The study authors found that young people with diabetes were more likely to drop out of high school and, over a lifetime, could expect to earn about $160,000 less than those without diabetes.

"A lot of studies, when they look at the toll diabetes takes, look at medical expenses when people are much older. We wanted to look at people who were much younger, and to look at non-medical outcomes and expenses. We found a pretty large difference in individuals with diabetes and their peers," said Jason Fletcher, an associate professor in the division of health policy and administration at Yale University.

The findings are published in the January issue of Health Affairs.

More than 23 million people in the United States have diabetes, according to background information in the report. And, previous research from the American Diabetes Association has shown that direct medical costs average about $6,649 a year for people with diabetes.

However, direct medical costs aren't the only extra expenses faced by people living with diabetes.

The current study used data from the U.S. National Longitudinal Study of Adolescent Health to attempt to assess some of those non-medical costs.

The study began between 1994 and 1995, and surveyed about 15,000 teens in grades 7 through 12. The same students were surveyed again at three different times: in 1996, 2001/2002 and in 2008. At the time of the last survey, the study participants were around 30 years old.

About one-quarter of a percent (approximately 385) of those studied said they had ever been diagnosed with diabetes. They weren't asked which type of diabetes they had. However, in a younger population, type 1 diabetes is the more prevalent type.

After compensating for potential confounding factors, such as other illnesses and family background, the investigators found that people with diabetes completed an average of one-quarter of a school year less than their peers without diabetes.

The researchers also found that having diabetes significantly increased the risk of dropping out of high school, by an average of 6 percent. In addition, people with diabetes were between 8 percent and 13 percent less likely to attend college.

Surprisingly, having a parent with diabetes also seems to impact education and earnings, lowering the chances of attending college by another 4 percent to 6 percent.

Once out of school, having diabetes appears to affect earnings as well. Over a 40-year work lifetime, the study found that people with diabetes make $160,000 less per person than do people without the disease.

Though the study wasn't designed to explore the reasons behind the differences, Fletcher said there are likely many factors at play.

During their school years, people with diabetes tend to have more frequent absences, and while in any given year such absences might not seem like much, they can add up to a substantial amount of missed schooling over time, Fletcher explained.

Absences may also cost people with diabetes in terms of earnings, said Fletcher. And, if someone with diabetes has dropped out of school, it's likely they would earn less at work. Another possibility is something called "job lock," according to the study authors. Fletcher said this occurs when people with diabetes feel like they can't leave their job, even if they don't like it, because they are afraid of losing their health insurance.

"I was surprised and disturbed by the study's findings," said William Polonsky, CEO of the Behavioral Diabetes Institute and an associate clinical professor in psychiatry at the University of California, San Diego.

But, he pointed out, "if these findings are true for this group of kids from the early 1990s, they're probably not anymore." He said that changes in diabetes management over the past 20 or 30 years have made a significant difference in the way people with diabetes live.

"In the past, some people were told by their physicians that they weren't going to live too long, probably not even past 30 or 40," which would certainly have had an impact on how someone would view schooling and long-term career plans, said Polonsky.

Now, most young people with type 1 diabetes can expect to have a normal or close-to-normal life span, he said. And, he added, "It behooves us to get the word out to patients and employers that we can now say, 'With good care, that you can live a longer, healthy life with diabetes.'"

More information

To learn more about the rights of children and teens with type 1 diabetes in school, visit the American Diabetes Association (ADA). The ADA also has information about workplace rights for people with diabetes.