By Serena Gordon
MONDAY, July 20, 2015 (HealthDay News) -- People with type 1 diabetes may face a greater risk of developing thinking and memory problems as they age compared to the general population, new research suggests.
"Our study found a modestly higher risk of all-cause dementia in people with type 1 diabetes. The next step is to figure out what that means, and how we can help people with type 1 diabetes age successfully," said study author Rachel Whitmer, a senior scientist in the division of research at Kaiser Permanente in Oakland, Calif.
However, Whitmer also noted that the study doesn't prove that type 1 diabetes caused dementia, only that the two diseases were linked. "This is an observational study that shows association, not causation. We don't have tissue from these people's brains," she added.
Whitmer plans to present the findings Monday at the Alzheimer's Association International Conference, in Washington D.C. Findings presented at meetings are generally viewed as preliminary until they've been published in a peer-reviewed journal. Funding for the study was provided by the U.S. National Institute on Aging.
Previous research has shown a link between type 2 diabetes and dementia risk. Since people with type 1 diabetes are now routinely living into their senior years, Whitmer and her colleagues wondered if the same would be true for people with type 1 diabetes.
Although both type 1 and type 2 diabetes cause problems with blood sugar regulation, the root cause of each disease is different. In type 1 diabetes, the immune system mistakenly attacks insulin-producing beta cells in the pancreas. This leaves people with type 1 diabetes with little to no insulin, according to the American Diabetes Association (ADA).
Insulin is a hormone that's necessary for the cells in the body to be able to use carbohydrates from foods as fuel. In type 2 diabetes, the body develops resistance to insulin and doesn't use carbohydrates effectively, the ADA said.
For the study, the researchers reviewed records from all of Kaiser Permanente's Northern California members. They found more than 490,000 who were over 60 years old and had no history of dementia as of 2002. The researchers collected information from 2002 through mid-2014.
From this larger group, they found 334 people with type 1 diabetes. During the study period, 16 percent of the people with type 1 diabetes developed dementia. Whitmer said that they looked for all types of dementia, including Alzheimer's disease and vascular dementia.
In the rest of the group, 12 percent of people developed dementia, the researchers found. The rate of dementia in people with type 2 diabetes in the study was nearly 15 percent, Whitmer said.
"Four percent more of people with type 1 diabetes than the whole sample developed all-cause dementia. We're not seeing something like double the risk, but this is a real increase," Whitmer said.
When the researchers removed people with type 2 diabetes from the general population sample, the association between type 1 diabetes and dementia became even stronger.
However, when the researchers further adjusted the data to account for factors such as sex, age, race, stroke, peripheral artery disease and high blood pressure, the link between type 1 diabetes and dementia decreased. After these adjustments, people with type 1 diabetes were 73 percent more likely to have dementia than the rest of the group.
Whitmer said it's possible that as in type 2 diabetes, high blood sugar levels may cause some sort of damage to blood vessels that could contribute to dementia in people with type 1 diabetes. But the reason behind the association isn't clear from this study, and more research is needed, she said.
"The correlation with type 2 and dementia is so strong, but a correlation with type 1 diabetes hadn't yet been shown," said Helen Nickerson, the director of translational research for JDRF (formerly the Juvenile Diabetes Research Foundation).
And while the current study does find an association, Nickerson said that it raised more questions than it answered. For example, she said, do people with better blood sugar management have less dementia than people whose blood sugar is less well controlled? She said it's also important to note that the study's type 1 diabetes sample size wasn't large.
Still, she said, "Some people with type 1 have insulin resistance to varying degrees [in addition to type 1 diabetes], and that may be the connection. It's something important to look at."
One factor Nickerson thinks probably isn't related to the development of dementia is low blood sugar (hypoglycemia). "People with type 1 diabetes can get a lot of hypoglycemia, so if hypoglycemia were involved, I imagine you would've seen a stronger association," she said.
Both Whitmer and Nickerson agreed that until more study is done to define the connection between type 1 diabetes and dementia, it's a good idea to improve blood sugar control and keep blood pressure and cholesterol levels in check.
Whitmer added that it's important that this issue "is on the radar of clinicians. Type 1 diabetes is a disease that requires constant vigilance and constant self-care. We need to understand how cognition is affected with age."
Both experts also pointed out that this study population was born in the 1940s or earlier, and likely diagnosed with type 1 diabetes quite a while ago. Management of the disease has changed significantly since then, so these findings may not apply to people who've been diagnosed with type 1 diabetes more recently.