A new article in the journal Neurology from the Whitmer Lab has found a significant increase in the risk of dementia among people with type 1 diabetes who experience a traumatic brain injury. This is the first study of traumatic brain injury and dementia in those with type 1 diabetes.

“People with type 1 diabetes are a group that only relatively recently began living to old age. This presents new challenges because they’re much more likely to fall and this could result in a  brain injury, which our study shows is a risk factor for dementia, but falls can be a modifiable risk factor for dementia if they can be prevented.” - Professor Rachel Whitmer, PhD

The study of 4,049 people with type 1 diabetes found that people who experienced a traumatic brain injury had a 3.6-times higher risk of developing dementia than those without a traumatic brain injury. Falls are the most common cause of traumatic brain injuries, and older people with type 1 diabetes are at an elevated risk of falling, possibly due to diabetes-related complications. The research findings suggest that traumatic brain injuries could lead to a downward spiral of diminishing mental and overall health as people with type 1 diabetes grow old.

“This is the first time the association between traumatic brain injuries and dementia has been studied in people with type 1 diabetes,” said the study’s lead author Paola Gilsanz, ScD, a researcher at Kaiser Permanent Northern California’s Division of Research. “It’s really important to understand this association because people with type 1 diabetes are living longer than ever before and are entering an age group at risk for dementia, which is particularly concerning because of the amount of self-care necessary to manage type 1 diabetes.”

The study, titled “Traumatic brain injury associated with dementia risk among people with type 1 diabetes,” was published September 26, 2018 in the online issue of Neurology, the medical journal of the American Academy of Neurology.

Approximately 2 million people in the United States sustain a traumatic brain injury each year, according to 2010 data from the Centers for Disease Control and Prevention. Falls are the most common cause of these injuries and contributed to 47 percent of traumatic brain injury emergency room visits, hospitalizations and deaths. People with type 1 diabetes are at increased risk of falls, possibly due to diabetic complications. The new study only looked at people with type 1 diabetes, but people with type 2 diabetes have similar complications that could also put them at an increased risk of falls.

The study analyzed data from 4,049 members of Kaiser Permanente Northern California with type 1 diabetes, but without dementia at the start of the study, who were at least 50 years old. Their history of traumatic brain injury was assessed at the start of and throughout the study, which included data from 1996 to 2015.

A total of 178 people experienced a traumatic brain injury. Of the people experiencing a traumatic brain injury, 13 percent (23 people) then developed dementia. When accounting for variables like age, sex, comorbidities, and health indicators, traumatic brain injuries were associated with 3.6-times the dementia risk.

Comparing this risk to the risk in the general population is difficult due to differences in study designs, but the new study suggests that the harmful effect of traumatic brain injuries on dementia risk may be greater among individuals with type 1 diabetes than the general population.