A history of head injury is common in the United States and is associated With long-term steeper cognitive decline and a greater risk for dementia over the following 20 years than not Having a head injury , new research Suggests.

Although the head injury is known to be associated with short-term cognitive impairment and incident dementia, research on the longer-term cognitive effects has been lacking. For the current analysis, investigators assessed data from participants in the ongoing Atherosclerosis Risk in Communities (ARIC) trial.

"Our study adds to the literature by providing evidence of a large cohort of more than 13,000 individuals followed for a median of 20 years that is common, nearly 25% in this population, and is associated with greater long-term cognitive decline and increased risk of incident dementia, "said lead author Andrea LC Schneider, MD, Johns Hopkins University, Maryland.

20 Years of Data

ARIC is an ongoing prospective cohort study of more than 15,000 adults aged 45 to 65 years from four US communities . The new analysis included the 13,192 participants who were in the study at its first cognitive assessment, which was conducted from 1990 to 1992. The results of this assessment were considered baseline for the current analysis.

To assess participants' cognitive function over time, a global cognitive score was used to represent the results of three cognitive assessments measured during the course of the study, at baseline, from 1996 to 1998, and from 2011 to 2013.

During a follow-up of 20 years, 24% of the participants experienced at least one head injury, determined by self-report and emergency department/hospitalization ICD-9 codes. These injuries ranged from mild concussion, with or without loss of consciousness, to moderate / severe traumatic brain injury.

After adjusting for factors such as age, sex, race, hypertension, and stroke, results showed that decreases in cognitive decline were observed in both the participants who had had head injuries and those who had not.

Those sustaining at least one or more head injuries showed the significantly greater cognitive decline (-1.00; 95% confidence interval [CI], -1.06 to -0.95) than those who had not had a head injury (-0.87; 95% CI, -0.91 to -0.83; difference, -0.13).

In clinical terms, the increased decline for those with a head injury "is equivalent to a person without a head injury being approximately 4 years older at study baseline," Schneider noted. There were 1295 cases of incident dementia overall, determined by using neuropsychological tests, telephone interviews, and hospitalization / death certificate codes. These included 895 patients among those without head injury and 400 patients who had had a head injury.