Cardiac disease elevates cognitive impairment risk

As the nation's population grows older, it's increasingly important that physicians be aware of common health problems that can increase patients' risk of developing cognitive impairment, according to researchers at Mayo Clinic.

One such health problem to watch for is cardiac disease, according to a study published online Jan. 28 in JAMA Neurology, formerly Archives of Neurology. Elderly adults with cardiac disease, including atrial fibrillation and coronary heart disease, are 1.8 times more likely to develop non-amnestic mild cognitive impairment , or naMCI, than similarly aged individuals without a heart condition, the study said.

People with MCI experience mild changes in memory and thinking that can progress to Alzheimer's dementia, according to the Alzheimer's Assn. One form of mild cognitive impairment, amnestic MCI (aMCI), primarily affects the memory. The other type, naMCI, impacts thinking skills other than memory, such as the ability to make sound decisions and judge the amount of time needed to complete complex tasks, the association said.

“With the aging of the population, it's likely that we're going to be getting an increasing number of people with dementia because people are living longer,” said Dr. Rosebud O. Roberts, the study's primary author and lead investigator.

“If we can identify conditions or risk factors that lead people to progress to MCI and intervene at that point, we can hopefully prevent their progression to dementia,” said Dr. Roberts, a health sciences researcher at Mayo Clinic in Minnesota.

Likely contributing to the association between cardiac disease and naMCI is that the heart's inability to pump blood properly could reduce the blood supply to the brain and damage blood vessels there, Dr. Roberts said.

Data show that as many as one-fifth of people 65 and older have some form of MCI, according to the Alzheimer's Assn. Nearly half of individuals who visited doctors about MCI symptoms will develop dementia within three or four years, said a study in the June 1999 issue of JAMA Neurology.

Researchers for the latest JAMA Neurology study examined data on 1,450 residents of Olmsted County, Minnesota, who were between the ages of 70 and 89 on Oct. 1, 2004. Participants did not have MCI or dementia at the start of the study. The analysis is part of the Mayo Clinic Study of Aging, a population-based study designed to investigate risk factors for MCI in Olmsted County.

Each participant was evaluated by a physician and received extensive cognitive testing by a psychometrist. Researchers assessed participants' body mass indexes, cognition levels, depressive symptoms, exercise levels, and histories of stroke and cardiac disease. Participants' health was reevaluated during follow-ups, which were performed at 15-month intervals for a median of four years, the study said.

Findings differed based on gender

Researchers found that 348 of the adults developed MCI by the end of the study and 18 developed dementia. Among those individuals with MCI, 66.4% had aMCI, 26.7% developed naMCI and 6.9% developed MCI of an unknown subtype. Incidence of naMCI was nearly two times higher for participants with cardiac disease (23.4 cases of naMCI per 1,000 person-years) than for those without heart problems (12.2 cases per 1,000 person years), the data show.

The association varied by sex, the study said. For instance, women with cardiac disease were significantly more likely to develop naMCI than women without heart conditions. But for men, the risk of developing this cognitive impairment was similar among those with and without cardiac disease, the data show.

The reason there is no difference among men could be because, in general, they have more vascular disease than women, Dr. Roberts said. “Some men whom we didn't define as having cardiac disease might have had other vascular conditions like type 2 diabetes, which also can increase their risk of progressing to MCI.”

Cardiac disease was not associated with aMCI, the study said. One limitation of the report is that the assessed population largely was white, which means the findings might not apply to other demographic groups, researchers said.

Still, the study's findings are significant for primary care physicians, because cardiac disease negatively impacts all ethnic groups, Dr. Roberts said. “It's important for physicians to recognize that heart disease doesn't just affect your general health, but it also [could] increase your risk of MCI.”