Severe, Rapid Memory Loss Could Herald Stroke

Caroline Helwick

February 02, 2012

February 2, 2012 — Severe, rapid memory loss may be linked to, and might possibly predict, a future fatal stroke, Harvard researchers report.

"We are most surprised that people who died after strokes had such sharp memory declines years before stroke onset," said Qianyi Wang, who is a graduate student at the Harvard University School of Public Health, Boston, Massachusetts.

"Among stroke survivors, memory decline continued after stroke, with no apparent abatement in the rate of decline," added senior author M. Maria Glymour, SD, of Harvard School of Public Health, who presented the findings at a press briefing.

Dr. M. Maria Glymour

Their results were reported here at the American Stroke Association's International Stroke Conference (ISC) 2012.

Memory Loss Assessed

The investigators used a prospective cohort from the Health and Retirement Study (n = 12,412) to describe the long-term trajectory of memory functioning before and after the occurrence of stroke and compared it with memory changes in stroke-free elderly persons.

To do so, they longitudinally followed 11,814 people aged 50 years and older who were free of stroke at baseline. The participants were examined every 2 years over a period of 10 years for signs of declining memory. The participants continued in the study if they survived a stroke.

Researchers used a standard word-recall list to measure memory loss. For participants with severe impairment, the researchers interviewed spouses or other caregivers using a standardized assessment. The investigators controlled for a number of factors, such as marital status, race, education, and household wealth, among others. The memory score was expressed in standard deviation units.

A total of 1820 strokes were observed. The average memory loss documented each year was compared for participants who remained stroke-free throughout the study; for participants who survived a stroke; and for participants who had a stroke but did not survive.

Although stroke induced large, immediate decrements in memory, differences were apparent years before the onset of the stroke. The baseline memory score was highest for the stroke-free participants (2.63); it was next highest for the stroke survivors (1.83), and lowest for stroke non-survivors (1.21).

The prestroke rate of memory decline among future stroke survivors was similar to the age-related memory decline in adults who remained stroke-free, whereas those who died after their stroke had a faster decline, Dr. Glymour noted.

Trajectory of Memory Loss

In describing the trajectory of memory functioning for survivors of stroke, Dr. Glymour noted that memory declined rapidly each year before the occurrence of stroke, declined suddenly near the onset of stroke, and continued to decline at a slightly faster rate after the stroke.

Regarding the trajectory of memory function for persons who did not survive a stroke, she noted that their memory was declining even more rapidly than was that of survivors of stroke in the 3 to 4 years before the stroke.

"Memory also declined annually among individuals who did not have a stroke during follow-up, but the rate of decline was slower than among individuals who had stroke onset," she added.

The annual age-related memory decline was -0.08 for stroke-free individuals. For stroke survivors, the annual prestroke memory decline was -0.14, with a sudden decrement to -0.32 at the time of stroke; thereafter, their annual poststroke decline was -0.15. Victims of fatal stroke had had an annual prestroke memory decline of -0.21.

Even before the occurrence of their stroke, people who survived a stroke were losing memory at about twice the rate as people without a stroke, the authors note. Non-survivors of a stroke lost memory leading up to the stroke at 3 times the rate, she noted.

The declines are similar to the declines associated with growing 3 to 4 years older among the stroke-free, she noted.

The reasons for these associations are not clear. The investigators suggest that memory decline may be a marker for the development of disease. The other possibility is that memory impairment may render individuals more vulnerable to death in the wake of a stroke for reasons unrelated to the stroke's severity, because memory impairment is associated with increased mortality regardless of stroke. People who die from stroke may also have worse underlying disease status as well.

"We would love to be able to distinguish among these possibilities," Dr. Glymour said.

Challenging Dogma

Steven Greenberg, MD, professor of neurology at Harvard Medical School, Boston, moderated the press briefing here and commented on the study.

"The accepted dogma in many circles is that memory loss has nothing to do with blood vessels, and that 'it's all Alzheimer's disease,' but that dogma has been turned on its head in the past 10 years," he told reporters here.

"The data presented here speak to the intimate link between memory loss and stroke, that they are closely linked," Dr. Greenberg added. "Presumably, some vascular disease is responsible for at least some of the memory loss that we are seeing in these people who then go on to have a fatal stroke."

Mr. Wang, Dr. Glymour, and Dr. Greenberg have disclosed no relevant financial relationships.

International Stroke Conference (ICS) 2012. Abstract #31. Presented February 1, 2012.


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