Stroke patients on a downhill memory slope

Sep 10 2012

By Eleanor McDermid, Senior medwireNews Reporter

The large memory declines associated with acute stroke are part of a long-term downward trajectory, show findings from the Health and Retirement Study (HRS).

Even before the event, HRS participants who had stroke had significantly steeper memory declines than those who did not.

The HRS participants did an immediate- and delayed-recall memory test every 2 years, which revealed memory declines of an average 0.143 points per year among the 1574 participants who went on to have a stroke. By contrast, the decline was just 0.101 points per year among the 15,766 who remained stroke-free during up to 10 years of follow up.

Memory differences between participants who did and did not have a stroke were apparent up to 4 years before onset. The differences persisted after accounting for variables including age, gender, and age at stroke onset.

"Prestroke memory decline is most likely an early sign of cerebrovascular disease," M Maria Glymour and team, from the Harvard School of Public Health in Boston, Massachusetts, USA, write in Stroke.

"However, it is also plausible that lower memory performance increases vulnerability to clinically manifest stroke. Individuals with very high memory scores may have better cognitive reserve and may be able to sustain an acute ischemic event without severe clinical manifestations."

They note that this difference "has important clinical implications and therefore merits further exploration."

The prestroke rate of memory decline was particularly steep among the 385 people who did not survive their stroke. At 0.212 points per year, this was a significantly steeper decline than that seen among stroke survivors.

"These individuals may have particularly severe underlying cerebrovascular disease that causes very rapid cognitive declines culminating in fatal stroke, or the prestroke cognitive declines may be attributable to causes other than cerebrovascular disease but may render the patient frail or unusually vulnerable to death as a result of the stroke," Glymour et al suggest.

Stroke caused a large decrease in memory performance, of 0.369 points, equivalent to 3.7 years of age-related memory decline among stroke-free participants. But after stroke, memory in stroke survivors continued to decline at a similar rate to that before stroke, at 0.142 points per year.

"This finding may indicate that cerebrovascular risk factors are not adequately controlled after stroke diagnosis, or that acute stroke presages an ongoing, cascading process of neurological injury," say the researchers.

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