What causes increased stroke mortality in patients with prestroke dementia?

In patients with dementia, the incidence of stroke is higher and strokes are more severe and lethal. The purpose of this population-based study was to describe in what way previous dementia affects mortality in stroke patients.

Subjects were all persons > or =65 years old who had a first-ever stroke during 1 year (n = 327). The prestroke dementia (PSD) diagnosis was made at the time of the stroke diagnosis using data from next of kin and from patient records. Patients were followed prospectively and causes of death were evaluated.

The 28-day case fatality was 44% for PSD patients and 15% for non-PSD patients. Corresponding ratios at 1 year were 71 and 36%, respectively. Twenty-eight percent of the PSD patients had a new stroke during the first year, compared to 8% of the non-PSD patients. More patients in the PSD group died as a direct or indirect consequence of their stroke. Multivariate analysis showed that PSD, in addition to age, atrial fibrillation and stroke severity, was an independent predictor of mortality.

The PSD patients more often had a stroke-related death, even when we adjusted for a number of other factors. The cause for this is most likely multifactorial, including an increased tendency to contract complications in the acute phase, and iatrogenic causes. The brain of the PSD patients may also be frailer and more susceptible to ischemic or hemorrhagic damage than the nondemented brain.