Silent cerebral infarction in a community-based autopsy series in Japan. The Hisayama Study

The purpose of this study was to assess the prevalence and characteristics of silent cerebral infarction in a population-based consecutive autopsy series of residents of Hisayama, Kyushu, Japan.

Autopsy records, cerebral pathological findings, and clinical charts of 966 Hisayama residents recorded during the 26 years from 1961 to 1987 were examined (autopsy rate, 82.4%). The subjects were divided into three groups: those with both clinically apparent strokes and pathologically verified cerebral infarcts (stroke group), those having pathological evidence of cerebral infarction in the brain but without clinical stroke episodes (silent infarction group), and those with neither infarction nor stroke episode (noninfarction group). Risk factors and brain pathology in the three groups were compared.

Silent cerebral infarction was found in 12.9% of the 966 subjects who had undergone autopsy, and its frequency increased with age. The subjects with silent infarcts were older, had higher systolic or diastolic blood pressure, and had atrial fibrillation more frequently than subjects in the noninfarction group. There were no significant differences in the locations of infarcts between the stroke and silent infarction groups, although infarcts tended to be located in the deeper area of the brain in the latter. The number and size of infarcts were smaller in the silent infarction group than in the stroke group.

Diastolic blood pressure and atrial fibrillation appear to be strong predictors of silent cerebral infarction in the Japanese general population. Stroke becomes clinically apparent as infarct volume increases.