High proportion of lacunar strokes at night: the Bergen stroke study.

The main objective of this study was to investigate the circadian distribution of subtypes of ischemic stroke. The time of onset of stroke in consecutive stroke patients was registered and categorized into the following time intervals: midnight-6 am, 6 am-noon, noon-6 pm, and 6 pm-midnight. Patients with unknown onset of stroke were categorized as woke up with stroke, found with stroke by others, and miscellaneous. Patients who woke up with stroke, were included in the midnight-6 am interval. Stroke subtypes were categorized according to the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) criteria and as lacunar or embolic stroke based on diffusion-weighted magnetic resonance imaging (DWI). The study group comprised 1101 patients who sustained ischemic stroke between February 2006 and March 2008. The proportion of lacunar stroke, defined according to both the TOAST criteria and DWI findings, was significantly higher in the midnight-6 am interval compared with the other time intervals. In our study group, the prevalence of lacunar strokes was highest at night.