Circadian pattern of onset of ischaemic and haemorrhagic strokes, and their relation to sleep/wake cycle.

OBJECTIVE To determine whether there is a circadian pattern of onset of ischaemic and haemorrhagic strokes, and their relation to sleep/wake cycle. METHODS A descriptive study with prospective data was conducted at the Combined Military Hospital Lahore from Jan 2004 to Dec 2007. Eight hundred patients above 26 years of age who had their first ever stroke were included in the study. Strokes were classified into cerebral infarction (CIF), intra-cerebral bleed (ICB) and subarachnoid haemorrhage (SAH). Diagnosis was confirmed either by CT or MRI scan of brain. RESULTS Out of 800 patients, 80% were males and 20% were females. There were 438 (55%) cases of CIF, 329 (41%) of ICB and 33 (4%) of SAH. The age of the patients ranged from 26 to 84 years. Of all stroke cases, 592 (74%) occurred when the patients were awake and 208 (26%) occurred during sleep (p < 0.001). ICB cases showed significant variation with respect to wake/sleep cycle (p < 0.001). In CIF and SAH cases there was insignificant association with wake/sleep state of the patient, (p < 0.180 and 0.792 respectively). Of all strokes 22.5% occurred between 4 am - 8 am, followed by 20.7% between 4 pm - 8 pm, 20.1% between 8 am - 12 noon, 19.5% between 12 noon to 4 PM, 12.7% between 12 midnight and 4 am while 4.3% cases occurred between 8 pm and 12 midnight. The maximum number of CIF (28.5%) occurred between 4 am- 8 am, maximum ICB (29.8%) between 8 am to 12 noon and maximum SAH (30.3%) between 4 pm - 8 pm. The CIF and SAH cases showed smaller peaks between 4 pm to 8 pm and 8 am to 12 noon respectively. The lowest number of ICB cases (4.9%) were around mid night. Significant circadian variation was found in CIF and ICB patients (p < 0.001), however it was insignificant for SAH cases (p = 0.391). CONCLUSION The findings of this study confirm the presence of circadian variation among cases of ischaemic stroke and intra cerebral bleed while no circadian variation was found in subarachnoid haemorrhage. CIF, ICB and SAH predominantly occur in early morning hours, late morning hours and in late afternoon to early evening respectively. Only intracerebral bleed was affected by wake/sleep state.