OBJECTIVETo Study the temporal patterns of stroke onset, and to provide insights into the triggers which might cause the acute onset of stroke and to develop preventive strategies.

METHODSUsing a 10-year period of the SINO-MONICA-Beijing study cohort a total number of 700 000 people, aged 25 to 74 years was recruited. The diagnostic criteria exactly followed the WHO MONICA project. Date of the week, season and month occurrence of stroke were ascertained. Percentage of stroke onset on date in the week, season and month were calculated. chi(2) test was used to identify the deviation from expected frequencies. Multiple stepwise regression was carried out for multivariate analysis.

RESULTSMost stroke occurred and recurred (chi(2) = 7.02, P = 0.008 in male and chi(2) = 12.32, P = 0.000 4 in female) in winter. The most frequent occurrence on the dates of stroke events were Monday in the urbans and Saturday in the rurals. The finding were confirmed (the stroke occurrence and recurrence positively correlated with season, correlation coefficient 0.032, P = 0.01) by correlation and multiple stepwise regression.

CONCLUSIONIt was important to find out the circadian variation and the external triggering factors together with unhealthy behaviour of life that would contribute to the prevention and reduction of stroke onset.