Background The circadian variation pattern of sudden cardiac arrest (SCA) occurred in Chinese community including both community healthcare centres and primary hospitals remains unknown. This study analysed the circadian variation of SCA in the Chinese community.Methods Data between 2018 and 2022 from the remote ECG diagnosis system of Xinhua Hospital affiliated to Shanghai Jiao Tong University School of Medicine were analysed to examine the circadian rhythm of SCA, stratified by initial shockable (ventricular tachycardia or ventricular fibrillation) versus non-shockable (asystole or pulseless electrical activity) rhythm.Results Among 10 210 cases of SCA, major cases (8736, 85.6%) were non-shockable and 1474 (14.4%) cases were shockable. The circadian rhythm of SCA was as follows: peak time was from 08:00 to 11:59 (30.1%), while deep valley was from 00:00 to 03:59 (7.5%). The proportions of events by non-shockable and shockable events were similar and both reached their peak from 08:00 to 11:59, with a percentage of 29.0% and 36.4%, respectively. Multivariable analysis showed that the relative risk of shockable compared with non-shockable arrests was lower between 00:00 and 03:59 (adjusted OR (aOR): 0.72, 95% CI: 0.54 to 0.97, p=0.028) and 04:00 to 07:59 (aOR: 0.60, 95% CI: 0.46 to 0.79, p<0.001), but higher between 08:00 and 11:59 (aOR: 1.34, 95% CI: 1.09 to 1.64, p=0.005).Conclusions In Chinese community, there is a distinct circadian rhythm of SCA, regardless of initial rhythms. Our findings may be helpful in decision-making, in that more attention and manpower should be placed on the morning hours of first-aid and resuscitation management in Chinese community.
