ABSTRACT
Objective To investigate the features of time distribution in the onset of aortic dissection (AD).Methods The retrospective cross-sectional study was conducted.The clinical data of 476 AD patients who were admitted to the First Affiliated Hospital of Anhui Medical University from January 2009 to June 2017 were collected.The patients were divided by the following criteria:gender,age [youth(＜45 years),middle-age (45-59 years) and elderly (≥ 60 years)],Stanford types (type A and type B),with or without hypertension.All variables were analyzed by circular distribution statistics to illuminate the features of time distribution in the onset of AD (monthly rhythm and circadian rhythm).Observation indicators:(1) overall time distribution of AD;(2) time distribution of subgroups with different genders;(3) time distribution of subgroups with different age;(4) time distribution of subgroups with different Stanford types;(5) time distribution of subgroups with or without hypertension.Measurement data with normal distribution were represented as (x)±s and count data were described as constituent ratio.The circular distrbution statistics were used to calculate time data of onset after trigonometric function transformation.The monthly rhythm and circadian rhythm were done using the Rayleigh test (Z value).Results (1) Overall time distribution of AD:the AD patients had the monthly rhythm and circadian rhythm (Z=14.79,31.60,P＜0.05).The months with the maximum and minimum cases were November (59 cases) and August (24 cases) respectively,the peak day was on January 12.AD often occurred from 16:00 to 17:00 (37 cases) but barely occurred from 3:00 to 4:00 (8 cases),with a peak of 14:55.(2) Time distribution of subgroups with different gender:male subgroup had the monthly rhythm and circadian rhythm (Z =11.28,27.81,P＜0.05);female subgroup had the monthly rhythm and circadian rhythm (Z=3.48,4.37,P＜0.05).(3) Time distribution of subgroups with different age:patients in the youth subgroup had no monthly rhythm (Z=1.33,P＞0.05),and there was the circadian rhythm (Z=4.29,P＜0.05);patients in the middle-age subgroup had the monthly rhythm and circadian rhythm (Z =7.48,17.41,P＜0.05);patients in the old-age subgroup had the monthly rhythm and circadian rhythm (Z =6.62,11.04,P ＜ 0.05).(4) Time distribution of subgroups with different Stanford type:patients inthe type A subgroup had no monthly rhythm (Z=1.60,P＞0.05),and there was the circadian rhythm (Z=10.51,P＜0.05);patients in the type B subgroup had the monthly rhythm and circadian rhythm (Z=13.94,21.70,P＜0.05).(5) Time distribution of subgroups with or without hypertension:subgroups with hypertension had the monthly rhythm and circadian rhythm (Z =12.08,29.81,P＜ 0.05).Subgroups without hypertension had no monthly rhythm (Z=3.84,P＞0.05),showing a statistically significant difference in the circadian rhythm (Z=4.78,P＜0.05).Conclusion AD often occurs in cold months and afternoon.