Patients with ischemic heart disease (IHD) are prone to gastrointestinal bleeding (GIB) under stress and other stimuli, and in turn severe GIB can induce IHD. IHD patients complicated with GIB are facinga higher mortality risk than those with IHD or GIB alone. Season and temperature may increasethe morbidity and mortality risk of patients with IHD and GIB, but further research is stillneeded.

To investigate the seasonal distribution characteristics of IHD complicated with GIB and its correlation with temperature.

A total of 730 IHD patients complicated with GIB treated at West China Hospital, Sichuan University, from January 2014 to December 2018 were enrolled as the research objectsbased on inclusion and exclusion criteria. The following baseline data of the patients were collected through the electronic medical record system, including age, sex, history of smoking, drinking, percutaneous coronary intervention (PCI) , use of antiplatelet agents and use of anticoagulants; presence or absence of hypertension, diabetes mellitus, chronic kidney disease (CKD) and chronic obstructive pulmonary disease (COPD) ; time of admission, IHD type (stable angina pectoris and acute coronary syndrome) , GIB site (nonvariceal upper GIB, variceal upper GIB, lower GIB and unexplained GIB) and mode of discharge (death outcome) . The meteorological dataincluding monthly average high temperature, monthly average low temperature, monthly average temperature and monthly temperature difference from January 2014 to December 2018 in Chengdu were obtained from the Chengdu Meteorological Office. Based on the commonly adopted seasonal division method in climatology and meteorological characteristics of the Chengdu area, the seasons were divided into spring (March, April and May) , summer (June, July and August) , autumn (September, October and November) and winter (December, January and February) . The seasonal hospitalization rate, seasonal incidence of acute coronary syndrome, seasonal incidence of bleeding sites and seasonal mortality of IHD patients complicated with GIB were analyzed.

The participants included 493 males and 237 females (male-to-female ratio: 2.08∶1) with an average age of (72.8±11.3) years. The proportions of males and females aged 70-79 were higher, which were 35.29% (174/493) and 39.66% (94/237) , respectively. The temperature was highest in July and August and lowest in December and January. The greatest temperature difference occurred in spring. The hospitalization rate was higher in winter and spring than in summer and autumn (58.8% vs 41.2%, χ²=3.907, P=0.003) . Compared with summer and autumn, the hospitalization rate for IHD patients complicated with GIB increased in spring (χ²=2.912, P=0.020; χ²=2.567, P=0.033) . In addition, the hospitalization rate for IHD patients complicated with GIB increased in winter compared with that in summer (χ²=2.191, P=0.035) . The Spearman correlation analysis results indicated that the number of hospitalized IHD patients complicated with GIB was negatively correlated with the monthly average temperature (r_s=-0.280, P<0.05) and positively correlated with the monthly temperature difference (r_s=0.260, P<0.05) . Compared with summer and autumn, the incidence of acute coronary syndrome in patients with IHD combined with GIB was higher in winter (χ²=3.755, P=0.006; χ² =3.167, P=0.013) ; the incidence of acute coronary syndrome in patients with IHD combined with GIB in spring was higher than that in summer and autumn (χ²=3.108, P=0.015; χ²=2.520, P=0.036) . Compared with summer and autumn, the incidence of non-variceal upper gastrointestinal bleeding increased in winter (χ²=2.963, P=0.018; χ² =2.528, P=0.035) ; the incidence of non-variceal upper gastrointestinal bleeding in spring was higher than that in summer and autumn (χ²=3.056, P=0.016; χ²=2.620, P=0.031) . Compared with summer and autumn, the incidence of lower gastrointestinal bleeding in winter was higher (χ²=2.773, P=0.024; χ²=2.973, P=0.018) ; the incidence of lower gastrointestinal bleeding in spring was higher than that in summer and autumn (χ²=2.757, P=0.025; χ²=2.957, P=0.018) ; the incidence of unexplained GIB in winter was higher than that in summer (χ²=2.449, P=0.040) . Compared with that in spring, summer and autumn, the mortality rate for IHD patients complicated with GIB was higher in winter (P<0.05) .

The morbidity of IHD patients complicated with GIB shows obvious seasonality and is influenced by the monthly average temperature and temperature difference, among seasonal and meteorological factors. A decrease in the monthly average temperature or an increase in the temperature difference increases the risks of acute coronary syndrome, nonvariceal upper GIB, lower GIB, unexplained GIB and mortality in IHD patients complicated with GIB.