COPD causes death for approximately 3 million people each year and is the third leading cause of death worldwide in 20191. It seriously affects the patients’ physical and mental health, and brings heavy mental and economic burden to the society, patients and families. Our study was aimed at describing the clinical characteristics of, and the outcomes of AECOPD patients between different gender, to help provide a better understanding of the population and identify certain features that may drive individualised therapy. In this study, we found that woman in the first AECOPD hospitalizations tended to be older, less somker, higher mean BMI, more often had bronchiectasis, lower eosinophils and IgE, better FEV1/FVC ratios, more emphysema, bullae and interstitil chnges, and less likely to use LABA/LAMA/ICS, but there was no clear difference between the two groups in the short-term prognoses. The multivariate logistic regression analysis showed that readmission was independently associated with increased course of disease, combined with chronic pulmonary heart disease, and combined with peptic ulcer but not with sex.
Cigarette smoking is a major cause of COPD. The results of this study show that smoking was performed more commonly on male patients (71.79%) compared to the female patients (2.78%), and similar study findings from abroad also supported this finding8,9. This may explain why COPD prevalence was significantly higher among men than women. Besides this, some research show that COPD is characterized by different phenotypes and clinical presentations. Study shows that biomass fuel is highly prevalent in China and women are still the main bearers of housework so that they have relatively more access to biomass fuel10. It has been reported that smokers are more likely to develop emphysema than those exposed to biomass fuel. Camp et al found that female COPD patients exposed to biomass smoke had less emphysema but more air retention than those exposed to e-tobacco smoke, suggesting that biofuels-induced COPD may be a respiratory tract dominated phenotype11. In this study, we found that men had more emphysema, bullae and interstitil chnges, but lower FEV1/FVC ratios than women, demonstrated these same findings in our study. Therefore, this study shows that different approaches to preventive measures should be taken according to gender.
A crucial pathologic feature of COPD is airway inflammation and remodeling. Eosinophils are pro-inflammatory effector cells which release pleiotropic chemokines, cytokines and cytotoxic granules such as eosinophil peroxidase and eosinophil-derived neurotoxin, play a role in the immune response to inflammation and infection. Couillard et al found the eosinophil count elevated were associated with increased risk of readmission12. The main finding of this study was that the eosinophil count and EOS%≥2% increased in the male patients compared with the female patients, which is consistent with the relevant results from both domestic and foreign studies13,14. This may explain why male patients had a higher hospitalization rate than females. It has been suggested that airway eosinophilia facilitated responsiveness to bronchodilator and steroidal therapies15. In the course of clinical diagnosis and treatment, our study discovered that male patients were more likely to use LABA/LAMA/ICS, it also proves the rationality of clinical treatment. IgE is the major mediator in allergic responses, plays a pivotal role in airway inflammation and remodeling16. Many study suggest that patients with COPD also have higher total IgE levels, and there are gender differences. Study found that elevated serum IgE is associated with the occurrence of exacerbations in men with COPD and with the risk of lung function decline, and they speculate that IgE-mediated pathways might be involved in the pathogenesis of exacerbations in men with COPD and in the pathogenesis of progressive airfow limitation in patients with elevated IgE levels17. This was also found in the studies of Marek et al18, and they also found that there were higher total IgE levels in currently smoking than in not currently smoking men. In this study, the IgE levels of males were significantly higher than in females. Therefore, using antibodies targeting the IgE pathway for COPD may help in the prevention and control of disease, especially among men. But mechanism of gender-related and smoke-related differences in IgE level, further research is still needed.
Complications will also have an impact on the quality of life of COPD patients. Juan et al found that cardiovascular comorbidities such as hypertension and ischemic heart disease, are the most common comorbid combinations in the male patients, and the female patients were the most likely to have metabolic diseases such as osteoporosis19. Maeva et al found that the proportion of subjects with ischemic heart disease and OSA was higher in males, but women tend to experience a greater prevalence of rhinitis and anxiety disorders20. In this study, the prevalence of bronchiectasis in female patients with COPD is higher compared to male patients, were inconsistent with the findings of other study, but we found some abnormalities in metabolism-related indicators between different genders, such as glycosylated hemoglobin and low density lipoprotein, which can also serve as fields for continued in-depth research in the future.
On average, each COPD patients suffers from 0.5 to 3.5 episodes of acute excerbations per year, and AECOPD is a major cause of death and causes huge medical expenditures2. Marshall et al followed up for 3 years, the mortality was 10.8% in females and 11.2% in males, but the difference was not statistically significant5. In a 5-year follow-up study, Tamara et al found women have higher 5-year survival rates than men ( 86.9% vs 76.3%, P<0.001)6. However, we found that the mortality rate was lower but had a higer rate of readmission within 180 days, although the difference in our study did not reach statistical significance. In female group, the rates of time to readmission for 30 days, 90 days, and 180 days from the time of admission were 9.96%, 20.9%, and 23.88%, while the male group were 8.3%, 16.23%, 24.91%, respectively. Therefore, we further investigated the risk factors associated with short-term readmission. Our study found that readmission was independently associated with increased course of disease, combined with chronic pulmonary heart disease, and combined with peptic ulcer but not with sex. As a result, it is necessary to take the necessary measures to reduce readmissions.
Despite these strengths, our study has some limitations. First, as a retrospective study, some information, such as risk factor exposure and objective questionnaires, was incomplete during clinical data collection. Second, the number of cases in this study was relatively small, and the number of patients in the 2 groups was not balanced. This might have influenced the results.