Impact of clinical factors on hospital stay and hospital readmission rate after acute exacerbation of COPD: a retrospective cross-sectional study

Introduction

Chronic obstructive pulmonary disease (COPD) is now one of the top three causes of death worldwide and 90% of these deaths occur in low- and middle-income countries. More than three million people died of COPD in 2012 accounting for 6% of all deaths globally.¹ It is a condition with high morbidity and cost to health services. Hospitalizations due to COPD negatively affect the well-being of patients with an impact on length and quality of life. Patients with COPD undergo frequent exacerbations which are defined as an acute worsening of respiratory symptoms (increased dyspnea, increased sputum purulence and volume, together with increased cough and wheeze) that results in additional therapy.¹ The length of hospital stay for an acute exacerbation of COPD is related to several factors; these include age, disease severity, the presence of comorbidities, dyspnea perception, respiratory rate, and the need for mechanical ventilation or an intensive care unit. Other variables, such as admissions at the weekend and social factors, have also been considered relevant.² Similarly, hospital readmission after discharge of a COPD patient is affected by many factors. The commonest risk factors for all-cause readmissions within 30 and 90 days are comorbidities, previous exacerbations, hospitalizations, and increased length of stay during the initial admission.³ Gender differences also play a role in the hospital readmission rate.⁴ Understanding these influences, we can suggest strategies targeting culprit factors so that hospital stays, and readmission rates can be minimized. Thus, the economic burden on society and the psychological effect on the patient can be avoided. Our study aimed to identify the differential effects of patient-related factors and treatment factors on the length of hospital stay and hospital readmission rate for exacerbation of COPD-related admissions.

Methods

Results

A total of 151 participants admitted with acute exacerbation of COPD, were enrolled for the study which met the inclusion criteria. Table 1 shows the age of participants ranged from 46 to 94 years with a mean age of 73.54±11.01. Out of 151 participants, 50 (33.10%) belonged to the 70–79 years age group followed by 48 (31.8%) in the 80–89 years age group; 34 (22.5%) in the 60–69 years age group. The least accounted for the age group 40–49 years, which was only 4 (2.6%). Our study revealed sex distribution of female preponderance (94, 62.3%) with a sex ratio of 1:1.64.

The data in Table 2 demonstrates, only a few of the admitted patients (34, 22.5%) had a history of hospital admission related to exacerbation during the last 30 days.

The average hospital stay was 8.3±3.1 days with a range of 1–16 (15 days) (7.78–8.82) at 95% CI). While a proportion of hospital stays of fewer than seven days was found in 49% (74) of patients with acute exacerbation of COPD, 51% (77) were admitted for more than 7 days before discharge Table 3.

Table 4 reveals that the comorbidities were found in 110 (72.8%) participants. Most participants were previous smokers (97 (64.2%)), and 41 (27.2%) were current smokers. However, 13 (8.6%) patients had no history of smoking. During the time of admission, 81 patients had grade III category on mMRC dyspnea scale while the remaining had grade IV (46.4%,70). The hospital record section revealed that 40 (26.5%) people altogether underwent mechanical ventilation with intubation during treatment. Previous exacerbation and admission were found in 114 (75.5%) patients. Similarly, only a few patients (40, 26.5%) with COPD exacerbation were on long-term domiciliary oxygen therapy. The physician required inpatient administration of diuretics among 71 (47.0%) patients.

According to Table 5 the clinical factors associated with prolonged hospital stays (>7 days) during acute exacerbation of COPD patients, were analyzed using the binary logistic regression model. Comorbidities were found significantly associated (more than four times) with prolonged hospital stays in COPD (OR 4.4, 95% CI: 1.32–15.09). The smoking status also has a great impact on prolonged hospital stays. Current smoking was associated 41-times more with prolonged hospital stay (OR 41.59, 95% CI: 7.13–242.63).

As per Table 6, the age group 80–89 years, 70–79 years, and 60–69 years were found to have a most of the admission rate of 12 out of 34 (35.3%), nine out of 34 (26.4%), eight out of 34 (23.5%), respectively, within the last month of admission. Similarly, female participants (n=23); hospital stay more than seven days (n=25), the presence of comorbidities (n=25), current smoker (n=15)/ex-smoker (n=16); MMRC grade IV (n=22), no requirement of mechanical ventilation (n=21), participant without long term oxygen therapy (n=18) and use of diuretics (n=18) represented the maximal proportion of patients. However, mechanical ventilation (OR 48.77, 95% CI: 9.08–261.86) and long-term oxygen therapy (OR 5.37, 95% CI: 1.75–16.49) was concluded to be associated significantly with high hospital admission.

Discussion

COPD is common in chronic smokers. Our study showed the average age of participants admitted with COPD exacerbation was 73.54 years with the predominant 70 to 79 years age group. A retrospective study showed the mean age at COPD diagnosis was 68.1 years in the year 2000 while it was 66.7 years in 2009.⁸ Another retrospective study conducted in Sweden demonstrated the median age at COPD diagnosis being 74 years (range=34–95).⁹ Moreover, this study showed female patients had a high percentage of COPD exacerbation whereas a similar study done in Sweden found similar findings. The study concluded, COPD was more prevalent among women (53.8%) and women with COPD experienced more exacerbations with respect to men (6.66 versus 4.66).¹⁰ The average hospital stay duration during COPD exacerbation was 8.3±3.1 days. However, the average duration was high in a retrospective study performed in the Macao population (12.28±9.23) days.¹¹

Furthermore, the duration of hospital stay was almost equally distributed among the less than 7 days and more than seven days categories in our study. The current results are very similar to a study conducted (84, 51% prolonged stay >7 days) in Sismanogleio General Hospital, Greece.¹²

The study revealed that the age group 80–89 years represented the highest proportion of patients with prolonged hospital stays. But the former study showed the highest population of patients with prolonged stay belonged to age 72.3–79.0 years.¹² Female patients with COPD were found to have stayed hospital prolonged (61%) before discharge. The conclusions drawn were the same in another study led by Hatice et al. who concluded that female patients are more prone to have severe exacerbations, a higher number of hospitalizations, and prolonged lengths of stay for hospitalization.¹³ Another factor found significantly (four times) associated with prolonged hospital stay was comorbidities. A hospital-based study in the USA confirmed that having at least one comorbidity was associated with a 13% greater length of stay (IRR=1.13, 95% CI 1.11–1.15).¹⁴ Study findings are further supported by evidence from another cross-sectional study done in tertiary care centers in 2013. It explains a significant association between mean hospitalizations and the presence of comorbidities (p<0.05).¹⁵ Our retrospective study demonstrated a significant association between COPD exacerbation-related prolonged hospital stay and current smoking habit (49%) as compared to nonsmokers and ex-smokers. On the other hand, a cohort study in the USA concluded that in comparison to current smokers, ex-smokers had a significantly reduced risk of COPD exacerbation after adjusting for age, comorbidities, markers of COPD severity, and socio-economic status.¹⁶ A Nepali cross-sectional retrospective study in a teaching hospital showed a number of comorbidities (p=0.01), dyspnea grade at presentation (p<0.001), eosinophil percentage (p=0.017), use of inhalational medications (p=0.007) and the use of mechanical ventilation (p<0.001) had a significant association with length of hospital stay.¹⁷ Furthermore, the previous exacerbations have a high propensity (80%) to cause longer hospital stays. But another study demonstrated patients with ≥1 previous acute exacerbation of COPD requiring hospitalization, the prolonged hospital stay was seen in 38% of patients as compared to 28% of participants who had a normal stay (p=0.029).¹⁸ The proportion in our study accounts for twice higher.

The proportion of patients who had readmission within 30 days constituted 22.5% in this current study which is higher than a retrospective study done in Beijing that revealed the proportion as 15.8%¹⁹ but very similar to a study done in Korea that showed the readmission percentage was 26.4%.²⁰ Our observational study found the age group 80–89 years had the highest proportion of readmission rate (35%). The results are supported by a systematic review and meta-analysis that describes older patients with COPD typically had a greater likelihood of being readmitted.²¹ The likely reason may be the effect of ageing on residual lung function. This study demonstrates the higher readmission rate among females. On the contrary, the male participants were found of the highest proportion of COPD readmission.²² Similarly, the presence of one or more comorbidities, previous prolonged hospital stays, and long-term oxygen therapy stood as predominant findings for higher readmission in our study. The findings are similar to a prospective study that elaborates the commonest risk factors for all-cause readmissions within 30 and 90 days were comorbidities, previous exacerbations, hospitalizations, and increased length of stay during the initial admission.³ Another study done in South Korea showed that higher re-admission rates were associated with male sex, admission to district hospitals, medical aid recipients, and a longer hospital stay which further supports the evidence.²² Another Chinese study found Education level, smoking status, coronary heart disease, hospitalization times of acute exacerbation of COPD in the past one-year, long-term home oxygen therapy, regular medication, nutritional status, and seasonal factors were the influencing factors for readmission.²³ Previous use of mechanical ventilation was associated significantly with a higher rate of readmission.

Conclusion

Although there is a multitude of factors including many confounding factors affecting the duration of hospital stays, our study was only able to correlate with confidence with comorbidities status, current smoking habits, higher grade of mMRC dyspnea scale, mechanical ventilation, and long-term oxygen therapy. The physician may consider these facts to minimize the risk factors to decrease the duration of hospital stay and hence decrement in hospital costs. Understanding these influences will help optimize care for COPD patients needing hospital admissions.