Accepted on 18 Jun 2019
Submitted on 18 Jun 2018
To determine the relationship between obesity and thirty-days readmission, mortality, morbidity, and health care resource utilization in patients admitted to hospitals in the in the United States with acute exacerbation of chronic obstructive pulmonary disease (AE-COPD).
A retrospective study was conducted using the AHRQ-HCUP Nationwide Readmission Database for the year 2014. Adults (≥ 18 years) with a primary diagnosis of AE-COPD, along with a secondary diagnosis of obesity were identified using ICD-9 codes as described in the literature [1, 2]. The primary outcome was the rate of all-cause readmission within 30 days of discharge. Secondary outcomes were reasons for readmission, readmission mortality rate, morbidity, and resource use (length of stay and total hospitalization costs and charges). Propensity score (PS) using the 1:1 nearest neighbor matching without replacement was utilized to adjust for confounders [3]. Independent risk factors for readmission were identified using a Cox proportional hazards model [4].
In total, 1.5 million hospital admissions among adults with a primary and secondary diagnosis of AE-COPD were identified, of which 14.6% were obese. After PS matching with similar demographic (age, gender, hospital status, etc.) and clinical characteristics (Charlson comorbidity score), 497,897 obese AE-COPD patients were paired with 497,897 non-obese AE-COPD patients. The 30-day rate of readmission among obese and non-obese with AE-COPD were 12.2% and 12.1% (p < 0.001). The most common readmission for both groups was sepsis (20.5%).
During the index admission for AE-COPD, the length of stay (LOS) among obese patients was significantly longer than the non-obese counterparts (5.1 vs 4.3 days, p <0.001). Furthermore, the total cost for the obese patients was more ($10,192 vs $8,889, p <0.001). Most importantly, obese patients’ in-hospital mortality rate during their index admission was significant higher (1.18% vs 0.21%, p < 0.001).
Amongst those readmitted, obese patients similarly had a significant longer length of stay (LOS) than their non-obese counterparts (5.9 vs 4.9 days, p <0.001) and their total cost for the readmission was more expensive ($12,581 vs $10,419, p < 0.001). Lastly, obese patients’ in-hospital mortality rate during their readmission was significant higher (2.89 % vs 0.41%, p < 0.001).
Obesity (HR 1.11, CI 1.06–1.16, p <0.001) was an independent predictor associated with higher risks of readmission. Other medical comorbidities also increased risk of readmission, including atrial fibrillation, acute respiratory failure, acute kidney injury, in-hospital oxygen requirement.
In this study, obese patients admitted with AE-COPD have a higher 30 days of readmission rate, LOS, total hospital cost, and in-hospital mortality (p <0.001) than their non-obese counterparts.
Table 1
Patients and Hospitals Characteristics after Propensity Match.
| Variables | Obese Patients | Non-Obese Patients | P-value | ||
|---|---|---|---|---|---|
| Age | 55.867 | 55.91 | 0.006 | ||
| Gender | 0.54 | ||||
| Female | 63.4 | 63.37 | |||
| Male | 36.6 | 36.63 | |||
| Insurance | 0.8022 | ||||
| Medicaid | 19.33 | 19.32 | |||
| Private | 30.96 | 31.01 | |||
| Self pay | 3.67 | 3.63 | |||
| Median household income | |||||
| $1–$39,999 | 27.36 | 27.36 | 0.468 | ||
| $40,000–$50,999 | 23.35 | 23.34 | |||
| $51,000–$65,999 | 19.35 | 19.33 | |||
| $70,000+ | 22.33 | 22.54 | |||
| Ownership of hospital | 0.661 | ||||
| Government | 73.29 | 73.35 | |||
| Private | 15.35 | 15.33 | |||
| Hospital urban-rural | 0.001 | ||||
| Urban | 33.49 | 33.46 | |||
| Rural | 4.82 | 4.77 | |||
| Others | 1.3 | 1.25 | |||
| Teaching status of hospital | 0.079 | ||||
| Teaching | 63.65 | 63.71 | |||
| Non-teaching | 6.12 | 6.03 | |||
| Hospital bed-size | 0.048 | ||||
| Small | 14.65 | 14.57 | |||
| Medium | 29.02 | 29.02 | |||
| Large | 56.33 | 56.41 | |||
| Charlson comorbidity index | 0.761 | ||||
| 1 | 23.22 | 23.21 | |||
| 2 | 17.01 | 16.97 | |||
| 3 | 32.45 | 32.47 | |||
Table 2
Index admission for Acute Exacerbation of COPD after Propensity Match.
| Variables | Obese Patients | Non-Obese Patients | P-value |
|---|---|---|---|
| Length of Stay | 5.06 (5.00–5.12) | 4.36 (4.26–4.46) | 0.001 |
| Total Hospital Cost | $10,192 (10,007–10,378) | $8,889 (8,623–9,156) | 0.001 |
| Mortality | 2,303 (2,105–5,501) | 420 (350–489) | 0.001 |
Table 3
Readmission for Acute Exacerbation of COPD after Propensity Match.
| Variables | Obese Patients | Non-Obese Patients | P-value |
|---|---|---|---|
| Length of Stay | 5.93 (5.78–6.08) | 4.97 (4.65–5.09) | 0.001 |
| Total Hospital Cost | $12,581 (12,193–12,969) | $10,419 (9,573–11,265) | 0.001 |
| Mortality | 685 (588–782) | 99 (68–130) | 0.001 |
Table 4
Independent Predictors for 30-day Readmission using Propensity Matching.
| Variables | Adjusted Hazard Ratio | 95% Confidence Interval | P-value |
|---|---|---|---|
| Atrial Fibrillation | 1.45 | 1.37–1.53 | 0.001 |
| Acute Respiratory Failure | 1.20 | 1.14–1.26 | 0.001 |
| Acute Kidney Injury | 1.33 | 1.26–1.40 | 0.001 |
| O2 requirement | 1.42 | 1.35–1.51 | 0.001 |
| Obesity | 1.08 | 1.01–1.15 | 0.02 |
| Non-Obesity | 0.92 | 0.86–0.98 | 0.02 |
Table 5
The Most Common 5 Principal Diagnosis for Readmission.
| Diagnosis | ICD-9 | Percentage (%) |
|---|---|---|
| Pneumonia, organism unspecified | 486 | 46.55% |
| Obstructive chronic bronchitis with (acute) exacerbation | 491.21 | 30.29% |
| Obstructive chronic bronchitis with acute bronchitis | 491.22 | 8.07% |
| Influenza with other respiratory manifestations | 187.1 | 2.19% |
| Unspecific bacteria Pneumonia | 482.9 | 1.89% |
| Influenza with pneumonia | 487.0 | 1.89% |
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