Prevalence of chronic obstructive pulmonary disease (COPD) among rheumatoid arthritis: results from national inpatient database

Figures & data

Table 1. Demographic characteristics of rheumatoid arthritis hospitalizations compared to those without rheumatoid arthritis from the National Inpatient Sample (2013).

		Before nearest-neighbor propensity matching				After nearest-neighbor propensity matching
	Total	RA hospitalizations	Non-RA hospitalizations	p-Value	Total	RA hospitalizations	Non-RA hospitalizations	p-Value
No of observations in the sample (n)	5,984,453	93,750	5,890,703		375,000	93,750	281,250
Weighted estimate, N (%)	29,922,246 (98.43)	468,750 (1.57)	29,453,496 (98.43)		1,874,999	468,750 (25)	1,406,249 (75)
Sex, N (%)								1
Male	12,270,187 (41.01)	121,965 (26.02)	12,148,222 (41.25)	<0.0001	487,860 (26.02)	121,965 (26.02)	365,895 (26.02)
Female	17,652,059 (58.99)	346,785 (73.98)	17,305,274 (58.75)		1,387,139 (73.98)	346,785 (73.98)	1,040,354 (73.98)
Age
Mean (se)		67.46 (0.08)	57.19 (0.10)	<0.0001		67.47 (0.06)	67.47 (0.08)	1
Age Category, %				<0.0001
18–34	20.07	3.00	20.34		3.00	3.00	3.00	1
35–64	39.29	35.82	39.35		35.82	35.82	35.81
>65	40.64	61.19	40.31		61.19	61.19	61.19
Race, %				<0.0001				<0.0001
Caucasians	68.67	76	68.55		73.83	76	73.11
African American	14.73	11.95	14.78		13.04	11.95	13.40
Others	16.6	12.05	16.67		13.13	12.05	13.49
Charlson Comorbidity Index, %				<0.0001				<0.0001
0	41.35	0.76	42		22.58	0.76	29.85
1	20.67	29.78	20.53		24.99	29.78	23.39
≥2	37.98	69.46	37.47		52.43	69.46	46.76
Smoking hx %	26.13	28.88	26.09	<0.0001	26.94	28.88	26.30	<0.0001
COPD prevalence, %	13.53	21.12	13.41	<0.0001	18.72	21.12	17.92	<0.0001

Table 2. Univariate and multivariate logistic regression analyses for prevalence of chronic obstructive pulmonary disease (COPD) in patients with rheumatoid arthritis (RA).

	Unadjusted OR	Adjusted* OR
Unmatched population (before near-neighbor propensity matching)	1.73 (95% CI 1.70–1.76), p < 0.0001	1.28 (95% CI 1.26–1.31), p < 0.0001
Matched population (after near-neighbor propensity matching)	1.23 (95% CI 1.20–1.25), p < 0.0001	1.20 (95% CI 1.17–1.22), p < 0.0001

* Adjusted for age, gender, race and smoking status.

CI: confidence interval; OR: odds ratio.