Evaluation of Risk Factors for Chronic Obstructive Pulmonary Disease in the Middle-Aged and Elderly Rural Population of Northeast China Using Logistic Regression and Principal Component Analysis

Figures & data

Table 1 Main Demographics, Disease History, Environmental Exposure, and Serum Indices Between Patients with Chronic Obstructive Pulmonary Disease and Controls

Characteristics n (%)/(Median, Range)	FEV1/FVC<70% (471)	FEV1/FVC≥70% (485)	X2/t/Z-value	P-value
Sex	471	485	0.4902	>0.05
Male	186 (39.49)	181 (37.32)
Female	285 (60.51)	304 (62.68)
Age	59.41±8.14	57.47±8.22	−3.66	<0.05
BMI (kg/m2)	468	482	13.1033	<0.05
<18.5	28 (5.98)	9 (1.87)	8.0837	<0.05
[18.5, 24)	189 (40.38)	180 (37.34)	RG
[24, 28)	176 (37.61)	202 (41.91)	1.6218	>0.05
>28	75 (16.03)	91 (18.88)	1.6704	>0.05
Level of income	471	485	11.7690	<0.05
<12,000	367 (77.92)	350 (72.16)	RG
(12,000, 20,000)	65 (13.8)	60 (12.37)	0.0283	>0.05
>20,000	39 (8.28)	75 (15.46)	11.3430	<0.05
Level of education	471	485	11.3755	<0.05
Below primary school	140 (29.72)	108 (22.27)	RG
Primary school/Junior high school	305 (64.76)	329 (67.84)	4.9654	<0.05
High school and above	26 (5.52)	48 (9.9)	10.3690	<0.05
Smoking status	441	456	13.5708	<0.05
Smoking index*≤200	240 (54.42)	303 (66.45)
Smoking index>200	201 (45.58)	153 (33.55)
Second-hand smoking (never-smokers)	150	310	0.5807	>0.05
Yes	70 (46.67)	133 (52.90)
No	80 (53.33)	177 (57.10)
Indoor fuel use	450	471	18.5861	<0.05
No fuel/Natural gas/Electricity	18 (4.00)	55 (11.68)
Coal/Wood/Straw	432 (96.00)	416 (88.32)
Outdoor straw burning	449	470	10.7516	<0.05
Yes	336 (74.83)	305 (64.89)
No	113 (25.17)	165 (35.11)
History of RD	471	485	51.9267	<0.05
Yes	112 (23.78)	34 (7.01)
No	359 (76.22)	451 (92.99)
History of CHD/CHF	471	485	4.2892	<0.05
Yes	127 (29.96)	103 (21.24)
No	344 (73.04)	382 (78.76)
History of CVD	471	485	4.6860	<0.05
Yes	108 (22.93)	84 (17.32)
No	363 (77.07)	401 (82.68)
IgG	16.01±4.29	16.69±4.37	2.37	<0.05
IgA	2.22±1.03	2.31±0.93	2.0000	<0.05
IgM	1.17±0.58	1.12±0.57	0.1930	>0.05
C3	1.22±0.24	1.24±0.56	−1.1509	>0.05
C4	0.30±0.09	0.30±0.11	−0.51	>0.05
CRP	3.69±6.52	3.02±4.75	2.5667	<0.05

Notes: Continuous variables are expressed as mean and standard deviation, while categorical variables are presented as the number of patients in each group and percentage in the study group with respect to the total population. *Smoking index = the number of cigarettes smoked per day × the number of years of smoking.

Abbreviations: BMI, body mass index; RG, reference group; RD, respiratory disease; CHD/CHF, coronary heart disease and congestive heart failure; CVD, cerebrovascular disease; IgG, Immunoglobulin G; IgM, Immunoglobulin M; IgA, Immunoglobulin A; C3, the third complement component; C4, the fourth complement component; CRP, C-reactive protein.

Table 2 Univariate Logistic Nonlinear Regression Model to Analyze the Effects of IgM, C3, C4 on Chronic Obstructive Pulmonary Disease

Characteristics	β	SE (β)	Wald Chi-Square Value	P-value
IgM	0.2969	0.3051	0.9474	0.3304
IgM2	−0.0477	0.0906	0.2777	0.5982
C3	3.5619	1.8539	3.6913	0.0547
C32	−1.5399	0.7252	4.5093	0.0337
C4	0.4791	0.4112	1.3577	0.2439
C42	−1.4583	0.9776	2.2255	0.1357

Abbreviations: IgM, Immunoglobulin M; C3, the third complement component; C4, the fourth complement component.

Table 3 Multivariate Gradual Logistic Regression Analysis for Risk Factors of Chronic Obstructive Pulmonary Disease

Characteristics	β	SE (β)	OR (95% CI)	P-value
RD	1.5301	0.2331	4.619 (2.925–7.293)	0.0003
Smoking status	0.3976	0.1541	1.488 (1.100–2.013)	<0.0001
Indoor fuel use	0.8545	0.3127	2.350 (1.273–4.338)	0.0099
Straw burning outdoor	0.4244	0.1668	1.529 (1.103–2.120)	0.0063
CRP	0.3783	0.1341	1.460 (1.122–1.899)	0.0109
C3	5.7883	2.1593	326.442 (4.741–>999.999)	0.0048
C3^2	−2.5193	0.8505	0.081 (0.015–0.426)	0.0073

Abbreviations: RD, respiratory disease; C3, the third complement component; CRP, C-reactive protein.

Table 4 Results of the Principal Component Analysis

Principal Component	Eigenvalue	Difference	Proportion	Cumulative
PRIN 1	2.65861343	0.71186102	0.1772	0.1772
PRIN 2	1.94675241	0.59745936	0.1298	0.3070
PRIN 3	1.34929305	0.17051207	0.0900	0.3970
PRIN 4	1.17878098	0.08205982	0.0786	0.4756
PRIN 5	1.09672117	0.09870783	0.0731	0.5487
PRIN 6	0.99801334	0.07258332	0.0665	0.6152
PRIN 7	0.92543002	0.07846652	0.0617	0.6769
PRIN 8	0.84696350	0.05007724	0.0565	0.7334
PRIN 9	0.79688626	0.05579577	0.0531	0.7865
PRIN 10	0.74109050	0.02792364	0.0494	0.8359
PRIN 11	0.71316686	0.05375892	0.0475	0.8834
PRIN 12	0.65940794	0.08171214	0.0440	0.9274
PRIN 13	0.57769580	0.07713305	0.0385	0.9659
PRIN 14	0.50056275	0.48994074	0.0334	0.9993
PRIN 15	0.01062200		0.0007	1.0000

Table 5 Multivariate Gradual Logistic Regression Analysis for Principal Components of Chronic Obstructive Pulmonary Disease

Principal Component	β	SE (β)	Wald Chi-Square Value	P-value
Intercept	−0.0423	0.0731	0.3338	0.5634
PRIN 2	0.4343	0.0579	56.3579	<0.0001
PRIN 5	0.1468	0.0705	4.3315	0.0374
PRIN 6	0.2697	0.0749	12.9794	0.0003
PRIN 7	−0.243	0.0783	9.6322	0.0019
PRIN 8	0.2445	0.0807	9.1818	0.0024

Table 6 Results of Logistics Regression Analysis for Conversion of Principal Components into Primary Variables

The Primary Variable	β	SE (β)	U-value	P-value	OR (95% CI)
Age	0.0116	0.0031	3.7821	<0.05	1.0117(1.0056–1.0178)
BMI	−0.0195	0.0217	0.8974	>0.05	0.9807(0.9399–1.0233)
Level of education	−0.2532	0.0461	5.4954	<0.05	0.7763(0.7093–0.8497)
Level of income	0.0067	0.0367	0.1815	>0.05	1.0067(0.9368–1.0818)
Smoking status	0.3490	0.0517	6.7555	<0.05	1.4177(1.2811–1.5687)
Indoor fuel use	0.8367	0.0947	8.8379	<0.05	2.3088(1.9178–2.7796)
Outdoor straw burning	0.4935	0.0558	8.8407	<0.05	1.6381(1.4683–1.8275)
History of RD	1.2750	0.0693	18.4027	<0.05	3.5787(3.1243–4.0992)
History of CHD/CHF	0.2050	0.0588	3.4873	<0.05	1.2275(1.0939–1.3773)
History of CVD	0.1428	0.0637	2.2432	<0.05	1.1535(1.0182–1.3068)
IgG	−0.0085	0.0057	1.4759	>0.05	0.9916(0.9805–1.0028)
IgA	0.0789	0.0592	1.3328	>0.05	1.0821(0.9635–1.2153)
C3	0.0133	0.0995	0.1342	>0.05	1.0134(0.8339–1.2316)
C3^2	0.0059	0.0386	0.1521	>0.05	1.0059(0.9326–1.0849)
CRP	0.1815	0.0387	4.6893	<0.05	1.1990(1.1114–1.2935)

Abbreviations: BMI, body mass index; RD, respiratory disease; CHD/CHF, coronary heart disease and congestive heart failure; CVD, cerebrovascular disease; IgG, Immunoglobulin G; IgA, Immunoglobulin A; C3, the third complement component; CRP, C-reactive protein.