Effects of biomass smoke on pulmonary functions: a case control study

Figures & data

Table 1 Demographic properties of the females eliminated from the study

	n	%
Smokers (current/former)	176	49
Pneumonia, upper respiratory tract infection	65	18
Allergic asthma/rhinitis	55	15
Cardiovascular disease	35	10
Chronic renal failure	28	8
Total	359	100

Figure 1 People are exposed to heavy smoke due to the cooking conditions (lack of chimney and poor ventilation).

Figure 2 Dry animal dung (manure), rather than wood or charcoal, is used as the fuel source.

Table 2 PFT values of the study group and the control group

	Study group		Control group		P-value
	Median	IQR	Median	IQR
Age (years)	33.4	30–37	32.6	22.5–44.5	0.110
BMI (kg/m^2)	24.7	18–31	24.5	17–32	0.115
FEV1 (%)	78.0	71–82	80.0	76–87.5	0.023
FVC (%)	81.0	82–88	84.0	79–89	0.036
FEV1/FVC (%)	79.0	74–84	84.0	80.5–86	0.001
FEF 25–75 (%)	70.0	65–75	77.0	72–79	0.001

Note: Bold indicates a P-value <0.05.

Abbreviations: PFT, pulmonary function test; IQR, interquartile range; BMI, body mass index; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; FEF 25–75, forced expiratory flow during the 25%–75% portion of the FVC.

Figure 3 The difference of FEF 25–75 (A), FEV₁/FVC (B), FEV₁ (C), and FVC (D) results between the study group and control group.

Abbreviations: FEF 25–75, forced expiratory flow during the 25%–75% portion of the FVC; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity.

Table 3 Pathologic PFT results in the study group and control group

	Study group, n (%)	Control group, n (%)	P-value
Small airway disease (FEF 25–75 <60[%])	27 (23.4)	4 (5.5)	0.038
Obstruction (FEV1/FVC <70[%])	22 (19.1)	10 (13.0)	0.223
Restriction (FEV1/FVC >70[%],FVC < 80[%])	20 (17.3)	10 (13.0)	0.189

Note: Bold indicates a P-value <0.05.

Abbreviations: PFT, pulmonary function test; FEF 25–75, forced expiratory flow during the 25%–75% portion of the FVC; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity.

Table 4 Median values of the evaluated parameters in the study group (N=115)

	Median	Min	Max
Age (years)	33.030	18	48
Starting age (years)	18.300	15	22
Hours per day	2.920	2	4
Weeks per month	2.500	1	4
Duration (years)	14.550	2	28

Abbreviations: Min, minimum; Max, maximum.

Table 5 Determination of the risk factors for the altered PFT results

	Mean	SD	Mean	SD	P-value
	FEF 25–75 >60 (n=98)		FEF 25–75 ≤60 (n=17)
Starting age (years)	18.480	1.851	17.290	1.724	0.015
Hours per day	2.880	0.579	3.180	0.636	0.060
Weeks per month	2.410	0.848	3.060	1.029	0.008
Duration (years)	13.400	4.854	21.180	2.811	0.001
	FEV1/FVC >70 (n=93)		FEV1/FVC ≤70 (n=22)
Starting age (years)	18.510	1.851	17.450	1.765	0.018
Hours per day	2.900	0.572	3.000	0.690	0.522
Weeks per month	2.390	0.847	3.000	0.976	0.003
Duration (years)	13.120	4.750	20.590	3.232	0.001
	FEV1/FVC >70, FVC >80% (n=95)		FEV1/FVC >70, FVC <80% (n=20)
Starting age (years)	18.400	1.874	17.300	1.636	0.048
Hours per day	2.880	0.583	3.400	0.516	0.009
Weeks per month	2.420	0.852	3.400	0.966	0.001
Duration (years)	13.780	4.901	22.600	2.989	0.001

Note: Bold indicates a P-value <0.05.

Abbreviations: PFT, pulmonary function test; SD, standard deviation; FEF 25–75, forced expiratory flow during the 25%–75% portion of the FVC; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity.

Table 6 Correlation analysis between PFT results and independent variables in the study group

	Starting age	Hours per day	Weeks per month	Duration (years)
FEV1/FVC (%)
r	0.067	−0.106	−0.074	−0.488
P	0.480	0.261	0.429	0.001
FEV1 (%)
r	0.270	−0.172	−0.194	−0.749
P	0.004	0.067	0.038	0.001
FVC (%)
r	0.148	−0.236	−0.200	−0.522
P	0.114	0.011	0.032	0.001

Note: Bold indicates a P-value <0.05.

Abbreviations: PFT, pulmonary function test; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity.

Figure 4 ROC curves of duration with small, obstructive, and restrictive airway diseases.

Notes: (A) ROC curve analysis for small airway disease (sensitivity, 100%; specificity, 76.9%). (B) ROC curve analysis for obstructive lung disease (sensitivity, 95.5%; specificity, 69.9%). (C) ROC curve analysis for restrictive lung disease (sensitivity, 100%; specificity, 74.3%).
Abbreviation: ROC, receiver operating characteristic.

Table 7 Median values of CEI among biomass exposed women, who had altered and normal PFT results

	n	Mean ± SD	P-value
Small airway disease			0.001
FEF 25–75 >60 (%)	98	30.5±19.6
FEF 25–75 <60 (%)	27	65.5±35.2
Obstruction			0.001
FEV1/FVC >70 (%)	93	31.4±20.6
FEV1/FVC <70 (%)	22	71.0±34.6
Restriction			0.001
FVC >80 (%)	95	32.4±21.2
FVC <80 (%)	20	87.6±30.9

Abbreviations: CEI, cumulative exposure index; PFT, pulmonary function test; SD, standard deviation; FEF 25–75, forced expiratory flow during the 25%–75% portion of the FVC; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity.

Table 8 Cutoff values of CEI for small airway disease, obstruction, and restriction

CEI	AUC	95% CI	P-value	Cutoff	Sensitivity (%)	Specificity (%)
Small airway disease	0.876	0.802–0.930	<0.001	34.7	94.1	71.4
Obstruction	0.828	0.747–0.892	<0.001	42.7	63.6	86.0
Restriction	0.930	0.867–0.969	<0.001	45.3	90.0	84.8

Abbreviations: CEI, cumulative exposure index; AUC, area under the curve; CI, confidence interval.

Figure 5 The difference of median values of CEI among all biomass exposed women based on PFT results.

Notes: The difference of CEI among all biomass exposed women with and without (A) small airway disease; (B) obstruction; and (C) restriction. Circles and stars indicate the cases out of 95% CI.

Abbreviation: CEI, cumulative exposure index.

Figure 6 ROC curve analysis of CEI for small airway disease and obstructive and restrictive pulmonary diseases.

Abbreviations: ROC, receiver operating characteristic; CEI, cumulative exposure index.