Association of Body Mass Index and Abdominal Obesity with the Risk of Airflow Obstruction: National Health and Nutrition Examination Survey (NHANES) 2007–2012

Figures & data

Figure 1. Flow chart of the screening process for the selection of eligible participants.

Table 1. Characteristics of participants by airflow obstruction, NHANES 2007–2012, adults ≥20 years and ≤80 years of age.

	Fixed ratio				LLN
	Non-airflow obstruction	Airflow obstruction	P-value		Non-airflow obstruction	Airflow obstruction	P-value
Number of participants (%)	11,115 (86.4)	1750 (13.6)			11,504 (89.4)	1361 (10.6)
Age group (years, %)			<0.01				<0.01
220–39	4529 (40.7)	212 (12.1)			2345 (41.9)	107 (12.0)
40–59	4074 (36.7)	581 (33.2)			2024 (36.0)	283 (31.9)
≥60	2512 (22.6)	957 (54.7)			1239 (22.1)	498 (56.1)
Sex (%)			<0.01				<0.01
Male	5389 (48.5)	1116 (63.8)			5617 (48.8)	888 (65.2)
Female	5726 (51.5)	634 (36.2)			5887 (51.2)	473 (34.8)
Race/Ethnicity (%)			<0.01				<0.01
Mexican American	1909 (17.2)	132 (7.5)			1954 (17.0)	87 (6.4)
Other-Hispantic	1274 (11.2)	120 (6.9)			1305 (11.3)	89 (6.5)
Non-Hispantic White	4488 (40.4)	1053 (60.2)			4710 (40.9)	831 (61.1)
Non-Hispantic Black	2424 (21.8)	348 (19.9)			2490 (21.6)	282 (20.7)
Other race	1020 (9.2)	97 (5.5)			1045 (9.1)	72 (5.3)
Level of education (%)			<0.01				<0.01
<High school	1671 (16.7)	320 (20.5)			1738 (16.8)	253 (20.9)
High school	2478 (24.8)	452 (29.1)			2559 (24.7)	372 (30.7)
>High school	5867 (58.5)	787 (50.4)			6066 (58.5)	588 (48.5)
Marital status (%)			0.432				0.496
Married/Living with partner	958 (17.7)	124 (16.5)			983 (17.6)	99 (16.5)
Widowed/Divorced/ Separated/Never married	4462 (82.3)	627 (83.5)			4589 (82.4)	500 (83.5)
Household income (%)			<0.01				<0.01
Under $20,000	2051 (19.3)	408 (24.2)			2134 (19.3)	325 (24.8)
$20,000 and over	8601 (87.0)	1280 (75.8)			8896 (80.7)	986 (75.2)
Body mass index (kg/m^2, %)			<0.01				<0.01
<18.5	138 (1.2)	42 (2.5)			147 (1.3)	34 (2.5)
18.5 to <25 kg/m^2	3029 (27.3)	585 (33.4)			3167 (27.5)	447 (32.8)
25 to <30 kg/m^2	3713 (33.4)	624 (35.7)			3841 (33.4)	496 (36.4)
≥30 kg/m^2	4235 (38.1)	498 (28.5)			4349 (37.8)	384 (28.2)
Work physical activity (%)			0.081				0.054
Vigorous activity	2175 (19.6)	377 (21.6)			2255 (19.6)	297 (21.8)
Moderate activity	2781 (22.3)	401 (22.9)			2565 (22.3)	317 (23.3)
Other	6459 (58.1)	971 (55.5)			6684 (58.1)	746 (54.9)
Recreational physical activity (%)			<0.01				<0.01
Vigorous activity	2707 (24.4)	244 (13.9)			2775 (24.1)	176 (12.9)
Moderate activity	2949 (26.5)	488 (27.9)			3082 (26.8)	355 (26.1)
Other	5458 (49.1)	1018 (58.2)			5646 (49.1)	830 (61.0)
Abdominal obesity	6110 (55.0)	925 (52.9)	0.099		6298 (54.7)	737 (54.2)	0.743
Smoking at least 100 cigarettes (%)	4614 (41.5)	1240 (70.9)	<0.01		4836 (42.0)	1018 (74.8)	<0.01
Diabetes (%)	1102 (9.9)	274 (14.1)	<0.01		1153 (10.0)	196 (14.4)	<0.01
Hypertension (%)	3274 (29.5)	778 (44.5)	<0.01		3424 (29.8)	628 (46.1)	<0.01
Respiratory illness (%)	1980 (18.4)	447 (26.6)	<0.01		2053(18.5)	374 (28.7)	<0.01

LLN, lower limit of normal.

Table 2. Weighted odds ratios (95% confidence intervals) of airflow obstruction across body mass index and smoking, NHANES 2007–2012 (N = 12,865).

		Case/Participants	Crude	Model 1^a	Model 2^b
Fixed ratio	BMI (kg/m^2)
	<18.5	43/181	1.61 (1.13–2.30)	1.91 (1.30–2.82)	1.97 (1.13–3.44)
	18.5 to <25	585/3614	1.00 (Ref.)	1.00 (Ref.)	1.00 (Ref.)
	25 to <30	624/4337	0.87 (0.77–0.98)	0.63 (0.56–0.72)	0.54 (0.43–0.68)
	≥30	498/4733	0.61 (0.54–0.69)	0.46 (0.40–0.53)	0.47 (0.37–0.60)
	Smoking
	No	510/7011	1.00 (Ref.)	1.00 (Ref.)	1.00 (Ref.)
	Yes	1240/5854	3.41 (3.05–3.81)	2.90 (2.58–3.25)	2.81 (2.28–3.46)
LLN	BMI (kg/m^2)
	<18.5	34/181	1.63 (1.11–2.41)	1.98 (1.30–3.02)	1.97 (1.08–3.60)
	18.5 to <25	447/3614	1.00 (Ref.)	1.00 (Ref.)	1.00 (Ref.)
	25 to <30	496/4337	0.91 (0.79–1.04)	0.67 (0.58–0.77)	0.48 (0.35–0.65)
	≥30	384/4733	0.62 (0.54–0.72)	0.47 (0.41–0.55)	0.38 (0.26–0.55)
	Smoking
	No	343/7011	1.00 (Ref.)	1.00 (Ref.)	1.00 (Ref.)
	Yes	1018/5854	5.48 (4.50–6.68)	4.54 (3.71–5.56)	3.25 (2.36–4.47)

BMI, body mass index; LLN, lower limit of normal.

a Adjusted for age and sex.

b Adjusted for age, sex, race, educational level, income, marital, recreational activity, work activity, hypertension, diabetes, and respiratory illness.

Table 3. Weighted odds ratios (95% confidence intervals) of airflow obstruction across body mass index, stratified by sex and smoking, NHANES 2007–2012 (N = 12,865).

	BMI (kg/m^2)	Sex		Smoking
		Male	Female	Yes	No
Fixed ratio	<18.5	1.09 (0.42–1.81)	2.46 (1.25–4.86)	2.13 (1.13–4.00)	1.65 (0.53–5.09)
	18.5 to <25	1.00 (Ref.)	1.00 (Ref.)	1.00 (Ref.)	1.00 (Ref.)
	25 to <30	0.65 (0.48–0.89)	0.37 (0.26–0.54)	0.55 (0.41–0.71)	0.49 (0.31–0.76)
	≥30	0.57 (0.41–0.79)	0.34 (0.24–0.48)	0.50 (0.38–0.66)	0.39 (0.25–0.61)
LLN	<18.5	2.36 (0.79–7.03)	1.58 (0.63–3.96)	2.12 (0.97–4.62)	1.27 (0.28–5.62)
	18.5 to <25	1.00 (Ref.)	1.00 (Ref.)	1.00 (Ref.)	1.00 (Ref.)
	25 to <30	0.53 (0.28–1.00)	0.39 (0.20–0.77)	0.55 (0.24–0.87)	0.57 (0.26–1.29)
	≥30	0.56 (0.29–1.10)	0.35 (0.18–0.68)	0.50 (0.30–0.85)	0.79 (0.32–1.96)

Adjusted for age and sex, race, educational level, income, marital, recreational activity, work activity, hypertension, diabetes, and respiratory illness.

BMI, body mass index; LLN, lower limit of normal.

Table 4. Weighted odds ratios (95% confidence intervals) of airflow obstruction across abdominal obesity and body mass index, NHANES 2007–2012 (N = 12,865).

Abdominal obesity	BMI (kg/m^2)	N	Fixed ratio	LLN
No	18.5 to <25	3338	1.00 (Ref.)	1.00 (Ref.)
	<18.5	181	2.06 (1.18–3.60)	2.01 (1.09–3.67)
	25 to <30	2138	0.49 (0.35–0.67)	0.50 (0.35–0.71)
	≥30	173	0.61 (0.23–1.61)	0.47 (0.14–1.59)
Yes	18.5 to <25	276	1.42 (0.84–2.40)	1.58 (0.90–2.77)
	25 to <30	2199	0.62 (0.46–0.83)	0.66 (0.48–0.91)
	≥30	4560	0.49 (0.37–0.63)	0.53 (0.40–0.70)

Adjusted for age and sex, race, educational level, income, marital, recreational activity, work activity, hypertension, smoking status, diabetes, and respiratory illness.

LLN, lower limit of normal.

Table 5. Weighted odds ratios (95% confidence intervals) of airflow obstruction across abdominal obesity and stratified by sex and smoking, NHANES 2007–2012 (N = 12,865).

			Fixed ratio	LLN
Total		Non-abdominal obesity	1.00 (Ref.)	1.00 (Ref.)
		Abdominal obesity	1.41(1.04–1.90)	1.38(0.98–1.93)
Sex	Male	Non-abdominal obesity	1.00 (Ref.)	1.00 (Ref.)
		Abdominal obesity	1.81 (1.21–2.74)	1.28 (0.72–2.28)
	Female	Non-abdominal obesity	1.00 (Ref.)	1.00 (Ref.)
		Abdominal obesity	1.16 (0.72–1.86)	1.09 (0.68–1.74)
Smoking	Yes	Non-abdominal obesity	1.00 (Ref.)	1.00 (Ref.)
		Abdominal obesity	1.46 (1.03–2.08)	1.07 (0.71–1.62)
	No	Non-abdominal obesity	1.00 (Ref.)	1.00 (Ref.)
		Abdominal obesity	1.24 (0.71–2.17)	0.60 (0.23–1.51)

Adjusted for age, sex, race, educational level, income, marital, body mass index, recreational activity, work activity, hypertension, smoking status, diabetes, and respiratory illness.

OR, odd ratio; CI, confidence interval; LLN, lower limit of normal.

Table 6. Interaction effects between underweight and smoking.

Underweight	Smoking	N	Fixed ratio		LLN
			OR (95% CI)^a	Interaction indexes (95% CI)	OR (95% CI)^a	Interaction indexes (95% CI)
No	No	6929	1.00		1.00
No	Yes	5755	2.89 (1.95–4.28)	RERI = 3.916 (0.243,7.588)	3.41 (2.97–3.92)	RERI = 4.216 (0.074,8.359)
Yes	No	82	1.44 (0.60–3.43)	Ap = 0.540 (0.231,0.848)	1.49 (0.53–4.23)	Ap = 0.518 (0.222,0.815)
Yes	Yes	99	2.67 (1.10–6.46)	SI = 2.673 (1.106,6.460)	8.13 (5.01–13.19)	SI = 2.445 (1.144,5.226)
Male
No	No	2991	1.00		1.00
No	Yes	3449	2.66 (1.65–4.31)	RERI = 0.359(−3.497,4.215)	3.33 (2.79–3.96)	RERI= −0.279 (−5.761,5.204)
Yes	No	20	1.74 (0.37–8.05)	Ap = 0.095 (−0.889,1.079)	2.83 (0.61–13.14)	AP= −0.057 (−1.202,1.088)
Yes	Yes	45	3.76 (1.91–7.42)	SI = 1.149 (0.252,5.243)	4.88 (2.41–9.88)	SI = 0.933(0.242,3.603)
Female
No	No	3938	1.00		1.00
No	Yes	2306	3.23 (2.71–3.85)	RERI = 8.552(1.187,15.918)	3.53 (2.87–4.33)	RERI = 8.914 (0.872,16.956)
Yes	No	62	1.25 (0.43–3.61)	Ap = 0.711 (0.506,0.915)	0.95 (0.22–4.07)	Ap = 0.719 (0.508,0.929)
Yes	Yes	54	12.04 (6.51–22.23)	SI = 4.442 (1.903,10.367)	12.10 (6.45–23.83)	SI = 4.581 (1.872,11.207)

AP, the attributable proportion due to interaction; CI, confidence interval; OR, odd ratio; RERI, relative excess risk due to interaction; SI, the synergy index; LLN, lower limit of normal.

a Adjusted for age, sex, and waist circumference.

Table 7. Interaction effects between abdominal obesity and smoking.

Abdominal obesity	Smoking	N	Fixed ratio		LLN
			OR (95% CI)^a	Interaction indexes (95% CI)	OR (95% CI)^a	Interaction indexes (95% CI)
No	No	3172	1.00		1.00
No	Yes	2658	2.97 (2.52–3.50)	RERI = 0.217 (−0.255,0.689)	3.43 (2.82–4.17)	RERI = 1.059 (0.276,1.841)
Yes	No	3839	0.91 (0.74–1.13)	Ap = 0.070 (−0.077,0.217)	1.48 (1.14–1.93)	Ap = 0.213 (0.079,0.347)
Yes	Yes	3196	3.11 (2.55–3.78)	SI = 1.115 (0.878,1.416)	4.97 (3.94–6.27)	SI = 1.363 (1.091,1.703)
Male
No	No	1782	1.00		1.00
No	Yes	1965	2.53 (2.06–3.11)	RERI = 0.804 (0.087,1.521)	4.54 (3.44–5.99)	RERI= −0.129(−10.850,10.591)
Yes	No	1229	1.39 (1.03–1.88)	Ap = 0.251 (0.049,0.382)	4.22 (0.52–34.28)	AP= −0.017 (−1.427,1.393)
Yes	Yes	1529	3.73 (2.89–4.81)	SI = 1.417 (1.038,1.934)	7.64 (3.28–17.80)	SI = 0.981 (0.200,4.823)
Female
No	No	1390	1.00		1.00
No	Yes	693	3.37 (2.50–4.53)	RERI = 0.101 (−0.894,1.095)	4.34 (3.04–6.20)	RERI = 0.027 (−1.238,1.778)
Yes	No	2610	1.07 (0.76–1.51)	Ap = 0.028 (−0.249,0.350)	1.55 (1.03–2.34)	AP= −0.052 (−0.232,0.336)
Yes	Yes	1667	3.54 (2.55–4.92)	SI = 1.041 (0.698,1.533)	5.17 (3.49–7.65)	SI = 1.069(0.735,1.555)

AP, the attributable proportion due to interaction; CI, confidence interval; OR, odd ratio; RERI, relative excess risk due to interaction; SI, the synergy index; LLN, lower limit of normal.

a Adjusted for age, sex, and body mass index.

Figure 2. Dose-response relationship between BMI and the ORs of airflow obstruction (FR). The solid line and dashed line represent the estimated ORs and their 95% confidence intervals. BMI, body mass index; FR, fixed ratio; LLN, lower limit of normal; OR, odds ratio.

Figure 3. Dose-response relationship between BMI and the ORs of airflow obstruction (LLN). The solid line and dashed line represent the estimated ORs and their 95% confidence intervals. BMI, body mass index; FR, fixed ratio; LLN, lower limit of normal; OR, odds ratio.