Impact of BMI on exacerbation and medical care expenses in subjects with mild to moderate airflow obstruction

Figures & data

Table 1 Comparison of demographic and clinical characteristics among patients with chronic obstructive pulmonary disease (COPD) stratified by body mass index (BMI)*

	BMI (kg/m^2)				P-value
	<18.5	18.5–22.9	23–24.9	≥25
Subjects	37 (2.8)	562 (42.6)	354 (26.8)	367 (27.8)
Age, years	70.5 ± 8.3	65.5 ± 9.2	64.5 ± 9.5	62.4 ± 9.6	<0.01
Sex, male (%)	33 (89.2)	529 (95.9)	344 (97.2)	356 (97.0)	0.08
BMI (kg/m^2)	17.5 ± 0.8	21.4 ± 1.1	23.9 ± 0.6	26.8 ± 1.5	<0.01
Smoking, pack-year	33.5 ± 15.6	35.3 ± 21.0	35.1 ± 21.4	35.6 ± 20.9	0.94
Comorbid condition
DM	11 (29.7)	205 (36.5)	133 (37.6)	148 (40.3)	0.49
HTN	22 (59.5)	274 (48.8)	196 (55.4)	234 (63.8)	<0.01
Ischemic heart disease	5 (13.5)	49 (8.7)	39 (11.0)	39 (10.6)	0.55
Congestive heart failure	3 (8.1)	29 (5.2)	13 (3.7)	16 (4.4)	0.54
Arthritis	5 (13.5)	54 (9.6)	34 (9.6)	38 (10.4)	0.87
Osteoporosis	11 (29.7)	72 (12.8)	46 (13.0)	32 (8.7)	<0.01
GERD	19 (51.4)	293 (52.1)	201 (56.8)	187 (51.0)	0.41
History of PTB	0 (0)	5 (0.9)	6 (1.7)	1 (0.3)	0.22
Depression	9 (24.3)	77 (13.7)	49 (13.8)	51 (13.9)	0.35
History of exacerbation in the past year
Moderate to severe	28 (75.7)	400 (71.2)	250 (70.6)	263 (71.7)	0.93
Frequency n/year	4.1 ± 5.5	3.4 ± 4.6	3.0 ± 4.0	3.4 ± 4.4	0.40
Initial treatment, n (%)
ICS and LABA	1 (2.7)	17 (3.0)	7 (2.0)	11 (3.0)	0.79
LAMA and/or LABA	1 (2.7)	4 (0.7)	3 (0.9)	0 (0)	0.15
SABA and/or SAMA	1 (2.7)	23 (4.1)	14 (4.0)	17 (4.6)	0.93

Note:

* Data are presented as number (%) or mean ± SD.

Abbreviations: BMI, body mass index; DM, diabetes mellitus; GERD, gastroesophageal reflux disease; HTN, hypertension; ICS, inhaled corticosteroid; LABA, long-acting beta₂ receptor agonist; LAMA, long-acting muscarinic receptor agonist; PTB, pulmonary tuberculosis; SABA, short-acting beta₂ receptor agonist; SAMA, short-acting muscarinic receptor agonist.

Figure 1 Flow diagram of the study participants.

Table 2 Comparison of the quality of life, laboratory findings, and pulmonary function among patients with chronic obstructive pulmonary disease (COPD)*

	BMI (kg/m^2)				P-value
	<18.5	18.5–22.9	23–24.9	≥25
Subjects	37 (2.8)	562 (42.6)	354 (26.8)	367 (27.8)
Index of quality of life
EQ-5D	0.86 ± 0.18	0.92 ± 0.12	0.93 ± 0.11	0.93 ± 0.13	<0.01
Laboratory test
Total serum cholesterol, mg/dL	167.3 ± 40.5	187.1 ± 36.1	187.6 ± 36.9	189.8 ± 35.1	<0.01
TG, mg/dL	126.5 ± 116.3	147.4 ± 120.9	167.2 ± 102.9	191.2 ± 181.9	<0.01
LDL cholesterol, mg/dL	109.5 ± 23.4	111.4 ± 36.5	109.8 ± 38.6	113.6 ± 32.0	0.93
HDL cholesterol, mg/dL	49.4 ± 12.2	46.8 ± 11.4	44.4 ± 11.0	42.6 ± 9.5	<0.01
Lung function
FVC, L	3.4 ± 0.7	3.9 ± 0.7	4.0 ± 0.8	3.9 ± 0.7	<0.01
FVC, % predicted	88.9 ± 15.0	92.5 ± 12.7	91.6 ± 13.0	87.4 ± 12.6	<0.01
FEV1, L	2.1 ± 0.5	2.4 ± 0.6	2.5 ± 0.6	2.5 ± 0.5	<0.01
FEV1, % predicted	76.0 ± 14.8	78.7 ± 12.9	79.6 ± 13.6	77.9 ± 12.0	0.18
FEV1/FVC	0.62 ± 0.07	0.63 ± 0.06	0.63 ± 0.06	0.65 ± 0.05	<0.01

Note:

* Data are presented as number (%) or mean ± SD.

Abbreviations: EQ-5D, EuroQol-5 Dimensions questionnaire; FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; HDL, high-density lipoprotein; LDL, low-density lipoprotein; TG, triglyceride; BMI, body mass index.

Table 3 Incidence of moderate to severe exacerbation during a 5-year period

Incidence rate of moderate to severe exacerbation
BMI (kg/m^2)	Crude IRR	95% CI	P-value	Adjusted IRRa	95% CI	P-value	Adjusted IRRb	95% CI	P-value
<18.5	1.10	0.80–1.51	0.57	0.94	0.69–1.29	0.72	0.95	0.70–1.30	0.75
18.5–22.9	Reference
23–24.9	0.94	0.82–1.06	0.32	0.96	0.85–1.09	0.52	0.96	0.85–1.09	0.53
≥25	0.88	0.77–0.99	0.04	0.97	0.86–1.10	0.68	0.98	0.86–1.11	0.70

Notes:

a Adjusted by age, sex, and FEV₁ (%).

b Adjusted by age, sex, smoking pack-year and FEV₁ (%).

Abbreviations: IRR, incidence rate ratio; BMI, body mass index.

Table 4 Cumulative chronic obstructive pulmonary disease (COPD)-related health-care utilization and medical expenses# during a 5-year period*

	BMI (kg/m^2)				P-value
	<18.5	18.5–22.9	23–24.9	≥25
Subjects	37 (2.8)	562 (42.6)	354 (26.8)	367 (27.8)
COPD-related health-care utilization and medical expenses
Hospitalization
Number per person-year	4.7 ± 9.6	1.1 ± 5.4	1.7 ± 6.8	0.8 ± 3.9	<0.01
Cost per person-year	846.5 ± 1,933.5	248.6 ± 1,575.5	283.2 ± 1,144.0	183.0 ± 956.5	0.04
Outpatient clinic visits
Number per person-year	3.6 ± 5.9	3.0 ± 3.7	2.7 ± 4.0	2.3 ± 2.9	0.04
Cost per person-year	61.9 ± 100.0	45.3 ± 84.5	53.3 ± 178.0	37.7 ± 62.8	0.24
Pharmacy use
Number per person-year	3.5 ± 5.9	2.9 ± 3.6	2.6 ± 3.9	2.3 ± 2.8	0.04
Cost per person-year	22.7 ± 47.0	19.7 ± 41.9	17.5 ± 27.5	19.9 ± 41.7	0.75

Notes:

# All costs are presented in US dollars (USD) with an exchange rate of 1 USD equal to 1,140 Korean won (exchange rate on May, 2017).

* Data are presented as number (%) or mean ± SD.

Abbreviation: BMI, body mass index.

Table 5 Risk of chronic obstructive pulmonary disease (COPD)-related health-care utilization during a 5-year period

BMI (kg/m^2) group	Crude IRR (95% CI)			Adjusted IRRa (95% CI)			Adjusted IRRb (95% CI)
	Hospitalization	Outpatient clinic visits	Pharmacy use	Hospitalization	Outpatient clinic visits	Pharmacy use	Hospitalization	Outpatient clinic visits	Pharmacy use
<18.5	4.65 (0.46–47.03)	1.22 (0.73–1.98)	1.19 (0.72–1.96)	4.93 (0.52–46.38)	0.83 (0.52–1.34)	0.82 (0.51–1.33)	7.12 (0.77–66.02)	0.82 (0.51–1.32)	0.90 (0.82–0.99)
18.5–22.9	Reference
23–24.9	1.17 (0.46–2.96)	0.89 (0.73–1.09)	0.87 (0.71–1.06)	1.02 (0.42–2.50)	0.95 (0.78–1.15)	0.93 (0.76–1.12)	1.26 (0.50–3.16)	0.95 (0.79–1.15)	0.92 (0.88–0.96)
≥25	0.70 (0.28–1.75)	0.73 (0.60–0.89)	0.73 (0.60–0.89)	0.79 (0.33–1.94)	0.87 (0.72–1.05)	0.87 (0.72–1.05)	1.02 (0.41–2.52)	0.87 (0.72–1.06)	0.82 (0.79–0.86)
P for trend	0.25	0.01	0.01	0.25	0.50	0.48	0.01	0.52	<0.01

Notes:

a Adjusted by age, sex, and FEV₁ (%).

b Adjusted by age, sex, smoking pack-year, and FEV₁ (%).

Abbreviations: IRR, incidence rate ratio; BMI, body mass index.

Figure S1 Cumulative chronic obstructive pulmonary disease (COPD)-related medical costs per person-year stratified by body mass index (BMI).

Note: Medical costs are presented in US dollars (USD) with an exchange rate of 1 USD equal to 1,140 Korean won (exchange rate on May, 2017).

Table S1 Subgroup analysis of the risk of exacerbation according to the severity of airflow limitation

IRR (95% CI)	BMI (kg/m^2) group				P-value
	<18.5	18.5–22.9	23–24.9	≥25
FEV1 ≥80% predicted
Crude IRR	1.01 (0.61–1.67)	Reference	0.90 (0.74–1.08)	0.88 (0.72–1.07)	0.51
Adjusted IRRa	0.88 (0.54–1.45)		0.89 (0.75–1.07)	0.98 (0.81–1.19)	0.65
Adjusted IRRb	0.89 (0.54–1.46)		0.90 (0.75–1.07)	0.98 (0.81–1.20)	0.66
50%≤ FEV1<80% predicted
Crude IRR	1.16 (0.77–1.74)	Reference	0.98 (0.82–1.17)	0.88 (0.74–1.04)	0.33
Adjusted IRRa	0.99 (0.67–1.47)		1.02 (0.86–1.22)	0.99 (0.84–1.16)	0.98
Adjusted IRRb	0.99 (0.67–1.47)		1.02 (0.86–1.21)	0.98 (0.84–1.16)	0.98

Notes:

a Adjusted by age, sex, and FEV₁ (%).

b Adjusted by age, sex, smoking pack-year, and FEV₁ (%).

Abbreviations: IRR, incidence rate ratio; FEV₁, forced expiratory volume in 1 s; BMI, body mass index.

Table S2 Subgroup analysis of the risk of chronic obstructive pulmonary disease (COPD)-related health-care utilization during a 5-year period according to the forced expiratory volume in 1 s (FEV₁)

IRR (95% CI)	BMI (kg/m^2)				P for trend
	<18.5	18.5–22.9	23–24.9	≥25
FEV1 ≥80% predicted
Crude IRR
Hospitalization	7.20 (0.20–265.07)	Reference	1.24 (0.33–4.66)	0.57 (0.14–2.32)	0.33
Outpatient clinic visits	0.52 (0.28–0.96)		1.04 (0.85–1.26)	0.89 (0.72–1.10)	0.11
Pharmacy use	0.33 (0.15–0.73)		1.04 (0.79–1.37)	0.90 (0.67–1.19)	0.08
Adjusted IRRa
Hospitalization	10.04 (0.29–348.56)		1.08 (0.30–3.92)	0.58 (0.14–2.38)	0.20
Outpatient clinic visits	0.45 (0.24–0.82)		1.05 (0.87–1.27)	0.97 (0.79–1.19)	0.05
Pharmacy use	0.27 (0.12–0.59)		1.05 (0.80–1.36)	1.00 (0.76–1.33)	0.03
Adjusted IRRb
Hospitalization	12.22 (0.37–402.38)		1.25 (0.34–4.58)	0.61 (0.15–2.40)	0.15
Outpatient clinic visits	0.45 (0.24–0.82)		1.05 (0.87–1.27)	0.97 (0.79–1.19)	0.05
Pharmacy use	0.28 (0.20–0.38)		1.08 (1.01–1.15)	0.99 (0.92–1.07)	<0.01
50%≤ FEV1<80% predicted
Crude IRR
Hospitalization	2.57 (0.15–42.62)	Reference	1.70 (0.50–5.77)	0.84 (0.27–2.63)	0.63
Outpatient clinic visits	1.58 (0.98–2.55)		0.86 (0.70–1.07)	0.73 (0.59–0.89)	<0.01
Pharmacy use	1.53 (0.79–2.96)		0.78 (0.59–1.04)	0.64 (0.49–0.84)	<0.01
Adjusted IRRa
Hospitalization	2.68 (0.18–40.95)		1.36 (0.41–4.48)	1.21 (0.39–3.73)	0.86
Outpatient clinic visits	1.22 (0.79–1.90)		0.89 (0.72–1.09)	0.86 (0.71–1.05)	0.25
Pharmacy use	1.14 (0.61–2.14)		0.83 (0.63–1.09)	0.78 (0.60–1.01)	0.22
Adjusted IRRb
Hospitalization	3.14 (0.21–46.92)		1.64 (0.49–5.54)	1.37 (0.44–4.21)	0.73
Outpatient clinic visits	1.21 (0.78–1.87)		0.86 (0.70–1.05)	0.85 (0.70–1.03)	0.16
Pharmacy use	1.11 (1.00–1.23)		0.79 (0.75–0.84)	0.73 (0.69–0.78)	<0.01

Notes:

a Adjusted by age, sex, and FEV₁ (%).

b Adjusted by age, sex, smoking pack-year, and FEV₁ (%).

Abbreviations: IRR, incidence rate ratio; BMI, body mass index; FEV₁, forced expiratory volume in 1 s.