Paradoxical association between body mass index and in-hospital mortality in elderly patients with chronic obstructive pulmonary disease in Japan

Figures & data

Table 1 Characteristics and comorbidities in elderly patients with COPD

	Body mass index category (kg/m^2)					P-value
	Underweight (<18.5) (n=82,467)	Low–normal weight (18.5–22.9) (n=113,837)	High–normal weight (23.0–24.9) (n=35,152)	Overweight (25.0–29.9) (n=28,594)	Obesity (≥30) (n=3,890)
	n (%)	n (%)	n (%)	n (%)	n (%)
Age (years), mean [SD]	79.1 [7.3]	77.8 [7.2]	76.6 [6.8]	76.1 [6.6]	75.8 [6.5]	<0.001
65–74 years	23,226 (28.2)	39,269 (34.5)	14,045 (40.0)	12,252 (42.8)	1,689 (43.4)
75–84 years	39,210 (47.5)	53,822 (47.3)	16,526 (47.0)	13,144 (46.0)	1,814 (46.6)
85+ years	20,031 (24.3)	20,746 (18.2)	4,581 (13.0)	3,198 (11.2)	387 (9.9)
Sex						<0.001
Male	64,352 (78.0)	93,244 (81.9)	28,964 (82.4)	22,193 (77.6)	2,304 (59.2)
Female	18,115 (22.0)	20,593 (18.1)	6,188 (17.6)	6,401 (22.4)	1,586 (40.8)
Dyspnea grade						<0.001
I	5,631 (10.2)	13,210 (19.3)	5,090 (24.9)	4,108 (26.1)	424 (21.3)
II	6,586 (11.9)	11,480 (16.7)	3,730 (18.2)	2,889 (18.4)	330 (16.5)
III	6,751 (12.2)	9,757 (14.2)	2,982 (14.6)	2,281 (14.5)	257 (12.9)
IV	12,782 (23.0)	14,370 (21.0)	3,914 (19.1)	2,882 (18.3)	402 (20.2)
V	15,047 (27.1)	12,872 (18.8)	3,074 (15.0)	2,286 (14.6)	402 (20.2)
Unspecified	8,666 (15.6)	6,858 (10.0)	1,652 (8.1)	1,265 (8.1)	180 (9.0)
Disability of ADL						<0.001
20	26,820 (38.1)	57,248 (56.9)	20,668 (65.4)	17,143 (66.5)	1,976 (58.0)
15–19	7,860 (11.2)	10,601 (10.5)	3,007 (9.5)	2,458 (9.5)	416 (12.2)
14–10	9,849 (14.0)	10,808 (10.7)	2,867 (9.1)	2,204 (8.6)	360 (10.6)
9–5	6,646 (9.4)	6,472 (6.4)	1,612 (5.1)	1,313 (5.1)	202 (5.9)
0–4	19,237 (27.3)	15,477 (15.4)	3,441 (10.9)	2,648 (10.3)	454 (13.3)
Level of consciousness						<0.001
Alert	69,718 (86.1)	102,942 (91.3)	32,693 (93.7)	26,734 (94.0)	3,587 (92.7)
Dull	7,950 (9.8)	7,250 (6.4)	1,649 (4.7)	1,274 (4.5)	206 (5.3)
Somnolence	1,989 (2.5)	1,426 (1.3)	304 (0.9)	234 (0.8)	48 (1.2)
Coma	1,330 (1.6)	1,077 (1.0)	255 (0.7)	191 (0.7)	27 (0.7)
Type of hospital admission						<0.001
Scheduled	32,521 (39.4)	59,478 (52.2)	20,940 (59.6)	17,542 (61.3)	2,226 (57.2)
Emergency	49,946 (60.6)	54,359 (47.8)	14,212 (40.4)	11,052 (38.7)	1,664 (42.8)
Comorbidities
Asthma	10,827 (13.1)	16,294 (14.3)	5,263 (15.0)	4,341 (15.2)	771 (19.8)	<0.001
Pneumonia	22,637 (27.4)	23,753 (20.9)	6,089 (17.3)	4,262 (14.9)	517 (13.3)	<0.001
Aspiration pneumonia	7,755 (9.4)	4,884 (4.3)	924 (2.6)	569 (2.0)	69 (1.8)	<0.001
Interstitial pneumonitis	3,285 (4.0)	6,419 (5.6)	2,509 (7.1)	1,981 (6.9)	206 (5.3)	<0.001
Respiratory failure	23,995 (29.1)	22,822 (20.0)	5,692 (16.2)	4,314 (15.1)	702 (18.0)	<0.001
Lung cancer	12,231 (14.8)	25,733 (22.6)	9,128 (26.0)	7,098 (24.8)	621 (16.0)	<0.001
Heart failure	13,935 (16.9)	17,327 (15.2)	4,881(13.9)	4,261 (14.9)	821 (21.1)	0.001
Ischemic heart disease	6,766 (8.2)	12,524 (11.0)	4,656 (13.2)	4,339 (15.2)	559 (14.4)	<0.001
Pulmonary embolism	250 (0.3)	406 (0.4)	147 (0.4)	154 (0.5)	46 (1.2)	0.049
Cardiac arrhythmia	5,120 (6.2)	8,122 (7.1)	2,567 (7.3)	2,240 (7.8)	323 (8.3)	0.144
Cerebrovascular disease	6,452 (7.8)	8,933 (7.8)	2,609 (7.4)	2,148 (7.5)	275 (7.1)	0.448
Liver disease	1,279 (1.6)	2,055 (1.8)	703 (2.0)	621 (2.2)	107 (2.8)	<0.001
Chronic renal failure	1,986 (2.4)	3,382 (3.0)	938 (2.7)	779 (2.7)	148 (3.8)	<0.001
Anxiety/depression	1,378 (1.7)	1,762 (1.5)	542 (1.5)	455 (1.6)	79 (2.0)	0.041
Bone fracture	3,473 (4.2)	3,605 (3.2)	865 (2.5)	642 (2.2)	87 (2.2)	0.011

Note: Data were expressed as number (%) or mean[SD].

Abbreviations: ADL, activities of daily life; COPD, chronic obstructive pulmonary disease; SD, standard deviation.

Figure 1 All-cause in-hospital mortality among elderly patients with COPD according to body mass index category.

Abbreviation: COPD, chronic obstructive pulmonary disease.

Table 2 Multivariable logistic regression analysis for all-cause in-hospital mortality

	Adjusted odds ratio	95% confidence interval	P-value
Body mass index (kg/m^2)
<18.5	1.55	1.48–1.63	<0.001
18.5–22.9	Reference
23–24.9	0.76	0.70–0.82	<0.001
25–29.9	0.73	0.66–0.80	<0.001
≥30	0.67	0.52–0.86	<0.002
Age
65–74 years	Reference
75–84 years	1.17	1.11–1.24	<0.001
85+ years	1.33	1.24–1.41	<0.001
Sex
Male	Reference
Female	0.61	0.57–0.65	<0.001
Dyspnea grade
I	Reference
II	1.72	1.48–2.01	<0.001
III	2.58	2.19–3.03	<0.001
IV	3.96	3.36–4.68	<0.001
V	10.78	9.03–12.86	<0.001
Unspecified	10.06	8.33–12.15	<0.001
Disability of ADL
20	Reference
19–15	1.49	1.35–1.64	<0.001
14–10	2.00	1.83–2.18	<0.001
9–5	2.71	2.45–3.00	<0.001
4–0	4.32	3.91–4.76	<0.001
Consciousness level
Alert	Reference
Dull	1.21	1.12–1.30	<0.001
Somnolence	1.53	1.37–1.71	<0.001
Coma	2.87	2.53–3.26	<0.001
Emergency admission	1.43	1.33–1.54	<0.001
Asthma	0.57	0.53–0.61	<0.001
Pneumonia	1.08	1.02–1.14	0.005
Aspiration pneumonia	1.18	1.09–1.28	<0.001
Interstitial pneumonitis	2.28	2.12–2.45	<0.001
Respiratory failure	1.15	1.09–1.22	<0.001
Lung cancer	3.89	3.63–4.17	<0.001
Heart failure	1.21	1.14–1.28	<0.001
Ischemic heart disease	0.87	0.80–0.95	<0.001
Pulmonary embolism	1.25	0.89–1.74	0.192
Cardiac arrhythmia	1.07	0.99–1.17	0.106
Cerebrovascular disease	0.83	0.76–0.91	<0.001
Liver disease	1.30	1.08–1.56	0.005
Chronic renal failure	1.64	1.44–1.87	<0.001
Anxiety/depression	1.033	0.87–1.23	0.721
Bone fracture	1.41	1.20–1.65	<0.001

Abbreviation: ADL, activities of daily life.

Table S1 Patient’s clinical characteristics

	Mean	SD	Patients number (n) (total n=263,940)	Prevalence (%)
Age (years)	77.8	7.2
Sex
Male			211,057	80.0
Female			52,883	20.0
BMI (kg/m^2)	20.6	3.9
Smoking
Pack-year	55.6	35.6
Dyspnea grade by Hugh-Jones classification†
I			28,463	17.6
II			25,015	15.4
III			22,028	13.6
IV			34,350	21.2
V			33,681	20.8
Unspecified			18,621	11.5
Level of consciousness by Japan coma scale†
Alert			235,674	90.3
Dull			18,329	7.0
Somnolence			4,001	1.5
Coma			2,880	1.1
Disability of ADL by Barthel Index†
20			123,855	53.4
15–19			24,342	10.5
10–14			26,088	11.3
5–9			16,245	7.0
0			41,257	17.8
Style of hospital admission
Scheduled			132,707	50.3
Emergency			131,233	49.7
Primary diagnosis at admission
Respiratory disease			107,778	40.8
COPD			23,447	8.9
Acute exacerbation			4,207	1.6
Viral infection			765	0.3
Asthma			5,067	1.9
Pneumonia			37,283	14.1
Aspiration pneumonia			9,521	3.6
Interstitial pneumonia			4,590	1.7
Respiratory failure			13,302	5
Others			9,596	3.7
Lung cancer			40,566	15.4
Cardiac disease			20,295	7.7
Heart failure			9,986	3.8
Ischemic heart disease			5,862	2.2
Pulmonary embolism			295	0.1
Cardiac arrhythmia			1,149	0.4
Others			3,003	1.2
Cerebrovascular disease			1,603	0.6
Liver disease			628	0.2
Chronic renal failure			985	0.4
Bone fracture			6,502	2.5
Others			85,583	32.4
During hospitalization
ICU admission			14,683	6.2
Mechanical ventilation			20,615	7.8
Death‡			7,188	34.9

Notes: Prevalence was expressed by percentage of total patients, unless otherwise indicated.

† Prevalence was expressed as percentage of each factor among number of patients in each factor.

‡ Prevalence was expressed as percentage of deaths among the number of patients who underwent mechanical ventilation.

Abbreviations: ADL, activities of daily life; BMI, body mass index; COPD, chronic obstructive pulmonary disease; ICU, intensive care unit; SD, standard deviation.