The effect of BMI on COVID-19 outcomes among older patients in South Korea: a nationwide retrospective cohort study*

* An abstract of this work was presented at the 2020 Autumn Conference of The Korean Society of Emergency Medicine, December 10–12, 2020.

Figures & data

Figure 1. Flow chart of the study population. Definition of abbreviations: COVID-19: coronavirus disease 2019; BMI: body mass index

Table 1. Characteristics of study population by BMI group.

	Total (n = 1,272)	BMI (kg/m²)					p-Value
		<18.5 (n = 67)	18.5–22.9 (n = 488)	23.0–24.9 (n = 360)	25.0–29.9 (n = 326)	≥30 (n = 31)
Age (years)							<.001
60–69	684 (53.8)	17 (25.4)	251 (51.4)	207 (57.5)	190 (58.3)	19 (61.3)
70–79	378 (29.7)	28 (41.8)	136 (27.9)	111 (30.8)	95 (29.1)	8 (25.8)
≥80	210 (16.5)	22 (32.8)	101 (20.7)	42 (11.7)	41 (12.6)	4 (12.9)
Sex
Female	750 (59.0)	41 (61.2)	316 (64.8)	198 (55.0)	171 (52.5)	24 (77.4)	.001
Male	522 (41.0)	26 (38.8)	172 (35.2)	162 (45.0)	155 (47.5)	7 (22.6)
Outcome
Severe infection^† (N/A = 9)	136 (10.7)	15 (22.7)	52 (10.7)	23 (6.4)	41 (12.7)	5 (16.1)	.001
Death	117 (9.2)	15 (22.7)	46 (9.5)	18 (5.0)	35 (10.9)	3 (9.7)	<.001
ICU (N/A = 8)	106 (8.3)	6 (9.0)	33 (6.8)	27 (7.5)	35 (10.9)	5 (16.1)	.137
Vital sign
SBP (mmHg) (N/A = 1)							.001
<120	213 (16.7)	21 (31.3)	97 (19.9)	49 (13.6)	42 (12.9)	4 (12.9)
120–139	429 (33.7)	14 (20.9)	166 (34.1)	127 (35.3)	107 (32.8)	15 (48.4)
≥140	629 (49.4)	32 (47.8)	224 (46.0)	184 (51.1)	177 (54.3)	12 (38.7)
HR (beats/min) (N/A = 2)		81.0 (73.5–90.0)	81.0 (71.0–92.0)	82.0 (74.0–95.0)	85.0 (76.0–95.0)	80.0 (73.0–88.0)	.004
Temp. (°C) (N/A = 3)		36.8 (36.5–37.3)	36.8 (36.5–37.4)	36.8 (36.5–37.2)	36.9 (36.5–37.3)	37.0 (36.7–37.3)	.262
ROS (N/A = 1)
Fever	337 (26.5)	18 (26.9)	134 (27.5)	91 (25.3)	87 (26.7)	7 (22.6)	.944
Cough	556 (43.7)	32 (47.8)	201 (41.2)	160 (44.4)	147 (45.1)	16 (51.6)	.587
Sputum	415 (32.6)	24 (35.8)	156 (32.0)	118 (32.8)	107 (32.8)	10 (32.3)	.981
Sore throat	144 (11.3)	7 (10.4)	47 (9.6)	46 (12.8)	41 (12.6)	3 (9.7)	.593
Rhinorrhea	99 (7.8)	6 (9.0)	38 (7.8)	27 (7.5)	24 (7.4)	4 (12.9)	.847
Myalgia	191 (15.0)	4 (6.0)	80 (16.4)	55 (15.3)	48 (14.7)	4 (12.9)	.270
Fatigue	74 (5.8)	2 (3.0)	32 (6.6)	21 (5.8)	18 (5.5)	1 (3.2)	.754
Shortness of breath	251 (19.7)	13 (19.4)	88 (18.0)	64 (17.8)	78 (23.9)	8 (25.8)	.191
Headache	161 (12.7)	4 (6.0)	71 (14.5)	46 (12.8)	38 (11.7)	2 (6.5)	.225
Altered mentality	13 (1.0)	1 (1.5)	8 (1.6)	0 (0.0)	4 (1.2)	0 (0.0)	.188
Nausea/Vomiting	75 (5.9)	4 (6.0)	33 (6.8)	22 (6.1)	15 (4.6)	1 (3.2)	.722
Diarrhea	97 (7.6)	1 (1.5)	42 (8.6)	27 (7.5)	26 (8.0)	1 (3.2)	.271
Comorbidity
DM	332 (26.1)	14 (20.9)	111 (22.7)	102 (28.3)	97 (29.8)	8 (25.8)	.137
HTN	570 (44.8)	23 (34.3)	178 (36.5)	167 (46.4)	183 (56.1)	19 (61.3)	<.001
Heart Dz (N/A = 4)	127 (10.0)	8 (11.9)	39 (8.0)	37 (10.3)	41 (12.6)	2 (6.5)	.260
Lung Dz	61 (4.8)	7 (10.4)	19 (3.9)	16 (4.4)	16 (4.9)	3 (9.7)	.122
CKD	26 (2.0)	1 (1.5)	11 (2.3)	5 (1.4)	7 (2.1)	2 (6.5)	.405
Cancer (N/A = 1)	53 (4.2)	3 (4.5)	27 (5.5)	9 (2.5)	11 (3.4)	3 (9.7)	.106
Liver Dz (N/A = 40)	27 (2.1)	3 (4.5)	8 (1.7)	5 (1.4)	10 (3.2)	1 (3.3)	.315
RDAD (N/A = 41)	12 (0.9)	0 (0.0)	9 (1.9)	2 (0.6)	1 (0.3)	0 (0.0)	.128
Dementia (N/A = 41)	117 (9.2)	20 (29.9)	62 (13.1)	20 (5.7)	15 (4.8)	0 (0.0)	<.001

All categorical variables are given in numbers (percentage). Percentages may not total to 100 due to rounding. Continuous nonparametric variables are given as the median (IQR). A Chi-square test or Fisher’s exact test was used for categorical variables. The Mann–Whitney U test was used for continuous nonparametric variables (p-value < .1 is statistically significant).

Severe infection^†: outcome of invasive mechanical ventilation, extracorporeal membrane oxygenation, multiorgan failure or death.

Definition of abbreviations: BMI: body mass index; N/A: not available; ICU: intensive care unit; SBP: systolic blood pressure; HR: heart rate; Temp: temperature; ROS: review of system; DM: diabetes mellitus; HTN: hypertension; Dz: disease; CKD: chronic kidney disease; RDAD: rheumatic disease/autoimmune disease; IQR: interquartile range.

Table 2. Univariable analysis of severe infection^† and death.

	Total (n = 1272)	Severe infection (n = 136)	Nonsevere infection (n = 1127)	p-Value	Death (n = 117)	Survival (n = 1155)	p-Value
Age (years)				<.001			<.001
60–69	684 (53.8)	28 (20.6)	647 (57.4)		18 (15.4)	666 (57.7)
70–79	378 (29.7)	49 (36.0)	329 (29.2)		42 (35.9)	336 (29.1)
≥80	210 (16.5)	59 (43.4)	151 (13.4)		57 (48.7)	153 (13.2)
Sex				<.001			.001
Female	750 (59.0)	56 (41.2)	691 (61.3)		51 (43.6)	699 (60.5)
Male	522 (41.0)	80 (58.8)	436 (38.7)		66 (56.4)	456 (39.5)
ICU (N/A = 8)	106 (8.3)	66 (48.5)	40 (3.5)	<.001	54 (46.2)	52 (4.5)	<.001
BMI (kg/m²)				.001			<.001
<18.5	67 (5.3)	15 (11.0)	51 (4.5)		15 (12.8)	15 (12.8)
18.5–22.9	488 (38.4)	52 (38.2)	434 (38.5)		46 (39.3)	46 (39.3)
23.0–24.9	360 (28.3)	23 (16.9)	335 (29.7)		18 (15.4)	342 (29.6)
25.0–29.9	326 (25.6)	41 (30.1)	281 (24.9)		35 (29.9)	291 (25.2)
≥30.0	31 (2.4)	5 (3.7)	26 (2.3)		3 (2.6)	28 (2.4)
Comorbidity
DM	332 (26.1)	58 (42.6)	272 (24.1)	<.001	52 (44.4)	280 (24.2)	<.001
HTN	570 (44.8)	85 (62.5)	483 (42.9)	<.001	73 (62.4)	497 (43.0)	<.001
Heart Dz (N/A = 4)	127 (10.0)	25 (18.4)	102 (9.1)	.001	21 (17.9)	106 (9.2)	.005
Lung Dz	61 (4.8)	13 (9.6)	48 (4.3)	.012	12 (10.3)	49 (4.2)	.007
CKD	26 (2.0)	11 (8.1)	15 (1.3)	<.001	9 (7.7)	17 (1.5)	<.001
Cancer (N/A = 1)	53 (4.2)	12 (8.8)	41 (3.6)	.009	12 (10.3)	41 (3.6)	.001
Liver Dz (N/A = 40)	27 (2.1)	3 (2.2)	24 (2.2)	1.000	3 (2.6)	24 (2.2)	1.000
RDAD (N/A = 41)	12 (0.9)	1 (0.7)	11 (1.0)	1.000	1 (0.9)	11 (1.0)	1.000
Dementia (N/A = 41)	117 (9.2)	34 (25.0)	83 (7.6)	<.001	34 (29.1)	83 (7.5)	<.001

All categorical variables are given in numbers (percentage). Percentages may not total to 100 due to rounding. A chi-square test or Fisher’s exact test was used for categorical variables. p-Value <.1 is statistically significant.

Severe infection^†: outcome of invasive mechanical ventilation, extracorporeal membrane oxygenation, multiorgan failure or death.

Definition of abbreviations: BMI: body mass index; ICU: intensive care unit; N/A: not available; SBP: systolic blood pressure; HR: heart rate; Temp: temperature; ROS: review of system; DM: diabetes mellitus; HTN: hypertension; Dz: disease; CKD: chronic kidney disease; RDAD: rheumatic disease/autoimmune disease; IQR: interquartile range.

Table 3. Multivariable logistic regression results for risk of severe infection^† and death in COVID-19 patients aged 60 years or older.

	Severe infection^†		Death
	Adjusted OR	95% CI	Adjusted OR	95% CI
BMI (kg/m²)
<18.5	1.99	0.96–3.96	2.23	1.06–4.52
18.5–22.9	Reference		Reference
23.0–24.9	0.55	0.31–0.94	0.50	0.27–0.91
25.0–29.9	1.13	0.70–1.83	1.13	0.68–1.89
≥30.0	1.86	0.56–5.16	1.15	0.25–3.77
Sex
Female	Reference		Reference
Male	2.61	1.76–3.93	2.28	1.49–3.52
Comorbidity
DM	1.72	1.15–2.58	1.94	1.26–2.98
HTN	1.94	1.29–2.94	1.96	1.27–3.06
Heart Dz (N/A = 4)	1.78	1.04–2.96	1.69	0.94–2.92
Lung Dz	1.91	0.89–3.86	2.13	0.96–4.41
CKD	4.45	1.73–11.17	3.55	1.30–9.20
Cancer (N/A = 1)	2.68	1.26–5.38	3.54	1.65–7.17
Dementia (N/A = 41)	4.55	2.72–7.55	5.55	3.28–9.33

Logistic regression was used to determine odds ratio. The 95% confidence interval was used to determine statistical significance.

Severe infection^†: outcome of invasive mechanical ventilation, extracorporeal membrane oxygenation, multiorgan failure or death.

Definition of abbreviations: COVID-19: coronavirus disease 2019; OR: odds ratio; CI: confidence interval; BMI: body mass index; DM: diabetes mellitus; HTN: hypertension; Dz: disease; CKD: chronic kidney disease; N/A: not available.

Data availability statement

Raw data were generated by the Korea Centre for Disease Control and Prevention. Derived data supporting the findings of this study are available from the corresponding author (JO) on request.