24-hour accelerometry in COPD: Exploring physical activity, sedentary behavior, sleep and clinical characteristics

Figures & data

Figure 1 CONSORT flowchart.

Abbreviation: GOLD, Global Initiative for Obstructive Lung Disease.

Table 1 Participant characteristics stratified by COPD status, reported as mean (SD) for continuous data

	COPD (n=109)	Controls (n=135)	P-value
Demographics
Age (years)	65.7 (7.1)	58.5 (9.0)	<0.001
Gender: female/male	42/67	89/46	<0.001
Employment status: employed/unemployed/retired	28/12/69	72/7/56	<0.001
Household incomea (£):<£18,000/£18,000–30,999/£31,000–51,999/£52,000–99,999/≥£100,000	40/31/17/6/0	15/39/37/34/4	<0.001
Respiratory health
Smoking status: current/former/never	18/78/12	8/60/67	<0.001
Pack years (median [IQR])	38.9 (29.0)	10.6 (18.0)	<0.001
FEV1 (L)	2.0 (0.7)	2.8 (0.6)	<0.001
FEV1%pred	76.2 (17.8)	107.0 (17.9)	<0.001
FVC (L)	3.6 (1.0)	3.9 (0.8)	0.016
FEV1/FVC	56.0 (11.2)	72.8 (6.3)	<0.001
mMRC score (median [IQR])	1 (1)	0 (1)	<0.001
Perceived general health
General health index value	0.775 (0.181)	0.893 (0.109)	<0.001
General health VAS score (median [IQR])	80 (25)	90 (15)	<0.001
Body composition
BMI (kg/m^2)	28.6 (5.6)	26.9 (5.2)	0.016
Percentage body fat	28.8 (8.6)	29.7 (8.2)	0.426
Waist circumference (cm)	99.9 (13.9)	89.9 (14.4)	<0.001
Physical function
ISWT (m)	387.4 (158.5)	580.1 (189.5)	<0.001
QMVC (kg)	34.9 (13.2)	38.3 (14.7)	0.067
Grip strength (kg)	35.7 (10.9)	36.0 (10.5)	0.820
Usual walking speed: slow/average/fairly brisk/brisk	29/63/15/2	3/73/56/3	<0.001

Note:

a 15 (13.7%) COPD patients and six (4.5%) controls did not provide an answer.

Abbreviations: BMI, body mass index; FEV₁%pred, FEV₁ percentage predicted; ISWT, incremental shuttle walk test; IQR, interquartile range; mMRC, modified Medical Research Council; QMVC, quadriceps maximal voluntary contraction; VAS, visual analog scale.

Table 2 PCA for sleep duration, VMCPM, sedentary time, light intensity PA, MVPA, and VPA (99.5% of variance explained for COPD and 99.6% of variance explained for controls, P<0.001)

Accelerometry variables	COPD				Controls
	Percent of variance	Component loading			Percent of variance	Component loading
		Component				Component
		1	2	3		1	2	3
VMCPM	54.8	0.897	0.428	0.010	18.2	0.679	0.714	0.135
Stationary		−0.849	−0.113	−0.513		−0.410	−0.839	−0.355
LPA		0.953	0.098	−0.282		0.108	0.982	−0.148
MVPA	27.2	0.242	0.961	−0.109	63.8	0.969	0.237	0.039
VPA		0.138	0.983	−0.076		0.979	0.184	0.039
Sleep	17.5	−0.039	−0.151	0.998	17.5	0.042	0.030	0.999

Notes: COPD: component 1, “low-intensity movement”; component 2, “high-intensity movement”; and component 3, “sleep.” Controls; component 1, “high-intensity movement”; component 2, “low-intensity movement”; and component 3, “sleep.” Bold values indicate the main contributing variables to each component.

Abbreviations: MVPA, moderate-to-vigorous PA; PA, physical activity; VMCPM, vector magnitude counts per minute (average movement intensity); VPA, vigorous PA; LPA, light PA.

Figure 2 Scatterplot of sedentary time against MVPA (minutes/day) for individuals with COPD, stratified by their ST (</≥600 minutes/day) and MVPA (</≥20 minutes/day).

Notes: Solid circles: COPD; blank circles: controls.
Abbreviations: MVPA, moderate-to-vigorous PA; PA, physical activity; ST, stationary time.

Figure 3 A schematic comparing the characteristics associated with sleep, low-intensity movement, and high-intensity movement for patients and controls.

Notes: +, positive correlation between variables; -, negative correlation between variables.
Abbreviations: F, female; M, male.

Table 3 Linear regression analyses exploring the associations of “low-intensity movement,” “high-intensity movement,” and “sleep” components with participant characteristics for COPD and control groups

Variables	COPD						Controls
	Low-intensity movement		High-intensity movement		Sleep		Low-intensity movement		High-intensity movement		Sleep
	R	P-value	R	P-value	R	P-value	R	P-value	R	P-value	R	P-value
Demographics
Age	−0.067	0.490	−0.393	<0.001	0.061	0.529	−0.044	0.611	−0.348	<0.001	−0.190	0.028
Gendera	−0.143	0.138	−0.096	0.319	−0.267	0.005	−0.094	0.279	−0.070	0.420	−0.254	0.003
Respiratory health
mMRC score	−0.348	<0.001	−0.105	0.278	0.206	0.032	−0.219	0.012	−0.104	0.235	0.090	0.304
FEV1	−0.187	0.332	−0.008	0.065	−0.293	0.002	−0.080	0.356	0.089	0.308	−0.055	0.530
Perceived general health
Mobilityb	−0.250	0.009	−0.133	0.168	0.142	0.141	−0.046	0.601	−0.120	0.169	−0.038	0.665
Self-careb	−0.150	0.120	−0.201	0.036	0.061	0.528	0.064	0.465	−0.096	0.270	−0.069	0.431
Activitiesb	−0.218	0.024	−0.173	0.074	0.185	0.057	−0.013	0.883	−0.109	0.215	−0.166	0.058
Painb	−0.149	0.121	−0.124	0.200	0.111	0.250	0.031	0.720	−0.202	0.020	−0.165	0.057
General health indexb	0.216	0.025	0.148	0.129	−0.126	0.195	−0.032	0.721	0.149	0.090	0.172	0.049
Body composition
BMI	−0.206	0.031	−0.072	0.460	0.016	0.870	−0.349	<0.001	−0.046	0.599	−0.061	0.486
Percentage body fat	−0.147	0.126	−0.014	0.883	0.189	0.049	−0.234	0.007	−0.070	0.426	0.076	0.386
Waist circumference	−0.277	0.004	−0.155	0.107	−0.073	0.453	−0.319	<0.001	−0.133	0.127	−0.140	0.108
Physical function
ISWT	0.260	0.007	0.317	0.001	−0.211	0.031	0.265	0.002	0.231	0.007	0.015	0.865
Usual walking speedc	0.215	0.024	0.199	0.038	−0.134	0.166	0.157	0.069	0.254	0.003	0.053	0.543

Notes:

a 0= female, 1= male;

b 1= no, 2= slight, 3= moderate, 4= severe, 5= unable/extreme problems; and

c 1= slow, 2= average, 3= fairly brisk, 4= brisk. Bold values represent P<0.05.

Abbreviations: BMI, body mass index; ISWT, incremental shuttle walk test; mMRC, modified Medical Research Council.

Figure S1 Scatterplot of component scores for “low-intensity movement” and “high-intensity movement.”

Notes: Solid circles: COPD; blank circles: controls.

Abbreviation: PCA, principal components analysis.