Relationship between balance and physical activity measured by an activity monitor in elderly COPD patients

Figures & data

Table 1 Characteristics of the COPD patients and healthy controls

Characteristics	COPD (n=22)	Control (n=13)	P-value
Age (years)	71.6 (6.9)	71.5 (5.6)	0.982
Height (m)	1.65 (0.05)	1.65 (0.06)	0.906
Body weight (kg)	60.0 (6.7)	62.2 (9.3)	0.432
BMI (kg⋅m^−2)	22.1 (2.9)	22.7 (2.5)	0.530
FVC (L)	2.85 (0.95)	2.99 (0.88)	0.698
FEV1 (% predicted)	52.8 (20.6)*	94.7 (26.7)	<0.001
FEV1/FVC (%)	46.8 (14.0)*	86.5 (11.2)	<0.001

Notes: Data are mean (SD) unless indicated otherwise;

* indicates differences are significant.

Abbreviations: BMI, body mass index; FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second; SD, standard deviation.

Table 2 Balance, physical activity, and the possible confounders in COPD patients and controls

Outcome measures	COPD (n=22)	Healthy control (n=13)	Mean difference	95% CI	P-value
OLST (seconds)	30.4 (21.5)*	46.4 (18.6)	−16.0	−30.5, −1.4	0.033
SPPB total (point)	10.7 (1.7)*	12 (12.12)	–	–	0.013
Standing balance test (point)	4 (4.4)	4 (4.4)	–	–	–
4MGS (m⋅s^−1)	0.94 (0.20)*	1.42 (0.30)	−0.48	−0.65, −0.30	<0.001
5STST (seconds)	11.05 (3.19)*	7.75 (1.77)	3.30	1.3, 5.3	0.002
Daily steps (steps per day)	4,546 (2,992)*	8,713 (3,480)	−4,167	−6,808, −1,527	0.003
MV-PA (min⋅day^−1)	13.9 (14.0)*	27.4 (19.1)	−13.5	−24.9, −2.1	0.022
MMRC (points)	1.8 (0.7)	–	–	–	–
QMVC (kg/kg)	0.68 (0.22)	–	–	–	–
6MWD (m)	423.7 (138.3)	–	–	–	–
CAT (point)	14.1 (4.7)	–	–	–	–

Notes: Data are mean (SD) or median (25 percentile, 75 percentile);

* differences are significant.

Abbreviations: OLST, one-leg standing test; SPPB, Short Physical Performance Battery; 4MGS, 4 m gait speed; 5STST, five-times sit-to-stand-test; MV-PA, time spent in moderate-to-vigorous physical activity per day; MMRC, modified Medical Research Council; QVMC, quadriceps isometric maximum voluntary contraction normalized to body weight; 6MWD, 6-minute walk distance; CAT, COPD assessment test; CI, confidence interval; SD, standard deviation.

Table 3 Correlations among balance, physical activity, and the possible confounders in the COPD patients (n=22)

Outcome measures	Daily steps	MV-PA	BMI	FEV1	MMRC	QMVC	6MWD	CAT
Balance
OLST	0.821*	0.645*	0.217	−0.285	−0.462	0.504*	0.509*	−0.043
SPPB total	0.563*	0.621*	0.056	0.018	−0.504*	0.341	0.514*	0.288
4MGS	0.364	0.260	−0.137	0.399	−0.523*	0.534*	0.642*	0.026
5STST	−0.299	−0.384	−0.154	−0.002	0.424	−0.285	−0.406	−0.291
Physical activity
Daily steps	1.00	0.892*	0.190	−0.060	−0.636*	0.546*	0.660*	−0.120
MV-PA	0.892*	1.00	0.257	0.165	−0.558*	0.370	0.654*	−0.036

Notes: This table shows correlations among balance and physical activity and the possible confounders in the COPD patients (n=22);

* correlations are significant.

Abbreviations: OLST, one-leg standing test; SPPB, Short Physical Performance Battery; 4MGS, 4 m gait speed; 5STST, five-times sit-to-stand test; MV-PA, time spent in moderate-to-vigorous physical activity per day; BMI, body mass index; FEV₁, forced expiratory volume in 1 second; MMRC, modified Medical Research Council; QVMC, quadriceps isometric maximum voluntary contraction normalized to body weight; 6MWD, 6-minute walk distance; CAT, COPD assessment test.

Figure 1 Correlations between balance measures and physical activity and possible confounders in subjects with COPD (n=22).

Notes: (A) OLST and (B) SPPB.

Abbreviations: OLST, one-legged standing test; SPPB, Short Physical Performance Battery; MV-PA, time spent in moderate-to-vigorous physical activity per day; 6MWD, 6-minute walk distance; QMVC, quadriceps isometric maximum voluntary contraction normalized to body weight; MMRC, modified Medical Research Council.

Figure 2 Correlations between physical activity and possible confounders in subjects with COPD (n=22).

Notes: (A) Daily step and (B) MV-PA.
Abbreviations: MV-PA, time spent in moderate-to-vigorous physical activity per day; 6MWD, 6-minute walk distance; QMVC, quadriceps isometric maximum voluntary contraction normalized to body weight; MMRC, modified Medical Research Council.

Table 4 The independent variables influencing the OLST times in the COPD patients (n=22)

Variables	β	t-value	P-value
Daily steps	0.819	4.799	<0.001
6MWD	0.209	1.231	0.253
QMVC	0.064	0.446	0.661
Adjusted R^2	0.704

Note: The data are the results of a multivariable regression Analysis 1 using the OLST times as the dependent variable and daily steps, QMVC, and 6MWD as predictors.

Abbreviations: OLST, one-leg standing test; β, standardized partial regression coefficient; adjusted R², adjusted coefficient of determination; 6MWD, 6-minute walk distance; QMVC, quadriceps isometric maximum voluntary contraction normalized to body weight.

Table 5 The independent variables influencing daily steps in the COPD

Variables	β	t-value	P-value
OLST	0.705	4.666	<0.001
6MWD	0.339	1.729	0.103
MMRC	−0.041	−0.211	0.836
QMVC	0.077	0.527	0.605
Adjusted R^2	0.731

Note: This table shows the results of multivariable regression Analysis 2 using daily steps as the dependent variable and the OLST times, MMRC, QMVC, and 6MWD as predictors.

Abbreviations: OLST, one-leg standing test; β, standardized partial regression coefficient; adjusted R², adjusted coefficient of determination; 6MWD, 6-minute walk distance; MMRC, modified Medical Research Council; QMVC, quadriceps isometric maximum voluntary contraction normalized to body weight.

Table 6 The independent variables influencing MV-PA in the COPD patients (n=22)

Variables	β	t-value	P-value
OLST	0.519	2.743	0.014
6MWD	0.645	2.471	0.024
MMRC	0.183	0.753	0.462
Adjusted R^2	0.518

Note: This table shows the results of multivariable regression Analysis 3 using MV-PA as the dependent variable and the OLST times, MMRC, and 6MWD as predictors.

Abbreviations: β, standardized partial regression coefficient; adjusted R², adjusted coefficient of determination; MV-PA, time spent in moderate-to-vigorous physical activity per day; OLST, one-leg standing test; 6MWD, 6-minute walk distance; MMRC, modified Medical Research Council.