The association between daily exacerbation symptoms and physical activity in patients with chronic obstructive pulmonary disease

Figures & data

Table 1 Patient characteristics at discharge from pulmonary rehabilitation or acute care

Characteristics	Patients (N=21)
Sex, male, n (%)	14 (66.7)
Age (years)	63.0 (9.9)
FEV1 (L)	1.2 (0.4)
FEV1 % predicted	40.8 (14.3)
BMI (kgm^−2)	23.9 (6.1)
Smoking status, n (%)
Never-smoker	1 (4.8)
Former smoker	15 (71.4)
Current smoker	5 (23.8)
GOLD grade, n (%)
II	5 (23.8)
III	8 (38.1)
IV	8 (38.1)
Exacerbations in previous year	2.3 (1.9)
Number of comorbidities per patient	3.4 (1.9)
Comorbidity type, n
Cardiovascular disease group	25
Cerebrovascular disease group	1
Metabolic disease group	1
Musculoskeletal disease group	5
Psychiatric disease group	6
Other diseases	31
1-min STS test repetitions	22.4 (8.0)

Note: Data are presented as mean (SD), unless otherwise stated.

Abbreviations: BMI, body mass index; FEV₁, forced expiratory volume in 1 s; GOLD, Global Initiative for Chronic Obstructive Lung Disease; 1-min STS, 1-minute sit-to-stand.

Table 2 Multivariable analysis assessing the association between daily EXACT score and daily physical activity, adjusted for relevant confounders (model 1)

Variable	Effect	95% CI	z-value	P-value
Daily EXACT scorea
1 point increase	−54.4	−80.8 to −28.1	−4.1	<0.001
9 point increase	−490.0	−727.3 to −252.7	−4.1	<0.001
12 point increase	−653.3	−969.7 to −336.9	−4.1	<0.001
Age (years)	1.0	−36.0 to 37.9	0.1	0.96
Sex (ref: male)
Female	74.3	−952.3 to 1,101.0	0.1	0.89
FEV1 (L)	820.7	145.5 to 1,496.0	2.4	0.02
BMI (kgm^−2)	−34.8	−112.8 to 43.1	−0.9	0.38
1-min STS test repetitions	49.6	−2.5 to 101.7	1.9	0.06
Number of comorbidities per patient	−471.7	−717.1 to −226.2	−3.8	<0.001
Smoking status (ref: current-smoker)
Former smoker	1,070.0	73.7 to 2,066.3	2.1	0.04
Non-smoker	3,968.5	2,988.1 to 4,948.8	7.9	<0.001
Number of exacerbations in the previous year	−8.3	−150.4 to 133.7	−0.1	0.91

Notes:

a Score range: 0–100 points. Bayesian Information Criterion =25,709.

Abbreviations: BMI, body mass index; EXACT, EXAcerbations of Chronic pulmonary disease Tool; FEV₁, forced expiratory volume in 1 s; 1-min STS, 1-minute sit-to-stand; ref, reference.

Figure 1 Fitted regression lines for individual patients for the association between daily step count and daily EXACT score from model 1. The figure shows the predicted number of daily steps for the given EXACT score. There appears to be a weaker association (slope more horizontal) at higher numbers of steps, and more between-patient variation at lower EXACT scores (fewer symptoms).

Abbreviation: EXACT, EXAcerbations of Chronic pulmonary disease Tool.

Table 3 Adjusteda associations of each respiratory symptom domain with daily physical activity, estimated from individual models (models 2–4)

E-RS symptom domain score	Effect	95% CI	z-value	P-value	BIC
Breathlessnessb (model 2)	−153.4	−257.8 to −49.0	−2.9	0.004	25,748
Cough and sputumb (model 3)	−127.8	−212.7 to −42.9	−3.0	0.003	25,743
Chest symptomsb,c (model 4)	−187.7	−268.8 to −106.7	−4.5	<0.001	25,731

Notes:

a All 3 models were adjusted for the same confounders as in model 1;

b all effects are per 1-point increase. Breathlessness score range: 0–17 points, cough and sputum score range: 0–11 points, chest symptoms score range: 0–12 points;

c chest symptoms include chest tightness, discomfort and congestion.

Abbreviations: BIC, Bayesian Information Criterion; E-RS, Evaluating Respiratory Symptoms in chronic obstructive pulmonary disease.

Figure 2 Individual courses of daily step count and daily total EXACT score over the 3-month study period for patients who did not have an exacerbation (A) and patients who did have an exacerbation (B). Diamonds indicate the start date of clinically defined event-based exacerbations, gray boxes indicate the 28-day recovery period after the start of an exacerbation and black squares indicate adverse events (unrelated to COPD exacerbations). Patients 16 (14 days) and 19 (1 day) were admitted to hospital due to their exacerbations; all other exacerbations were home-based. Adverse events were constipation (patient 5), numbness in feet (patient 7), purulent infection on the arm (8), stomach pain and diarrhea (14), electric cardioversion (16), severe sunburn to chest (18), tooth removal and armpit abscess (19) and crushed ribs (21). No adverse events required hospitalization.

Notes: Numbers in the lower left-hand corner represent an individual patient (in random order).
Abbreviations: COPD, chronic obstructive pulmonary disease; EXACT, EXAcerbations of Chronic pulmonary disease Tool.