Monitoring of physical activity using accelerometry in patients with chronic obstructive pulmonary disease

Abstract

Objectives

The main objective of the study was to analyze the characteristics of physical activity in people with Chronic Obstructive Pulmonary Disease. Secondarily, the association between the number of steps per day and the baseline sociodemographic and clinical characteristics of the sample was evaluated.

Methods

A multicenter longitudinal descriptive study was carried out in four Primary Care centers in Madrid. The participants were 80 people diagnosed with COPD. In a face-to-face interview, sociodemographic information and clinical characteristics were collected. Physical activity was measured over a week with a three-axis accelerometer that recorded wear time, number of steps per day, walking time, and time spent performing light, moderate, vigorous, and very vigorous physical activity.

Results

The average time of use of the accelerometer was 6.84 ± 0.4 days. The number of daily steps taken was 6902.24 ± 3994.01 with a walking time of 78.07 ± 41.85 min/day. The time of light physical activity was 69.66 ± 46.42 min/day, of moderate activity 92.76 ± 42.91 min/day, of vigorous activity 9.93 ± 13.6 min/day and of very active activity vigorous 0.26 ± 0.64 min/day.

Conclusions

The participants mainly carried out physical activity of light and moderate intensity, complying with current recommendations, while the time dedicated to vigorous and very vigorous activities was reduced and was insufficient.

Resumen

Objetivo

El objetivo principal del estudio fue analizar las características de la actividad física en personas con Enfermedad Pulmonar Obstructiva Crónica (EPOC). De forma secundaria, se evaluó la asociación entre el número de pasos al día y las características sociodemográficas y clínicas basales de la muestra.

Metodología

Se realizó un estudio descriptivo longitudinal multicéntrico, en cuatro centros de Atención Primaria en Madrid. Los participantes fueron 80 personas diagnosticadas de EPOC. En una entrevista presencial, se recogió información sociodemográfica y sobre características clínicas. La actividad física se midió durante una semana con un acelerómetro de tres ejes que registró el tiempo de uso, el número de pasos al día, el tiempo de caminata y el tiempo dedicado a realizar actividad física ligera, moderada, vigorosa y muy vigorosa.

Resultados

El tiempo medio de uso del acelerómetro fue de 6,84 ± 0,4 días. El número de pasos diarios realizados fue de 6902,24 ± 3994,01 con un tiempo caminado de 78,07 ± 41,85 minutos/día. El tiempo de actividad física ligera fue de 69,66 ± 46,42 minutos/día, de actividad moderada 92,76 ± 42,91 minutos/día, de actividad vigorosa 9,93 ± 13,6 minutos/día y de actividad muy vigorosa 0,26 ± 0,64 minutos/día.

Conclusiones

Los participantes realizaron principalmente actividad física de intensidad ligera y moderada, cumpliendo con las recomendaciones actuales, mientras el tiempo dedicado a actividades vigorosas y muy vigorosas fue reducido resultando insuficiente.

What is known?

Physical activity is a relevant variable in the assessment of COPD patients due to its clinical and prognostic implications.

What does this study contribute?

This study uses accelerometry to analyse the type and duration of physical activity performed by people with COPD in the sample and identifies the negative association between daily step count and dyspnoea, and the BODE index. This could be useful for early detection of declines in the index and to prevent deterioration in function and quality of life in these people.

Introduction

Chronic obstructive pulmonary disease (COPD) is a heterogeneous lung disease characterised by chronic respiratory symptoms due to airway and/or alveolar abnormalities that cause persistent and progressive airflow obstruction.¹ COPD is one of the most important non-communicable diseases worldwide and is associated with high morbidity and mortality, making its management a public health problem due to the high economic and social burden it entails.²

The most common clinical manifestations are cough, sputum production, fatigue, and dyspnoea.¹ These symptoms are associated with a reduction in quality of life, in exercise tolerance, and in physical activity levels.¹ Patients with COPD have lower levels of physical activity than the healthy reference population and a natural long-term decline in physical activity.³

Physical activity in COPD patients has been shown to be directly related to quality of life, exercise tolerance and exacerbation frequency, and is the strongest predictor of all-cause mortality.^4–6 Therefore, the assessment of physical activity has become an increasingly important variable in evaluating it overall.

Physical activity can be measured by self-report through interviews or self-report questionnaires such as the International Physical Activity Questionnaire (IPAQ), the Yale Physical Activity Questionnaire,^7,8 or through fitness monitors such as pedometers and accelerometers.⁹ Although self-report methods are the most commonly used in routine clinical practice, they have been shown to overestimate physical activity.¹⁰ On the other hand, fitness monitors include triaxial accelerometers, which are validated tools that have been shown to be the most objective for quantifying physical activity, as they allow measurement of the amount and intensity of physical activity.¹¹

The assessment of patients with COPD should include the measurement of physical activity using objective tools, and as primary care is the first level of care and is where most monitoring and control of chronic patients takes place, we believe that this assessment could be carried out in this setting. An accurate assessment of the type and duration of physical activity would make it possible to assess compliance with physical activity recommendations and help to identify early declines in physical activity, allowing the prescription of community interventions to promote physical activity and prevent decline in functional capacity and quality of life, thus improving secondary prevention.

Therefore, the main objective of this study was to describe physical activity in patients with COPD and, secondarily, to investigate its relationship with the sociodemographic and clinical characteristics of the sample studied.

Material and methods

Design, follow-up, and participants

An observational, descriptive, and longitudinal study was conducted. The study was approved by the Ethics Committee of the Hospital Clínico San Carlos (Madrid) (22/126-EC) and the Comisión Local de Investigación Este de la Gerencia Asistencial de Atención Primaria (Primary Care Management Local Research Commission East (Madrid)) (04/22_E). The study was conducted in accordance with the Declaration of Helsinki.

The study population was recruited from different primary care centres in Madrid (Spain) using non-probabilistic convenience sampling.

The inclusion criteria for participation in the study were: 1) confirmed diagnosis of COPD, defined as a post-bronchodilator forced expiratory volume in one second/forced vital capacity (FEV₁/FVC) < .7; 2) clinical stability (no hospitalisation in the last 6 mo). Exclusion criteria were: 1) cognitive impairment affecting comprehension; 2) having received respiratory rehabilitation in the previous 6 mo; 3) severe orthopaedic problems preventing independent walking.

Study procedure

Participation in the study required three face-to-face visits. On the first visit, the interested parties received information about the study and the researcher checked that they met the inclusion criteria. On the second visit, after signing the informed consent form, information was collected on sociodemographic and clinical characteristics, and the use of the accelerometer was explained. The participant had to wear the device on their back, at waist level, throughout the day except when sleeping and when showering.^12,13 Finally, after using the activity monitor for 7 days, the person returned the device during a third visit. All measurements were taken by the same researcher in a face-to-face evaluation.

Variables

Sociodemographic and clinical characteristics

Information was collected on age, sex, occupation, and level of education. At a clinical level, body mass index, smoking habit, (pack-years) and previous clinical conditions were recorded using the Charlson index, which measures comorbidities through 19 categories reflecting different chronic medical conditions that are scored from one to six according to their severity.¹⁴ Lung function was evaluated by post-bronchodilation forced spirometry, which recorded the predicted FEV₁ percentage and the relationship between this and the FVC. The severity of airflow limitation was categorised according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification.¹⁵ The severity of the disease was measured using the BODE index (body mass index, obstruction, dyspnoea, exercise), which estimates the prognosis of the disease through the sum of four markers that are scored from 0 to 3. These markers are body mass index, the severity of the obstruction according to the percentage of the predicted FEV_1, the degree of dyspnoea, and the distance covered in the 6 min walk test.¹⁶

In addition, the level of dyspnoea was recorded using the modified Medical Research Council (mMRC) scale, which assesses the degree of dyspnoea from 0 to 4 according to the functional limitation it causes in activities of daily living, and lower limb fatigue using the modified Borg scale, which rates fatigue from 0 (‘none’) to 10 points (‘maximum’).^17,18 Finally, the type of medication used was recorded.

Physical activity

Physical activity was assessed using a 3-axis accelerometer (DynaPort accelerometer; McRoberts BV, The Hague, The Netherlands), which recorded daily step count, and the time spent taking light, moderate, vigorous, and very vigorous physical activity. The type of activity was defined according to the guidelines of the American College of Sports Medicine, i.e., light activity was defined as 1.5–3 metabolic equivalents (METs), moderate activity as 3–6 METs, vigorous activity as 6–9 METs, and very vigorous activity as >9 METs.¹⁹ A measurement was considered valid if the time of use was ≥ 8 h for at least 3 consecutive days.^13,20

Statistical analysis

Statistical analysis was performed using SPSS® software based on a 5% significance level (p < .05) for a 95% confidence interval. First, a descriptive analysis was carried out in which the quantitative variables were expressed as mean and standard deviation and the qualitative variables as absolute and relative frequencies and percentages. The correlation between quantitative variables was analysed using Spearman’s correlation coefficient (Rho). A correlation was considered low if r < .3, moderate between .3–.6, and strong if r > .6.²¹ For the association between quantitative and qualitative variables, normality tests were first carried out using the Kolmogorov-Smirnov test. In the case of non-parametric distribution, the Wilcoxon-Mann-Whitney test and the Kruskal-Wallis test were used.

Finally, a multivariate linear regression analysis was performed with the mean daily step count as the dependent variable. All variables with a p-value of less than .20 in the univariate analysis were included in this analysis and, in an attempt to control for collinearity bias, variables that were part of a multiparametric scale were not included, such as dyspnoea by mMRC, distance walked in 6 min, FEV₁ or body mass index, as they are components of the BODE index.

Results

Description of the sample

The total sample consisted of 80 participants with a mean age of 72.09 ± 7.9 years and a predicted FEV₁ of 65.10 ± 15.41%. Other socio-demographic and clinical characteristics are shown in Table 1.

Table 1.

Sociodemographic and clinical characteristics of the sample (n = 80).

	Mean ± SD	Nº (%)
Sociodemographic characteristics
Age (years)	72.09 ± 7.90
Sex
Female		22 (27.5%)
Occupation
Active		14 (17.5%)
Retired		65 (81.3%)
Temporary disability		1 (1.3%)
Level of education
School graduate		60 (75%)
Secondary education		17 (21.3%)
Higher education		3 (3.8%)
Smoking habit
Active smokers		24 (30%)
Pack/year index	46.65 ± 28.93
Clinical characteristics
BMI (kg/m^2)	28.84 ± 5.37
Comorbidities (Charlson index)	2.09 ± 1.19
Lung function
FEV1 (% predicted)	65.10 ± 15.41
FEV1/FVC	59.63 ± 8.03
Severity of obstruction (GOLD)
Mild		8 (10%)
Moderate		62 (77.5%)
Severe		3 (12.5%)
Classification according to symptoms (GOLD)
Group A		26 (32.5%)
Group B		44 (55%)
Group C		5 (6.3%)
Group D		5 (6.3%)
Severity of COPD (BODE index)
Dyspnoea (mMRC scale)	1.29 ± .62
Grade 0		6 (7.5%)
Grade 1		46 (57.5%)
Grade 2		27 (33.8%)
Grade 3		1 (1.3%)
Lower limb fatigue (modified Borg)	2.81 ± 3.03
Medication
LAMA monotherapy		7 (8.8%)
LABA monotherapy		4 (5%)
Dual bronchodilation (LAMA + LABA)		22 (27.5%)
LABA + inhaled corticosteroid		16 (20%)
Triple therapy		30 (37.5%)

BODE: Body mass index, obstruction, dyspnoea, exercise; BMI: Body mass index; FEV₁: Forced expiratory volume in one second; FVC: Forced vital capacity; GOLD: Global initiative for chronic obstructive lung disease; LABA: Long-acting beta-agonists; LAMA: Long-acting muscarinic antagonists; mMRC: Modified medical research council; SD: Standard deviation.

Physical activity

The accelerometer was used for an average of 6.84 ± .4 days with a usage time of 13.81 ± 2.58 h. The daily step count was 6,902.24 ± 3,994.01 with a walking time of 78.07 ± 41.85 min. The time spent on light physical activity was 69.66 ± 46.42 min/day, moderate activity 92.76 ± 42.91 min/day, vigorous activity 9.93 ± 13.6 min/day, and very vigorous activity .26 ± .64 min/day.

Association between daily step count and sociodemographic and clinical characteristics

The associations between daily step count and socio-demographic and clinical characteristics are shown in Tables 2 and 3. The results showed a low correlation between daily step count and the degree of dyspnoea and FEV₁, and a moderate correlation with the BODE index. The distributions of these associations are shown in Fig. 1: Correlation between daily step count and forced expiratory volume in one second (FEV₁); Fig. 2: Correlation between steps/day and the modified Medical Research Council (mMRC) dyspnoea scale; and Fig. 3: Correlation between daily step count and the BODE index.

Table 2.

Correlation between the number of steps/day and sociodemographic and clinical characteristics.

Variables	Correlation r	p-value
Sociodemographic characteristics
Age		.083
Smoking
Pack/year		.308
Clinical characteristics
BMI		.75
Comorbidities		.065
FEV1	.234	.037*
FEV1/FVC		.479
BODE index	–.311	.005**
Dyspnoea (mMRC scale)	–.229	.041*
Lower limb fatigue (modified Borg)		.499

BODE: Body mass index, obstruction, dyspnoea, exercise; BMI: Body mass index; FEV₁: Forced expiratory volume in one second; FVC: Forced vital capacity; mMRC: Modified medical research council.

*

p < .05.

**

p < .01.

Table 3.

Association between number of steps/day and sociodemographic and clinical characteristics.

Variables	p-value
Sociodemographic characteristics
Sex	.620
Occupation	.177
Level of education	.629
Smoking
Smoking habit	.085
Clinical characteristics
GOLD severity	.015*
Medication
LAMA monotherapy	.677
LABA monotherapy	.230
Dual bronchodilation (LAMA + LABA)	.401
LABA + inhaled corticosteroid	.897
Triple therapy	.911

GOLD: Global initiative for chronic obstructive lung disease; LABA: Long-acting beta-agonists; LAMA: Long-acting muscarinic antagonists.

*

p < .05.

Figure 1.

Correlation between steps/day and forced expiratory volume (FEV1).

Figure 2.

Correlation between steps/day and degree of Dyspnoea according to the modified Medical Research Council (mMRC).

Figure 3.

Correlation between steps/day and BODE index.

Multivariate analysis showed that the BODE index was the only variable able to predict the daily step count (Table 4). Thus, for each unit increase in the BODE index, the step count decreased by 1,020 units.

Table 4.

Multivariate analysis of number of steps/day.

Variable	Coefficient B	95% confidence interval	p-value
Age	–99.14	–235.14–36.85	.15
BODE index	–1020.54	–1698.32–362.76	.003*
Charlson index	–186.11	–974.79–602.56	.64
Smoking	564.7	–1571.50–2700.91	.60

BODE: Body mass index, obstruction, dyspnoea, exercise.

*

p < .01.

Discussion

This study objectively describes the characteristics of physical activity, type of activity, and duration undertaken by people with COPD in the sample. The results of this study show that the participants performed mainly light and moderate physical activity.

To the authors’ knowledge, there are few studies in Spanish samples that evaluate physical activity using accelerometry, and in these studies it is measured in the context of a pulmonary rehabilitation programme, since the variance in step count has been shown to be influenced by this circumstance. This research is therefore relevant as it describes physical activity within a longitudinal design without intervention and outside the hospital setting.^22,23

With regard to daily step count, the values obtained are similar to those recorded in Spanish samples of patients with COPD. However, these data are higher than those of other cohorts from different countries, which could be due to the fact that physical activity is a very complex phenomenon, influenced by cultural and social factors, the environment, and climate, among other factors.^22–24

In terms of time spent per week in moderate to vigorous physical activity (MVPA ≥ 3MET), the values reported are almost identical to other cohorts whose baseline characteristics in terms of obstruction severity, dyspnoea, and FEV₁ (% predicted) were very similar to ours.²⁵

Participants in the sample therefore met the WHO recommendations of 150–300 min of moderate physical activity per week.²⁶

Note that this energy expenditure corresponds to activities such as walking at 4–5 km/h, Pilates, or dancing.²⁷ The time spent on vigorous physical activity, however, was significantly lower, which means that the WHO recommendations were not met. This could be because activities that correspond to vigorous physical activity require an energy expenditure of more than 6 METs (climbing stairs, carrying weights, or running at 6 km/h) and are much more demanding, and therefore patients with COPD are limited in performing this type of activity due to their degree of dyspnoea and muscle fatigue, among other factors.²⁸

The negative association between daily step count and dyspnoea is consistent with previous literature, as one of the main barriers to physical activity is the feeling of breathlessness.²⁸ It has been reported that patients with greater breathlessness reduce the time they spend walking because of the discomfort they experience. A negative association has also been found between step count and the BODE index. Since FEV₁ values, dyspnoea measured by the mMRC scale, and exercise tolerance measured by the 6-min walk test, all components of the BODE index, have been shown to be the clinical characteristics of COPD patients with the highest predictive value for step count, their correlation with this indicator is clear.²⁹

The limitations of the study are its short-term longitudinal design, which does not allow an analysis of physical activity behaviour in the medium and long term, and the fact that most participants had moderate airflow obstruction, which limits the extrapolation of the results obtained to people with mild or severe COPD.

In future studies, it would be interesting to analyse the progression of physical activity over time and to have larger samples with greater variability in characteristics to better understand physical activity in people with COPD.

Conclusion

The people with COPD in the sample studied, most of whom had moderate airflow obstruction, mainly engage in light to moderate physical activity in their daily lives, in line with recommendations. However, the time spent on vigorous activity is insufficient. In addition, a negative association was found between daily step count, dyspnoea, and the BODE index.

Funding

The study was funded by the Complutense University of Madrid through transformative agreements for the publication costs of this manuscript.

Acknowledgements

We would like to thank all the study participants and the professionals at the Las Fronteras Health Centre for their collaboration in recruiting participants.