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.

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.

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.

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.

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