Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide1 and the seventh leading cause of disability-adjusted life years.2 The Global Burden of Disease Study 20153 estimated 174 million cases of COPD globally and its prevalence is expected to increase in the upcoming years.4,5

Physical activity (PA) levels are reduced in most patients with COPD when compared to healthy peers,6 which have a negative impact on clinical outcomes (such as an increased risk of exacerbations, hospitalizations and mortality7) and can lead to the development of comorbidities, which further contribute to physical inactivity.8 Additionally, a decrease in PA levels over time across all severity grades of COPD has been demonstrated, in parallel with a worsening of lung function and health status.9 It has been suggested that increasing daily PA might be equally effective as smoking cessation to prevent morbidity and mortality in patients with COPD, although the consequences of continuous inactivity in this population might still be underestimated.10 Recent research has highlighted that even small changes in PA (e.g., increasing activity by 600 steps per day11) can be clinically meaningful for patients.10

The Global Initiative for Chronic Obstructive Lung Disease (GOLD)5 highlights the potential of technology-based interventions to provide accessible means to enhance PA in daily life. The value of technology became even more relevant during the COVID-19 pandemic, where several in-person healthcare services had to be adapted to reduce the burden on healthcare systems.12 Mobile applications (apps) aiming to promote PA may be a promising solution to help patients with COPD acquire healthy habits in their own environment, as smartphones are ubiquitous in daily life.13,14 In 2021, 67% of the world population subscribed to mobile services; of those, 75% were smartphone connections, and an increase to 84% is expected by 2025.15 Smartphone devices as a tool to promote PA in patients with COPD have shown small improvements in the short-term and no effects in the long-term.16 Poor adherence may be caused, among other things, by problems related to the device, affecting the effectiveness of these apps.16 Thus, technological features are a fundamental aspect of patient adherence and app success.17 Studies have suggested that different features can influence the effectiveness of PA promotion apps, such as goal setting adapted to the users’ context and progress14,18 and social media features,19 and these aspects have been identified as enablers of PA engagement in patients with COPD.20,21 Recent reviews have described the most common features in smartphone apps for PA promotion.17,18,22–26 However, these studies did not address apps designed for populations with specific health conditions, such as COPD. A review from Donevant and colleagues27 explored the relationship between the app features and PA outcomes in mobile health studies involving chronic respiratory diseases, diabetes and hypertension, but they have not stratified the findings by health condition. Given the added complexity and challenge in PA promotion and behavior change in patients with COPD,21 research is warranted to explore how smartphone app features have been implemented in this specific population.

The aim of this systematic review was to identify the smartphone apps developed, tested and/or implemented for PA promotion in patients with COPD, as well as to identify the technological features implemented by those apps, based on the framework of Mollee et al. (2017).26 This framework was developed to ensure a good coverage of the important features of apps aimed to encourage PA behavior.

This review identified the technological features implemented in smartphone apps designed to promote PA in patients with COPD, along with the scores of these features using the framework developed by Mollee et al.26 The 19 apps identified in the present study included a relatively low number of features for PA promotion, with an average of 10 features per app (i.e., 26% of the 38 possible features), which were mostly related to PA monitoring, data analysis, feedback/support and adaptation. These findings may be useful in the development of interventions aiming to promote PA in patients with COPD using mobile solutions.

A possible explanation for the low number of features included in each app was previously pointed out by Mollee et al.26 The authors hypothesized that it could be related to the technical and conceptual complexity of the implementation of some features. For example, in their study, Vorrink et al.43 mentioned that battery life posed a major problem while developing the app, thus not all desired options, such as GPS-tracking and continuous measurement, were possible to implement due to the limited capacity of the smartphone battery. In addition, as shown in Table 1, several apps were not specific for PA promotion; therefore, they may have scored low in the PA features framework due to the primary aim of the app (i.e., self-management), where PA promotion is only a module. For example, the MH-COPD programme51 registered eight PA-related features; however, there was a substantial number of features related to other self-management modules (e.g., education, symptom management, smoking behavior). Nonetheless, the authors decided to include these apps since they include a component of PA promotion.

This review showed some heterogeneity in the categories/features implemented in the smartphone apps – while some features or categories were frequently applied, others were rarely or never implemented in the apps. Considering the most implemented features, the ‘advice on physical activity’ is particularly important since information and education on PA have been identified in the literature as an enabler for PA promotion following Pulmonary Rehabilitation, by increasing individuals’ understanding of the associated health benefits.21 The ‘Information and analysis’ features (i.e., presentation of the user's PA in visual/textual format) were also common. These features are important when promoting active lifestyles in patients with COPD, as they can recognize their personal improvements and may be more engaged/motivated by the outcomes, thus feeling more empowered to maintain the PA levels achieved.21 Some apps supported the use of external hardware, such as smartbands for daily PA tracking.31,32,35,37,38,41,42,46,48,50,52,53 This feature may allow greater flexibility in monitoring PA in specific situations, e.g., when the patient is at home and leaves the smartphone on the table or elsewhere, as smart bands can still collect PA data. However, connection or synchronization issues between the external sensor and the app were identified in three studies.35,41,44 These issues should be considered when developing apps for PA promotion as they can lead to lower patient adherence to the app.

The features related to the category Adaptation were also frequently implemented, which differs from the PA apps for healthy adults identified in the work of Mollee and colleagues,26 where these were one of the least addressed features.26 This could indicate that there is a greater effort to customize the features of PA promotion apps developed for patients with COPD. In fact, personalization features, such as adapting the user's goals based on individual behavior/needs, have shown to increase the effectiveness of PA apps in the general population.14,23 Furthermore, personalization and self-goal setting have been described as enablers for PA engagement in patients with COPD,20 the latter being especially relevant, as self-regulatory strategies are not only identified as determinants of PA in these patients,20,21 but also as an important aspect within behavior change techniques, helping people to modify their PA levels.54 This may be addressed in future research on PA promotion apps for patients with COPD.22,23 In addition, it would be useful to identify the factors that influence patients’ PA behavior, described in the literature (i.e., barriers and enablers20,21), which are addressed in each app to understand whether the apps consider the (partially) modifiable factors when promoting PA and/or adjust recommendations based on non-modifiable factors.

Weather forecast integration was not implemented in any of the apps, even though converging evidence has demonstrated that adverse weather (e.g., temperature, rain) and air quality conditions can have a negative impact on COPD symptoms55 and PA levels.20,56 In a RCT that implemented a smartphone app to promote daily PA,31 included in this review, patients were reminded they could exercise at home on days when the weather prevented them from going outside; however, these reminders were sent manually by the researchers. Thus, integrating weather forecast information in the apps could alleviate this barrier by providing opportunities to engage in PA even in case of bad weather. Furthermore, the apps could be connected to wearable devices that would detect changes in air pollution levels and provide appropriate advice (e.g., to exercise at home or select the route with lower levels of air pollution). There are several commercial wearable/portable solutions for environmental monitoring in the market, although their accuracy is still questionable.57 As sensor/wearable technology is rapidly advancing, it is possible that such solutions will exist in future apps for PA promotion to enable better choices of where and when to perform activities and provide personalized recommendations.57,58

Calendar integration was implemented less often, although this feature could help patients establish a routine and, therefore, be an important strategy to create PA habits.20,21 The number of apps with the possibility to contact an expert, and with social features, was scarce. These features may be relevant considering the importance that social support has on PA engagement in patients with COPD.59 Individuals’ relationships with others may have a large impact on their PA levels – feeling understood and encouraged to be physically active by family members, friends and peers can facilitate an active lifestyle.20,21 Moreover, support from healthcare professionals may be important for individuals, as it can create a sense of trust.21

This review has some limitations that need to be acknowledged. Firstly, the authors did not consider the Usability category, as described in the framework developed by Mollee et al.26 In this category, the apps were scored for clarity and attractiveness, which required interaction with the app. In the present review, the authors excluded this category because the apps were not possible to download, and the authors could not provide a reliable scoring simply by analyzing the images provided in the articles (when available). Nevertheless, this aspect could be of interest, since it is not known how the clarity and attractiveness of the apps may influence patient adherence, and if the number of features in the app are related to its usability. Mollee et al.26 found that easy-to-find information in an app was not compromised by the number of implemented features, but there was a moderate positive correlation between the number of features and the attractiveness score.

Secondly, the fact that none of the apps were downloaded or used by the authors restricted the number of features identified. Often, studies did not provide a detailed description of the apps, including only information about the fundamental features; therefore, it is possible that certain features were overlooked in the present study. This is also a weakness of the research in this area – although there were 19 apps identified to promote PA in patients with COPD, most are still not available online for clinical use.

Thirdly, the scoring process of the technological features using the framework of Mollee et al.26 was not always easy to perform, as shown by the results of inter-rater agreement available in the Supplementary material S3. Specifically, some questions (i.e., items and subitems) were not described in sufficient detail in the original paper to make a clear decision on whether a specific feature was present or not in the smartphone app, which sometimes led to some subjectivity in the process. For example, the two raters had slightly different interpretations of the question “Does the app give the user feedback based on their physical/social context?” (Support and feedback category), concerning the definition of “physical”. One reviewer considered this as a “environmental context”, and the other as a “biological context”, being the latter the agreed interpretation. Even so, the average inter-rater agreement was moderate, which shows that scoring the apps features using this classification framework is feasible.

Finally, the analysis of individual, clinical and sociodemographic characteristics of patients who participated in studies implementing the smartphone apps was beyond the scope of this review, although it could provide important information on who would benefit most from this type of technology, as there is no ‘one size fits all’ approach. A previous study found that patients with COPD who use mobile apps in daily life are younger and have a higher physical capacity than those who do not use them (age: 64.2 ± 8.9 vs. 69.2 ± 6.3 years; six-minute walking distance: 462.9 ± 91.7 vs. 414.9 ± 82.3 m, respectively), although 73% of the sample reported being interested in using a COPD-specific app for PA promotion, if it was available.60 Future research should identify the best candidates for interventions using mobile solutions.

Among the strengths, this review was the first to address technological features of smartphone apps to promote PA in patients with COPD. It identified the most used features and the ones that may need more attention in future development of these apps.28 Future research should address the impact of these apps on patients’ PA levels, and how the results relate to the presence/absence of specific technological features of the apps. Likewise, it would be important to adjust the features of the apps based on the factors associated with PA engagement in patients with DPOC (e.g., symptoms, having a dog, taking care of grandchildren).61–63

This review identified the technological features of 19 smartphone apps designed to promote PA in patients with COPD, based on the framework developed by Mollee and colleagues.26 The apps included 10 out of 38 possible features, with the most prevalent features being “advice on physical activity”, “data in visual format” and “progress in visual format”. Weather forecast integration, calendar integration, possibility to contact an expert, and social features were less often implemented, although they may be relevant to improve patients’ PA behavior. Future research should explore the impact of these apps on patients’ PA levels, as well as the effect of the presence/absence of specific technological features on the results.

The authors declare there is no conflict of interests.