Cluster-randomised trial on participatory community-based outdoor physical activity promotion programs in adults aged 65–75 years in Germany: protocol of the OUTDOOR ACTIVE intervention trial

The current demographic change in Europe is characterized by decreasing birth rates, rising life expectancy and an ageing population. This development is posing challenges on private, social and societal levels, and healthy ageing has become one key strategy to fight the expected added burden of the health system [1]. Physical activity (PA) is declining with age, and it is less prevalent in women compared to men and in lower compared to higher socioeconomic groups [2]. Despite its known benefits for health, more than two-thirds of the age group 65 years and older do not meet minimal PA recommendations in Germany [3] and raising these levels, preferably in community-based or neighborhood-based settings, forms one of the seven national specific health targets in the area of healthy ageing [4]. Cochrane reviews on PA promotion have repeatedly criticized the lack of intervention studies with sound methodology using objective PA measurements for evaluation [5–7].

Various factors of all ecological levels (intrapersonal, interpersonal, and environmental) contribute to the uptake and maintenance of any type of PA [8]. However, due to a lack of longitudinal studies and studies using objective PA measurements, a differentiation between correlates and determinants is barely possible [7, 8]. Factors that could play a causal role for PA in adults in general are perceived fitness, intention to exercise, self-efficacy, social support, PA history, and other psychosocial variables [8–11]. Apart from these intra- and interpersonal characteristics, the engagement in PA is strongly dependent on environmental factors [8, 12–14] and environmental intervention has been shown to be potentially successful previously [15]. Research in older adults is still scarce; a review from 2004 implies that among environmental factors, safety and aesthetics could play the most important roles in older age groups [16]. A review by van Cauwenberg and colleagues on determinants for PA [17] found inconsistent results for the age group 65+, which the authors attribute to “methodological issues within this developing research field”. Only two of the 29 included studies were using objective PA measurements, and most studies failed to differentiate between types of activity. The latter would be important for detecting associations between PA and environmental factors [17]. As any engagement in PA, outdoor PA has direct beneficial health effects on muscle strength, motor skills and cardiorespiratory fitness. Outdoor PA also has indirect effects that are not attributed to the physical movement alone, including higher Vitamin D levels, mental wellbeing and raised emotional scores through exposure to sensory engagement [18]. EEC readings show the direct impact of the PA environment [19]. In a recent study, older adults who were physically active outdoors at least once a week showed higher levels of PA compared with those who were physically active indoors only [20]. Moreover, outdoor PA gives the opportunity for social interaction and does not require sports facilities.

The success of PA promotion programs is heterogeneous [21, 22] and depends amongst others on the type of intervention and presence of a methodological framework for the development of the intervention [23]. Community-based participatory research (CBPR) frameworks show great potential for PA intervention as they involve the community, especially if they follow an ecological model [10]. CBPR have been shown to be effective for work-related health promotion [24], and they are useful to reduce health disparities [25]. Experience with CBPR in the development of PA promotion programs in older adults is limited. Despite the poor evidence base, PA interventions following a social ecological approach and integrating individual and environmental levels are considered to be most effective [8–11].

The OUTDOOR ACTIVE study is part of the Physical Activity And Health Equity: Primary Prevention For Healthy Ageing (AEQUIPA) project, a regional prevention research network in Northwest Germany funded by the German Federal Ministry of Education and Research (BMBF). The AEQUIPA research network includes several interlinked projects which employ theory-based empirical research methods to develop, implement and evaluate PA and mobility interventions for older adults aged 65–75 years. The network’s overall aim is to strengthen the evidence base for PA in the context of healthy ageing [26]. AEQUIPA is in its second funding phase (02/2018–01/2021), the first funding phase started in 02/2015. In the OUTDOOR ACTIVE pilot study, which took place during the first funding phase, a community-based physical activity program was developed in one urban district in the city of Bremen, Germany, where a CBPR approach, the PRECEDE-PROCEED model (PPM), was used [27]. Based on the experiences, a short track PPM for participatory development of PA programs in older adults in urban settings was developed. Moreover, an open toolbox of ready-to-use intervention components to be used in the participatory process was started and will be continuously updated.

The objective of the OUTDOOR ACTIVE intervention trial is to formally test and investigate efficacy of the developed short track PPM. For this, a cluster randomized trial (CRT) will be carried out in eight random subdistricts in the city of Bremen, Germany. In four of the randomly selected subdistricts, the short track PPM will be applied and the resulting intervention program implemented, the other four randomly selected subdistricts will serve as controls, where no intervention is taking place.

PA is an important component for healthy ageing with many documented benefits both for society and the individual [30]. Thus, the proportion of persons meeting the recommendations for PA should be as high as possible in all age groups. In older adults, PA promotion is especially important, since albeit the potential gain for this group is large, engagement in PA is decreasing with age [31]. Especially outdoor PA, with its added external stimuli is a valuable health resource in older age [32].

In the OUTDOOR ACTIVE intervention trial, we formally evaluate the efficacy of a participatory community-based approach for tailoring an outdoor PA promotion for older adults to a random subdistrict with its given actors and structures. If successful, partners will be sought to implement the intervention in all subdistricts of Bremen such that control subdistricts will also directly benefit from the trial. Moreover, the approach and a ready-to-use toolbox for applying it will be published and made available to other communities. The OUTDOOR ACTIVE intervention trial will provide detailed information on PA intervention for older adults in an urban setting. The use of an objective method for the assessment of the main outcome, physical activity, helps eliminating recall and social desirability bias [33]; and ensures international comparability of the results. Through the participatory nature of the study it will provide valuable insights into drivers and barriers to PA in this group, and it will inform policy makers and other stakeholders how to benefit from the results.