Study design
COLD
This is a controlled pilot field-study on parallel groups in an intention-to-treat setting. Participants were recruited from the population using the Health and Social Service Centre of Sipoo and all live in the municipality of Sipoo. Although situated only 17 km from the city center of Helsinki, the capital of Finland, Sipoo is a rural area with abundant green and blue spaces. The population density is 65 persons/kmThe intervention program adapted in this study was developed during the Terveysmetsä (transl. Health Forest) project, a national network project established in 2014 (The Nature-group program included learning more about local outdoor areas and nature itself, the biotopes visited were chosen to provide varied nature experiences, including forests, farmland, lakes, and seashore. Accompanied by nature guides the group practiced simple sensory exercises that enhance contact with nature and its microbiome. A more detailed program is attached in The Sports-group participated in an exercise program and met weekly in community sports facilities. Exercise we define as a planned, structured, repetitive, and purposeful form of physical activity that aims to improve or maintain one or more components of physical fitness. The sports program was planned and executed by professional sports instructors in cooperation with health professionals and included both aerobic and anaerobic exercise as well as team sports. The content of the exercise program was planned according to current best practice and considering the participants physical ability. Details of the program are attached in The intensity and duration of the physical activity as well as the social interaction were designed to be as alike as possible in the compared groups. Both groups were offered a meal or snack during or after the session, with the aim of increasing cohesion. The intervention was free of charge, but travel expenses (mostly by car or bus, <10 km) were not covered. With a maximum of 20 participants the groups met 7 times during an 8-week period. Every session took place in a different location. This enabled the participants in the Nature-group to become familiar with the different outdoor areas, and the Sports-group to become familiar with local sports facilities. The planned activity level was modest, equaling approximately 2 km of walking at slow pace. The intervention started in 2018 and was planned to go on until 2020, including 160 participants equally distributed between the groups. The participants were considered to have fulfilled the program if they attended 5 or more sessions. Based on previous studies in similar populations, we emphasized a 25% drop-out. The intervention was completed twice a year (spring and autumn) during the years of 2018 and 2019 which causes some variance as Finland is a northern country with dark, and commonly cold winters. The COVID-19 epidemic in 2020 hindered the group interventions reducing the total number of participants. A Nature-group was organized in autumn 2020, but its data is not included in this study due to the contrasting general circumstances. A separate qualitative follow-up study was conducted in 2022 (It was possible to participate the intervention without being part of the study. Participants in the study signed an informed consent form allowing the use of data and giving permission to recontact. Participants were free to withdraw from the study at any time without giving a reason, and this did not interfere with their care in any way. The study was approved by the coordinating Ethical Committee of Helsinki and Uusimaa Hospital District (HUS/3520/2017) and study permission was granted by the municipality (7.2.2018). All data is anonymized and stored at the Finnish Institute for Health and Welfare (THL).