Reduced hair cortisol concentrations are associated with improved emotional wellbeing in older adults following repeated forest walking.

The main hypothesis of this study in older adults is that repeated walks in a forest but not an urban environment for one month lead to reduced chronic stress compared to the previous month without any intervention. This was achieved by the measurement of cumulative cortisol concentrations in hair. Older adults of both sexes (n = 54; 71 ± 6.2 years) participated in a randomised, parallel-group trial. They were randomly assigned to a forest or an urban walking group. They completed two 40-minute walking sessions per week over one month. Hair samples and morning, as well as afternoon salivary samples, were collected at baseline and following one month of walking interventions.A significant reduction in cumulative hair cortisol was observed during the month of repeated forest but not urban walking compared to the previous month, indicating decreased chronic stress. Salivary cortisol concentrations decreased in the forest group only. No differences in salivary alpha-amylase activity were noticed. Walking activities had no negative impact on the diurnal rhythmicity of stress markers. Quality of life measures showed improvements in emotional well-being in the forest group. A negative correlation was found between hair cortisol and certain quality of life dimensions in urban but not forest groups. Repeated forest walks affect objective measures of chronic stress in older adults, evidenced by lower cumulative hair cortisol concentrations and improved emotional well-being. These findings encourage incorporating forest-based interventions into mental health programs for older adults aimed at enhancing well-being, stress coping, and cognitive functions.