D2.388 - Greening office spaces: the impact of indoor plants on autonomic nervous system activity

Most of the global population resides in urban areas with limited access to green spaces, particularly in office-dominated settings. Indoor plants have emerged as a promising approach to enhance worker health and well-being. The autonomic nervous system (ANS) can be influenced by increased contact with green areas and natural elements in urban environments. This work aimed to assess the impact of introducing indoor plants in urban offices on workers' ANS activity through a randomized controlled trial.

The study was conducted from February 2023 to March 2024 in Porto, Portugal. The intervention involved placing pots of Sansevieria trifasciata, Dracaena fragrans, and Chlorophytum comosum in 12 office spaces at a density of one pot per 9 m², while 11 offices served as controls. Participants working in the studied offices for at least 6 months were invited to be subjected to pupillometry assessments to evaluate ANS activity. Pupillometry evaluations were conducted before and after a 14-day intervention period in a semi-dark environment, focusing on the participants' right eye since no side-to-side difference was anticipated. Overall, 130 office workers were engaged in the study (intervention: n=75; control: n=55).

Pupillometry parameters indicated significant changes in the intervention group. Initial pupil diameter decreased from 5.7 mm to 5.4 mm (z=-3.585, p<0.001), final pupil diameter from 4.0 mm to 3.7 mm (z=-3.704, p<0.001), and constriction amplitude increased from 30.8% to 32.1% (t(49)=2.139, p=0.037). The control group showed no significant pupillometry changes. This suggests that having indoor plants in offices contributes to enhancing parasympathetic activity, which is associated with a greater sense of relaxation among workers.

These findings underscore the potential of indoor plants as a practical and scalable green solution for fostering physiological relaxation in office environments. Integrating indoor plants into workplace design represents an actionable strategy to enhance worker well-being and support sustainable urban health solutions.