Forest bathing improves inflammatory markers, SpO2, and subjective symptoms related to chronic obstructive pulmonary disease (COPD) in male subjects at risk of developing COPD.

The short version

This randomized crossover trial studied 30 Japanese men, average age 63, who were at risk of developing chronic obstructive pulmonary disease (COPD) — a common lung condition that narrows airways and makes breathing harder over time, and one of the world's leading causes of death. Each man spent one day forest bathing (Shinrin-yoku, the Japanese practice of mindfully immersing yourself in a forest) in a cypress forest, and another day walking a similar distance through a nearby city, in random order — so each person acted as their own comparison. Both walks covered the same distance at the same gentle pace under the guidance of a certified forest therapist, and participants avoided alcohol and ate the same meals throughout the 3-day trip. Researchers measured inflammation markers and oxygen levels in the blood before and after each walk, checked blood-oxygen saturation with a fingertip sensor, and had participants complete standard questionnaires about breathing symptoms, sleep quality, mood, and fatigue. Forest bathing lowered several inflammation markers (CRP, IL-6, and α1-antitrypsin) significantly more than the city walk did, and raised blood-oxygen saturation, while the city walk produced no such oxygen improvement. COPD-related breathing symptoms dropped significantly after forest bathing but stayed about the same after the city walk. Sleep quality improved across most measures after forest bathing, and mood scores showed less anger, confusion, depression, and anxiety, with people feeling notably more energetic than after the city walk. Fatigue and physical discomfort also eased more after time in the forest. Both walks used the same amount of physical effort (confirmed by matched blood-lactate levels), meaning the extra benefits of the forest walk likely came from the forest environment itself — its cleaner air, plant-released aromatic compounds (phytoncides), and calming, multisensory setting — rather than simply from walking. In people at risk of COPD, these results suggest that spending a day in a forest, walking gently and mindfully, may ease inflammation, improve breathing-related symptoms, and boost mood and sleep more than an equivalent walk in the city. Forest bathing is not a treatment for COPD; the authors caution that diagnosed COPD calls for medical supervision and flat, easy trails. The study is small (30 men) and tested only two single days, so it can't yet say whether these benefits last with regular practice or apply to women or other age groups.

Key findings

• In a crossover trial where 30 men at risk of COPD each tried both a day of forest bathing and a day of city walking, forest bathing significantly lowered several blood markers of inflammation (CRP, IL-6, and α1-antitrypsin) more than the equivalent city walk.
• Blood-oxygen saturation (SpO2) rose significantly after forest bathing but did not improve after the city walk, and COPD-related breathing symptoms eased significantly only after the forest day.
• Sleep quality, mood, and fatigue all improved more after forest bathing than after the matched-distance urban walk, even though both walks required the same amount of physical effort.
• The extra benefits of forest bathing are thought to come from the forest environment itself — cleaner air, plant-released aromatic compounds called phytoncides, and a calming multisensory setting — rather than from exercise alone.
• This was a small study of 30 men over just two days, so while forest bathing looks promising as a complementary, low-risk practice for people at risk of COPD, it is not a substitute for medical treatment, and larger and longer studies are needed.

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