A new study suggests that contact with nature can alleviate the aging immune system. Older adults who partook in six-months of horticultural therapy showed reduced T-cell exhaustion and inflammation. The findings were published in The Journals of Gerontology, Series A.
As the immune system ages and declines, older adults are left with a greater risk of infection, inflammatory diseases, and cancer. While there are existing medical interventions that target age-related changes in the immune system, these procedures are costly and difficult to carry out over a wide population.
Study authors Glenn Choon Lim Wong and team describe a psychosocial intervention that has shown promise among the older population. Horticultural Therapy (HT) combines the mental health benefits associated with nature activities with the added physical benefits of breathing clean, less-polluted air and engaging in physical exercise. The researchers conducted an intervention study to explore HT as a potential candidate for improving immunological fitness.
The researchers assigned 59 Singapore adults between the ages of 61 and 77 to either receive a six-month HT intervention or to be on a waiting list. The therapy group participated in 15 hour-long sessions across the six months, at first weekly, and then monthly. The sessions included a mixture of indoor horticulture, park visits, and outdoor gardening. Blood samples were collected at baseline, three months into the intervention, and six months in.
The researchers found that the horticultural therapy was linked to lower T-cell exhaustion, a phenomenon which is characteristic of the aging immune system. T-cells are immune cells that are involved in fighting foreign substances and, as the authors describe, the exhaustion of these cells gets in the way of the body’s ability to overcome infections and cancers.
“HT has already been institutionalized in some hospitals to reinforce mental fortitude in cancer patients and our findings suggest that by lowering the expression of exhaustion markers, HT may also be beneficial in promoting T cell anti-tumour surveillance in older adults,” the researchers say.
Further, the HT group showed reduced inflammaging, which is a “chronic state of low-grade inflammation” that occurs in older adults and is thought to contribute to disease. This was demonstrated through lower levels of the inflammatory marker interleukin 6 (IL-6).
The authors acknowledge that their sample was small and mostly female and that future studies should attempt to replicate these effects among a larger, more diverse sample. They also suggest that future studies should explore whether or not these immune-boosting effects are partially driven by the physical exercise involved in nature-based activities.
Despite these limitations, the authors say the findings offer preliminary evidence that horticultural therapy can not only improve well-being and cognition but may also boost the aging immune system.
The study, “Horticultural Therapy Reduces Biomarkers of Immunosenescence and Inflammaging in Community-Dwelling Older Adults: A Feasibility Pilot Randomized Controlled Trial”, was authored by Glenn Choon Lim Wong, Ted Kheng Siang Ng, Jia Le Lee, Pei Yi Lim, Sean Kai Jie Chua, Crystal Tan, Michelle Chua, Janice Tan, Samantha Lee, Angelia Sia, Maxel K.W. Ng, Rathi Mahendran, Ee Heok Kua, Roger C.M. Ho, and Anis Larbi.