Daily home gardening improved survival for older people with mobility limitations: an 11-year follow-up study in Taiwan

Abstract

Aims

To test the hypothesis that gardening is beneficial for survival after taking time-dependent comorbidities, mobility, and depression into account in a longitudinal middle-aged (50–64 years) and older (≥65 years) cohort in Taiwan.

Methods

The cohort contained 5,058 nationally sampled adults ≥50 years old from the Taiwan Longitudinal Study on Aging (1996–2007). Gardening was defined as growing flowers, gardening, or cultivating potted plants for pleasure with five different frequencies. We calculated hazard ratios for the mortality risks of gardening and adjusted the analysis for socioeconomic status, health behaviors and conditions, depression, mobility limitations, and comorbidities. Survival models also examined time-dependent effects and risks in each stratum contingent upon baseline mobility and depression. Sensitivity analyses used imputation methods for missing values.

Results

Daily home gardening was associated with a high survival rate (hazard ratio: 0.82; 95% confidence interval: 0.71–0.94). The benefits were robust for those with mobility limitations, but without depression at baseline (hazard ratio: 0.64, 95% confidence interval: 0.48–0.87) when adjusted for time-dependent comorbidities, mobility limitations, and depression. Chronic or relapsed depression weakened the protection of gardening. For those without mobility limitations and not depressed at baseline, gardening had no effect. Sensitivity analyses using different imputation methods yielded similar results and corroborated the hypothesis.

Conclusion

Daily gardening for pleasure was associated with reduced mortality for Taiwanese >50 years old with mobility limitations but without depression.

Keywords:

• gardening
• mortality
• leisure activity
• survival
• epidemiology

Supplementary materials

Table S1 Baseline demographic and physical characteristics of participants in 1996 stratified by 5-frequency gardening

Table S2 HR and 95% CI of baseline 5-frequency gardening on all-cause mortality and each model mutually adjusted for covariates at baseline

Table S3 HR and 95% CI of baseline 5-frequency gardening on all-cause mortalitya adjusted for time-dependent covariates

Table S4 HR and 95% CI of baseline 5-frequency gardening on all-cause mortality among participants who had limited mobility and no depression at baseline (N=1,145)

Table S5 HR and 95% CI of baseline 5-frequency gardening on all-cause mortality adjusted for time-dependent covariates among people with IADL impairmentsa in 1996 (N=1,415)

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Acknowledgments

We thank Professor Jing-Hsiang Hwang of Academia Sinica for advising us on imputation methods for the missing values, and Bill Franke and Paul Steed for English editing and proofreading. This study is based on the data from the TLSA, provided by the Bureau of Health Promotion, Department of Health, Taiwan. The descriptions or conclusions herein do not represent the viewpoint of the Bureau. The fee of English editing of the revised manuscript was supported by the project funded by the Ministry of Science and Technology (MOST 104-2314-B-006-023).

Disclosure

This work received no outside funding. The authors report no conflicts of interest in this work.