Gardening and subjective cognitive decline: a cross-sectional study and mediation analyses of 136,748 adults aged 45+ years

Background: Given the benefits of gardening for physical and psychological health, we explored whether gardening was associated with lower risks of subjective cognitive decline (SCD), a precursor of dementia, and SCD-related functional limitations. Methods: Included in this cross-sectional study were 136,748 participants aged 45 + years old from the Behavioral Risk Factor Surveillance System 2019 survey, who were then categorized into three groups according to self-reported exercise status: non-exercisers, gardeners, and other exercisers. SCD was assessed via a questionnaire, and SCD-related functional limitations were referred to as having difficulties in engaging in household or social activities due to SCD. The odds ratio (OR) and 95% confidence interval (CI) were calculated to assess the associations of gardening with SCD and SCD-related functional limitations, adjusted for age, sex, socioeconomic status, lifestyle factors, and health status. Mediation analyses were conducted to examine whether the observed association between gardening and SCD was mediated by energy expenditure (MET-hours/week), depression status, and consumption of fruits and vegetables. Results: Overall, 11.1% and 5.4% of participants self-reported experiencing SCD and SCD-related functional limitations, respectively. The adjusted OR for gardeners vs. non-exercisers, was 0.72 (95% CI 0.62–0.83) for SCD and 0.57 (95% CI 0.44–0.73) for SCD-related functional limitations. The observed association between gardening and SCD was explained by higher energy expenditure (39.0%), lower likelihood of having depression (21.5%), and higher consumption of fruits and vegetables (3.4%) (P<0.05 for all). Similar patterns were observed for SCD-related functional limitations. Conclusion: In this nationally representative sample, gardening was associated with better cognitive status, which may be mainly attributed to better depression status and energy expenditure.