Frequency of laughter and depression onset among older adults: A 6-year longitudinal study from the Japan Gerontological Evaluation Study.

Background: Laughter has been associated with mental and physical health benefits, but longitudinal evidence on whether laughter in daily life protects against depression remain limited. This study aimed to examine whether the frequency of laughter in daily life is associated with the risk of depression onset among older adults.

Methods: We analyzed data from 32,666 adults aged ≥65 years participating in the Japan Gerontological Evaluation Study, a three-wave cohort conducted over six-years. Frequency of laughter was assessed in 2019 using a self-administered questionnaire with response categories: "almost every day", "1-5 days per week", "1-3 days per month", and "never or almost never". Depression onset during 2016-2022 was defined using the Geriatric Depression Scale. We fitted a modified Poisson regression model to estimate the adjusted risk ratios and their 95 % confidence intervals (CIs), controlling potential confounders measured in 2016.

Results: During follow-up, 4805 (14.7 %) participants developed depression. Compared to those who laughed almost every day, those who laughed 1-5 days per week had 1.25 (95 % CI 1.09-1.44) times, those who laughed 1-3 days per week had 1.26 (95 % CI 1.05-1.52) times, and those who laughed never had 1.49 (95 % CI 1.18-1.89) times higher risks of depression. A significant dose-response trend was observed (P for trend<0.001).

Conclusion: Lower frequency of laughter in daily life was associated with an increased risk of depression onset in older adults. These findings suggest that frequent laughter may play a role in depression prevention in later life.