Association of hobby engagement with cognitive decline transitions and healthy life expectancy: evidence from four international ageing cohorts

Global population ageing presents an unprecedented public health challenge, with cognitive deterioration and dementia emerging as leading causes of disability among older adults. Hobby engagement represents a modifiable factor for cognitive health. We conducted a prospective cohort analysis using harmonized longitudinal data from four major ageing surveys encompassing 123,802 participants aged 50 years and older across 31 countries. Cognitive states were classified using standardized composite assessments as normal cognition, mild cognitive decline, severe cognitive decline, and death. Hobby engagement was treated as a time-varying binary exposure in continuous-time multi-state Markov models examining bidirectional cognitive transitions. Cognitive state-specific life expectancy was estimated using multi-state life tables. Hobby engagement was associated with 20–40% lower risk of transitioning from normal to mild cognitive decline in three of four cohorts (hazard ratio [HR] = 0.60–0.80, p < 0.05). Participants showed 15–37% higher rates of recovering from mild to normal cognition in the USA, England, and Europe (HR = 1.15–1.37, p < 0.05). Hobby participants demonstrated gains in healthy cognitive life expectancy of 6.50–9.75 additional years at age 50 across cohorts (p < 0.05), and total life expectancy gains of 3.40–4.50 years in China, England, and Europe (p < 0.05). Time in mild cognitive decline was reduced by 1.25–3.25 years, and severe cognitive decline by 1.40–2.00 years, in most cohorts. These findings indicate that hobby engagement is associated with reductions in cognitive deterioration risk and facilitation of cognitive recovery across diverse ageing populations, supporting extended healthy cognitive life expectancy and compression of cognitive morbidity.