Household cooking fuel use and intrinsic capacity trajectories in middle-aged and older adults: a longitudinal cohort study

BACKGROUND: Intrinsic capacity is a key indicator of healthy ageing. Household air pollution from cooking fuels may influence functional ageing, yet longitudinal evidence remains limited. This study examined the association between cooking fuel use and trajectories of intrinsic capacity. METHODS: Data were obtained from four waves (2011-2018) of the China Health and Retirement Longitudinal Study, including 11,368 adults aged ≥45 years. Group-based trajectory modelling was used to identify intrinsic capacity trajectories, and multinomial logistic regression was applied to examine associations with cooking fuel use. RESULTS: Three intrinsic capacity trajectories were identified: low (18.1%), moderate (35.5%), and high (46.4%). Compared with solid fuel use, the use of clean cooking fuel was associated with higher odds of having the moderate (OR 1.48, 95% CI 1.30-1.70) and high trajectories (OR 2.10, 95% CI 1.81-2.43). Longer duration of solid fuel use was associated with lower odds of belonging to favourable trajectories (P for trend <0.001). These associations were consistent across subgroup analyses. CONCLUSIONS: Cooking fuel use was associated with intrinsic capacity trajectory. Clean fuel use was linked to more favourable trajectory patterns, whereas prolonged solid fuel use was associated with less favourable trajectories. These findings highlight household air pollution as a potentially modifiable environmental determinant of functional ageing.