Cooking with biomass fuels increased the risk for cognitive impairment and cognitive decline among the oldest-old Chinese adults (2011–2018): A prospective cohort study

•Evidence on biomass fuel use and cognitive ability is scarce among the oldest-old.•Cooking with biomass fuels was associated with greater risk of cognitive impairment and cognitive decline.•Switching from biomass to clean fuels is beneficial to postponing cognitive aging.•Participants who engaged in irregular exercise or not living with family were more susceptible to the adverse effect.•Ventilation was associated with lower cognitive impairment and cognitive decline risk.