In this study, formaldehyde exposure was shown to have a long-term detrimental impact on cognitive health in a relatively young population.

• Using the French CONSTANCES cohort, researchers sought to assess the link between occupational exposure to formaldehyde and cognitive impairment in middle-aged and young-old adults (≥45 years).

• Of 75,322 participants (median age 57.5 years, 53% women), 8% had exposure to formaldehyde during their professional life.

• In these participants, there was a higher risk of global cognitive impairment post-adjusting for confounders (age, gender, education, income, solvent exposure, Effort–Reward Imbalance, night shift, repetitive work, and noisy work).

• They exhibited a higher risk of cognitive impairment for all cognitive domains investigated.

• Longer exposure duration and high cumulative exposure index were found to be linked with cognitive impairment, with a dose–effect association for exposure duration.

• An association of recent exposure with impairment in all cognitive domains was found.

• Time did not completely reduce formaldehyde-related cognitive deficits particularly in highly exposed people.