Higher levels of cortisol in evening saliva is linked to smaller total brain volume.

Cortisol is a hormone that, when produced at high levels (often in response to emotional stress) can have a toxic effect on the hippocampus area of the brain – a region with animportant role in memory. Lenore J. Launer, from the National Institute on Aging (Maryland, USA), and colleagues assessed 4,244 people, average age of 76 years and who did not have dementia., enrolled in the Agee, Gene/Environment Susceptibility (AGES)-Reykjavik Study.  Subjects were assessed via MRI for brain volume, and their saliva was collected at-home 45 minutes after awakening and at night. Higher evening cortisol associated with smaller total brain volume, with the smaller volumes observed in all brain regions, but significantly smaller in gray matter than in white matter regions.  Further, higher evening cortisol associated with poorer cognitive functioning. In contrast, higher levels of morning cortisol associated with slightly greater normal white matter volume and better processing speed and executive functioning. The study authors submit that: “In older persons, evening and morning cortisol levels may be differentially associated with tissue volume in gray and white matter structures and cognitive function.”

Geerlings MI, Sigurdsson S, Eiriksdottir G, Garcia ME, Harris TB, Gudnason V, Launer LJ.  “Salivary cortisol, brain volumes, and cognition in community-dwelling elderly without dementia.”  Neurology. 2015 Aug 19. pii: 10.1212/WNL.0000000000001931.