(HealthDay News) — Evening and morning cortisol levels in older people may be differentially associated with tissue volume in gray and white matter structures and cognitive function, according to a study published online in Neurology.
Mirjam I. Geerlings, PhD, from the National Institute on Aging in Bethesda, Maryland, and colleagues analyzed data from the Age, Gene/Environment Susceptibility (AGES)-Reykjavik Study. Participants (4,244; mean age, 76 years; 58% women) were without dementia and had 1.5T brain magnetic resonance imaging (MRI), assessment of cognitive functioning and saliva collected at home 45 minutes after awakening and at night.
The researchers found that higher evening cortisol was associated with smaller total brain volume, when adjusted for age, sex, education, intracranial volume, smoking, steroid use, white matter lesions and brain infarcts on MRI. These smaller volumes were found in all brain regions, but were significantly smaller in gray matter compared with white matter regions.
Higher evening cortisol was also tied to poorer cognitive functioning across all domains. In contrast, higher levels of morning cortisol were associated with slightly greater normal white matter volume and better processing speed and executive functioning, but were not associated with memory performance.
“Understanding these differential associations may aid in developing strategies to reduce the effects of hypothalamic-pituitary-adrenal axis dysfunction on late-life cognitive impairment,” the researchers wrote.