Older people are particularly exposed to stressful events, known to activate the hypothalamus-pituitary-adrenal axis. Many studies highlighted the possible deleterious effects of elevated cortisol on cognition, assuming a likely role of stressful events. Yet, very few studies actually examined these assumed links between life events, cortisol and cognition.

To examine associations between salivary cortisol, cognition and life events in a population of non-demented old individuals.

A cross-sectional analysis was conducted using data from Colaus/PsyColaus, a longitudinal population-based study involving 6733 Lausanne residents. Salivary cortisol samples (upon waking, 30 minutes after waking, at 11 am and at 8 pm) were obtained from 799 non-demented participants aged at least 60.

Life events, activities of daily life along with depressive symptoms were assessed using a standardized questionnaire. A comprehensive neuropsychological test battery was used to determine the Clinical Dementia Rating (CDR).

For multiple comparisons, P values were adjusted (P′) according to Holm-Bonferroni's method.

Cortisol at 11 am and cortisol area under the curve (AUC) were positively correlated with CDR sum of boxes (CDRSOB) scores (P′ = 0.035; Rho = 0.097 and P′ = 0.024; Rho = 0.110, respectively). The association between cortisol AUC and CDRSOB remained significant after controlling for age, sex, body mass index, education, smoking and depression (P = 0.001; β = 0.001; R2 change = 0.016).

The number and the total impact of life events were associated neither with cortisol nor with CDRSOB.

Elevated cortisol was associated with poorer cognitive functioning yet independently of life events. This suggests that the increased cortisol associated with poorer cognition might be not a mere reflection of stressful events but rather explained by other factors, yet to be elucidated.

The authors have not supplied their declaration of competing interest.