"Association of objective and subjective sleep duration and diurnal cortisol rhythm among community-dwelling people living with cognitive impairment".

Both short and long sleep durations negatively impact cognitive health in older adults, with changes in sleep linked to disruptions in the hypothalamic-pituitary-adrenal (HPA) axis. However, research on the relationship between sleep duration and diurnal cortisol rhythm in cognitively impaired individuals is limited. This study investigates the association between objective and subjective sleep duration and cortisol rhythm indicators in 195 cognitively impaired population. Participants provided saliva samples over two days, while sleep duration was collected by actigraphy and one PSQI item. Results revealed that 60 % of participants (objective) and 45 % (subjective) slept 7-8 h. Normal and long sleep durations were associated with a preserved diurnal cortisol rhythm. Short objective sleep duration was linked to higher waking cortisol in females and a diminished cortisol awakening response, while no significant effects were found with subjective sleep duration. This suggests that sleep normalization may help maintain healthy cortisol patterns in cognitively impaired individuals.