Short objective sleep duration was linked to higher waking cortisol in females and a diminished cortisol awakening response, while normal and long sleep durations were associated with a preserved diurnal cortisol rhythm in cognitively impaired individuals.
Key Findings
Results
The majority of cognitively impaired participants slept 7-8 hours, though objective and subjective measures yielded different proportions.
Study sample consisted of 195 community-dwelling people living with cognitive impairment.
60% of participants met the 7-8 hour sleep duration threshold based on objective actigraphy measurement.
45% of participants met the 7-8 hour sleep duration threshold based on subjective report (one PSQI item).
Sleep duration was collected using both actigraphy and one item from the Pittsburgh Sleep Quality Index (PSQI).
Results
Normal and long sleep durations were associated with a preserved diurnal cortisol rhythm in cognitively impaired individuals.
Saliva samples were collected over two days to assess diurnal cortisol rhythm indicators.
Both normal (7-8 hours) and long sleep durations were linked to maintenance of healthy cortisol patterns.
The hypothalamic-pituitary-adrenal (HPA) axis was the proposed biological mechanism linking sleep and cortisol patterns.
This finding applied to the cognitively impaired population studied.
Results
Short objective sleep duration was associated with higher waking cortisol levels specifically in female participants.
The association between short sleep duration and elevated waking cortisol was sex-specific, observed only in females.
No significant effect of short subjective sleep duration on waking cortisol was found.
This sex difference suggests differential HPA axis sensitivity to sleep disruption between males and females with cognitive impairment.
Objective sleep duration was measured via actigraphy.
Results
Short objective sleep duration was linked to a diminished cortisol awakening response in cognitively impaired individuals.
The cortisol awakening response (CAR) was one of the diurnal cortisol rhythm indicators assessed.
Short objective sleep duration was associated with a blunted or diminished CAR.
No significant effects on the cortisol awakening response were found with subjective sleep duration.
Saliva samples were collected over two days to capture cortisol awakening response.
Results
Objective and subjective sleep duration measures showed discordant associations with cortisol rhythm indicators in cognitively impaired individuals.
Significant associations between short sleep duration and cortisol outcomes were found only with objective (actigraphy) measurement, not subjective (PSQI) measurement.
No significant effects were found with subjective sleep duration for any cortisol outcome examined.
The discrepancy between objective (60% normal sleep) and subjective (45% normal sleep) rates suggests limited accuracy of self-reported sleep in this population.
Cognitive impairment may reduce the reliability of self-reported sleep measures.
Background
Research on the relationship between sleep duration and diurnal cortisol rhythm in cognitively impaired individuals was identified as limited prior to this study.
Both short and long sleep durations are known to negatively impact cognitive health in older adults.
Changes in sleep are linked to disruptions in the hypothalamic-pituitary-adrenal (HPA) axis.
The study addresses a gap in the literature by focusing specifically on a cognitively impaired community-dwelling population.
The study included 195 participants with cognitive impairment.
What This Means
This research examined how the amount of sleep a person gets relates to their body's stress hormone (cortisol) patterns in older adults who have some degree of cognitive impairment, such as dementia or mild cognitive impairment. The researchers measured sleep in two ways — using wrist-worn activity monitors (actigraphy) that objectively track sleep, and by asking participants how long they slept (self-report). They also collected saliva samples over two days to measure cortisol levels throughout the day, including right after waking up.
The study found that when sleep was measured objectively, getting too little sleep was associated with disrupted cortisol patterns — specifically, higher cortisol levels right after waking in women, and a weaker 'cortisol awakening response' (a normal morning spike in cortisol that helps the body prepare for the day). In contrast, getting a normal amount (7-8 hours) or even longer sleep was linked to healthier, more typical cortisol rhythms. Interestingly, self-reported sleep duration did not show these same associations, suggesting that people with cognitive impairment may not accurately recall or perceive how long they actually sleep.
This research suggests that maintaining healthy sleep duration may help preserve normal stress hormone functioning in people with cognitive impairment, and that women with cognitive impairment who sleep too little may be particularly vulnerable to stress system disruption. The findings also highlight that objective sleep measurement tools may be more reliable than self-report in this population, which has practical implications for how sleep is assessed and monitored in clinical and research settings for cognitively impaired individuals.
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Dong F, McPhillips M, Hodgson N. (2026). "Association of objective and subjective sleep duration and diurnal cortisol rhythm among community-dwelling people living with cognitive impairment".. Geriatric nursing (New York, N.Y.). https://doi.org/10.1016/j.gerinurse.2026.103999