Modeling cortisol daily rhythms of family caregivers of individuals with dementia: Daily stressors and adult day services use

Author(s): Liu, Y., Almeida, D.M., Rovine, M.J., and Zarit, S.

Published In: J Gerontol B Psychol Sci Soc Sci, 73 (3): 457-467

Study Aim/Purpose: This study examined associations between the timing of adult day service (ADS) use and the trajectory of daily cortisol levels as a biomarker for stress among caregivers of individuals with dementia who experience chronic stress. 

Summary of Methods: The study involved 165 family caregivers who live in the same household and care for individuals with dementia and use ADS programs at least two days per week. Each participant had an initial interview to collect background information. The caregivers were also asked to complete a daily diary. Daily evening interviews collected information compiled in those diaries on daily ADS use that day, care-related stressors, non-care stressors and positive events of each day as well as caregivers’ daily sleep quality, duration and wake up time. They also were asked to collect five saliva samples a day to measure their daily cortisol trajectory. The authors tracked the caregivers’ cortisol levels in relation to the timing of receipt of ADS and examined other covariates to determine if these mediated the impact of ADS use. 

Summary of Results: Stressor exposures among caregivers of individuals with dementia were associated on a daily level with increased cortisol levels before bed. Additionally, daily ADS use was associated with a more robust cortisol awakening response and a steeper decline in cortisol starting from 30 minutes after waking, which can benefit a person under chronic stress. On non-ADS use days, however, caregivers tended to have a flatter diurnal patter of cortisol levels. Additionally, more ADS use days were associated with a slight but significant increase in cortisol later in the day. Controlling for caregiver characteristics, such as age, gender, and duration of care, all significant positive ADS effects on the caregiver’s diurnal cortisol levels remained. Additionally, ADS use had a significant positive effect on the diurnal cortisol slope when the covariates of stressors or positive experiences were controlled for at both the daily and person levels. 

Study Limitations (as cited by authors): Authors pointed out that the fixed time windows for salivary samplings did not allow for aligning the timing of stressor exposure to cortisol diurnal rhythms. Additionally, the relatively demanding nature of the data collection meant that the respondents were not likely typical of the broader population of family caregivers of individuals with dementia and thus the findings not generalizable. 

Authors’ Discussion/Conclusions: The authors highlight the findings associating a more robust CAR slope with days of ADS use days as a biomarker indicating that ADS use provides caregivers partial relief from the primary stressors of care receivers’ behavior problems. The authors suggest that future studies examine the effects of a longer time period of ADS use on the cortisol awakening response and the initial morning decline of cortisol as well as on other daily biomarkers of the stress response and long-term health.