Lee J, Gilligan M, Skoblow HF, Huo M, Ogle DM, Killoren SE. Hair Cortisol Concentration among Siblings Caring for a Parent with Dementia: A Dyadic Approach to Sibling Relationship Quality and Perceived Caregiving Stress. Biopsychosoc Sci Med. 2026 Jul 20. doi: 10.1097/PSY.0000000000001511. Epub ahead of print. PMID: 42476126.
A vast number of caregivers for individuals with Alzheimer's disease are adult children.
While both family members and non-family members may care for an individual with
dementia, adult child caregivers are often doing so alongside their siblings. The
relationship between siblings caring for their parent with Alzheimer's brings about unique
interactions and perceptions that may impact caregiver stress. This study examines how
sibling relationships, caregiving stress, and biological measures of stress, like cortisol
concentration in hair, aBect the caregiving experience of siblings caring for a parent with
dementia. Researchers hypothesized that sibling closeness, tension, and ambivalence
would be associated with hair cortisol concentration levels. The researchers expected
greater perceived caregiving stress to be associated with higher levels of hair cortisol.
This study used data from 66 adult (18+) sibling pairs, or dyads. 92% of participants were
White, and 82% of sibling pairs consisted of two sisters. Additionally, 91% of the
participants were women, and the average age of participants was 56.5 years. Data was
collected on sibling relationship quality, perceived caregiving stress, and hair cortisol
concentration. Sibling interactions in a caregiving environment may influence factors such
as cortisol production. Using hair samples to measure cortisol provides a stable method of
assessment for physiological eBects of stress.
Researchers found that when one caregiver felt greater closeness to their sibling, they
showed higher levels of hair cortisol concentration. When one sibling reported greater
emotional stress related to caregiving, the other sibling had higher levels of hair cortisol.
Higher cortisol concentration was reported alongside greater closeness between siblings
overall. One possibility is that being emotionally close to a sibling while caring for a parent
may involve taking on some of the sibling's emotional stress as well. However, high levels of
hair cortisol concentration do not necessarily mean an individual is more stressed. Rather,
stress may be shared between siblings instead of being caused by one another.
When one caregiver felt greater ambivalence (i.e. mixed or contradictory internal feelings)
toward their sibling, they showed lower levels of hair cortisol concentration. This finding is
unexpected and suggests that ambivalence may point to a possible protective role against
caregiving stressors. However, more research is needed on this relationship. Because
ambivalence is experienced internally, it is a possibility that their sibling is not directly
experiencing higher stress from the ambivalent caregiver. Authors suggest separating the
internal and external workings of caregiver stress in future research. The study’s findings
may indicate that stress could be influenced by the perception and share of responsibility
among siblings.
The findings of this study reveal unique associations between siblings at the familial level,
while highlighting the stress and relationship quality that influence the interdependence of
the caregiving experience. Within the research surrounding the health of adult child
caregivers of parents with dementia, sibling pairs have received limited attention as a
population of interest. This study adds to current research by focusing on sibling pairs and
by assessing hair cortisol concentration within the pairs. This study introduces and
expands on the development of interventions to reduce caregiver stress.