The informal caregiver group consisted of 60 caregivers of individuals with cancer. Recruitment efforts included in-person requests at the Bone Marrow Unit of a local hospital (62.9%, n=44), email invitations to a local cancer support organization (20%, n=14) and members of a caregiver support group at a local cancer center (12.9%, n=9), and listserv announcements to a university community (4.3%, n=3). Caregivers identified as a partner (51.7%, n=31), parent (15%, n=9), child (13.3%, n=8), sibling (5%, n=3), friend (3.3%, n=2), or ‘other’ (8.3%, n=5) with regard to their relationship with the care recipient. The remaining two caregivers (3.3%) did not specify their relationship to the cancer patient. Caregivers identified the cancer type of the care recipient as lymphoma/leukemia (30%, n=18), brain (10%, n=6), breast (11.7%, n=7), colorectal (11.7%, n=7), lung (8.3%, n=5), and other (e.g., bladder, skin, myeloma; 25%, n=15). The remaining two caregivers (3.3%) did not specify the type of cancer the care recipient had. Caregivers provided care for one week to up to 264 months, with a median of 12 months, and the number of hours per week of care ranged from about one hour to 168 hours within a week, with a median of 27.5 hours per week.
The mean age of the informal caregiver group was 51.17 (SD of 15.22, range of 19 to 77). Regarding gender, 71.7% (n=43) of caregivers identified as female, and the racial/ethnic composition of the caregiver sample included 53 White (88.3%) four Black (6.7%), two multiracial (3.3%), and one Asian (1.7%) caregiver. The caregivers were primarily married (63.3%, n=38), with others identifying as single (16.7%, n=10), divorced (10%, n=6), living in a stable relationship (5%, n=3), widowed (3.3%, n=2), and being separated. (1.7%, n=1). Further caregivers reported to have <$35,000 (33.3%, n=20), had $35,001 to $50,000 (18.3%, n=11), $50,001 to $100,000 (26.7%, n=16), had >$100,000 (18.3%, n=11) annual income, and two chose not to answer (3.3%).
The 46 non-caregiver control group participants were recruited using listserv announcements to a university community. The mean age of this group was 36.61 (SD of 12.80, range of 22 to 66). Regarding gender, 95.7% (n=44) of the control group identified as female, and the racial/ethnic composition of this sample included 45 White (97.8%) and one multiracial (3.3%) caregiver. The control group participants were primarily married (50%, n=23) with others identifying as single (32.6%, n=15), divorced (6.5%, n=3), living in a stable relationship (4.3%, n=2), widowed (2.2%, n=1), and two chose not to answer (4.3%). Further, non-caregivers reported to have <$35,000 (17.3%, n=8), $35,001 to $50,000 (13%, n=6), $50,001 to $100,000 (50%, n=23), >$100,000 (18.3%, n=7) annual income and two chose not to answer (4.3%).
No significant differences between the informal caregiver group and the non-caregiver control group were found for race/ethnicity, χ²(3) = 4.21, p = .240, and income, χ²(7) = 11.84, p = .106. However, the caregivers were significantly older, t(104) = 5.22, p < .001, and more likely female, χ²(1) = 10.18, p = .001.
The current study is a cross-sectional examination of informal cancer caregiver stress, NAS, depressive symptoms, and salivary cortisol and is part of a larger study (for other relevant publications, see BLINDED). The study was approved by the University of BLINDED Institutional Review Board (IRB NUMBER: 13.0135) and informed consent was obtained from all participants; surveys were completed using an online program or on paper. Data from informal caregivers were collected at the local hospital and during meetings of cancer caregiver support groups. The non-caregiver control group completed the study visit on the university campus.
Demographics. Self-reports of gender, weight, height, birthdate, socioeconomic status, and race/ethnicity were collected. Variables relevant for physiological measurement (e.g., allergies, date of last period, gum bleeding, smoking, shift work, time of most recent food, fluid, and other substances) were recorded.
Negative Attribution Style (NAS). To measure the NAS, participants were presented with a hypothetical event (i.e., a caregiving situation for the informal caregivers and a non-caregiving situation for the non-caregivers) and asked to write down one cause for the event. Participants then rate the degree to which the cause of the hypothetical event is (a) internal, (b) stable, and (c) global. Each rating uses a 7-point Likert scale, with higher scores representing a more NAS. Consistent with previous research measuring NAS, the internal consistency in the current study was α = .60. This internal consistency is good considering that NAS is measured with only three items. Other instruments measuring NAS show similar internal consistency (36 items, α = .72; 25). Using the Spearman-Brown Formula, the instrument used in our study would have an internal consistency of α = .94 if it would have the same length.
Depressive Symptoms. The 20-item Center for Epidemiologic Studies – Depression Scale (CES-D) measures depressive symptoms over the past week . The Cronbach´s alpha of the CES-D in a previous caregiver study was α = .90 , which is consistent with the internal consistency in the current study (α = .91).
Cortisol. Saliva samples were collected between 4:00 PM and 6:00 PM. The passive drooling method was used for collecting a single whole saliva sample over a period of 5 minutes while the participants responded to the survey questions. Saliva was collected in Salivette sampling devices (Sarstedt, Rommelsdorf, Germany) and kept frozen until it was analyzed. Salivary cortisol was measured using the Salivary Cortisol ELISA kit (Salimetrics, Carlsbad, CA). The assay is based on a competitive electrochemiluminescence immunoassay (ELISA) method. The minimal detectable concentration of the method is 0.007 ug/dL. The intra- and inter-assay coefficient of variations are 3-7% and 3-11%, respectively.
Before testing the proposed hypotheses, we z-transformed the NAS scores and calculated the group (cancer caregiver = 1 vs. non-caregiver participants = 0) by z-transformed NAS scores interaction scores. Using these scores as predictors, we conducted two linear regression models with depressive symptoms and cortisol as outcome variables, respectively. None of the above listed health variables that have been to contribute to cortisol levels (e.g., allergies, caffeine, date of last period, gum bleeding, hormones, shift work, smoking) in the literature were significant in our sample. Because age and gender were significantly different between informal caregivers and non-caregiver control participants, we included those variables as covariates in both regression models. Control variables were entered in step 1 of the regressions. In step 2, the main effects of group and z-transformed NAS scores were entered as predictors. In step 3, the group by z-transformed NAS scores interaction was entered. To further examine significant group by attribution interaction effects, we constructed model-implied graphs.