From Stress Titers to Influenza Titers: Big Leap for Little Gain
August 1999; Volume 1: 72
Source: Vedhara, et al. Chronic stress in elderly carers of dementia patients and antibody response to influenza vaccination. Lancet 1999; 353:627-631.
Design and Setting: A controlled study of 50 spousal carers (carer is British for caregiver) of dementia patients and 67 controls matched for socioeconomic status. The carer group (including 26 women) served as primary caregivers; cared for their partners at home; and reported no other caregiving responsibilities.
The 67 controls (including 36 women) had living partners without dementia, and they themselves had no caregiving responsibilities for others. None of the carers or controls had end-stage illnesses, and none were receiving treatment, e.g., glucocorticoids or immunosuppressant drugs, that could interfere with cortisol levels or antibody response.
The median age was slightly higher for carers than for controls (73 vs. 68), and the median income somewhat lower (£14,007 vs. £14,128). Both groups had comparable rates of chronic illness.
Methods: All participants were seen at baseline, three months, and six months. At each visit psychosocial assessments were detailed with elaborate standardized screens. Endocrine assessment was measured at three specified times on one day via cortisol levels in saliva samples. At six months all participants received the 1997/98 trivalent influenza vaccine. IgG antibody response to each of the three influenza strains (Harbin, Nanchang, and Johannesburg) was measured prior to the vaccine on day 0 and on days 7, 14, and 28.
Results: Both the mean scores of emotional distress and the mean cortisol levels were significantly higher in carers than controls at each point before vaccination. Eight (16%) of the carers and 26 (39%) of the controls were "vaccine responders" (defined as those who had a positive response to at least one of the vaccine components). However, the "null responders" (defined as those whose day 0 antibody concentrations to the three strains were equal to or greater than the positive levels for the antibody test method) were a larger group: Harbin, 19 carers, 19 controls; Nanchang, 16 carers, 9 controls; and Johannesburg, 13 carers, 9 controls.
Funding: British Neuroendocrinology Charitable Trust.
Comments: This interdisciplinary study with each discipline contributing a complex component unfortunately does not add up to a significant result, i.e., three mountains moved to create one molehill. We already know that caregivers experience significant stress, and that stress can raise cortisol levels. Also, we know that cortisol can interfere with immune function. But in this study, about 40% of the carers and controls were already immune to at least one of the influenza strains that was used to measure immunity.
My vote: Back to the drawing board for this research group with an assignment to find more substantial results to back their opening claim that "Elderly carers of spouse have increased activation of the hypothalamic-pituitary axis and a poor antibody response to influenza vaccine." (Show us next time!)
August 1999; Volume 1: 72
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