Chronic stress in elderly carers of dementia patients and antibody response to influenza vaccination

Background There are many reports of psychological morbidity in spousal car ers of patients with dementia. The consequences of this increased stress on the immune system are unclear. We investigated whether antibody responses to influenza vaccination differed between carers and a control group, and t he relation of the antibody response to the hypothalamic-pituitary-adrenal (HPA) axis. Methods 50 spousal carers of dementia patients, median age 73 years (IQR 66 -77), and 67 controls (68 years [66-71]) of similar socioeconomic status we re enrolled. Anxiety and depression were measured by the Savage Aged Person ality Screening Scale and stress by the Global Measure of Perceived Stress scale. Principal-component analysis was used to yield a summary score of em otional distress from these two scales. Salivary cortisol concentrations we re measured over a single day at three times (0800-100, 1100-1300, and 2000 -2200). Participants received a trivalent influenza vaccine and IgG antibod y titres to each strain were measured on days 0, 7, 14, and 28. Findings Mean scores of emotional distress were significantly higher in car ers at each time point than in controls (all p < 0.0003). Mean (SD) salivar y cortisol concentrations, calculated as area under the curve (AUC), were h igher in carers than controls at all three assessments (6 months 16.0 [8.0] vs 11.2 [4.4], p = 0.0001; respectively). Eight (16%) of 50 carers and 26 (39%) of 67 controls had a four-fold increase in at least one of the IgG ti tres (p = 0.007). There was an inverse relation between AUC cortisol and Ig G antibody titre to the Nanchang strain that was significant on day 14 (r = -0.216, p = 0.039). Interpretation Elderly carers of spouses with dementia have increased activ ation of the hypothalamic-pituary-adrenal axis and a poor antibody response to influenza vaccine. Carers may be more vulnerable to infectious disease than the population of a similar age.