Elderly spouses who care for demented patients undergo substantial physical and psychologic stress. Several studies have documented increased morbidity in these spouses and have suggested a link to depressed immune function. Vedhara and colleagues studied the association between stress levels and immune function in caretakers of demented patients.

Fifty spousal caretakers of demented patients were recruited for the study and matched by age, sex and socioeconomic status with 67 control subjects. None of the study participants had a terminal illness and none was receiving drugs that could affect the immune system. All participants were assessed with the use of a battery of psychologic tests and all provided samples for estimation of cortisol and influenza IgG antibodies at baseline, three months and six months. At the six-month follow-up, trivalent influenza immunization was given to the study participants. Blood samples were taken to estimate IgG antibody response to each of the three vaccine components at seven, 14 and 28 days after immunization.

Throughout the study, scores of emotional distress levels and cortisol levels were significantly higher for the caretakers than for the control subjects. At baseline, caretakers and control subjects did not differ in concentrations of antibodies to any of the influenza vaccine components. Following immunization, 26 of the control subjects (39 percent) had a positive response to at least one of the vaccine components, compared with only eight of the caretakers (16 percent). This difference was statistically significant. The vaccine contained three components, two of which had been included in the influenza vaccination offered in the previous year. The IgG response of caretakers to the new strain was significantly poorer than that of the control subjects, suggesting an association between chronic stress and poor immune function.

The authors conclude that elderly caretakers of demented spouses reported increased levels of distress and showed increased activation of the hypothalamic-pituitary-adrenal axis. One measurable outcome was poor antibody response to influenza vaccine, leaving caretakers more vulnerable to influenza infection despite immunization.