Stress undercuts flu shots.

The strain of looking after a loved one with a protracted, debilitating illness can impair an elderly caregiver's immunity, a new study indicates. John Sheridan of the Ohio State University College of Dentistry in Columbus administered flu shots to 64 elderly men and women. Half had been caring for a spouse with Alzheimer's disease or some other form of progressive dementia for about 7 years.

"When you vaccinate somebody, you generally want to see a fourfold increase in the antibodies they have," Sheridan notes. But only about 37 percent of the caregivers mounted such a defense against flu viruses-roughly half the rate seen in the other participants. Several other measures of cellular and antibody-based immunity appeared to be similarly compromised, he and his colleagues report in the April 2 Proceedings of the National Academy of Sciences.

This is the first study to demonstrate significant stress-induced reductions in the apparent efficacy of an important vaccine among the elderly, he says. "If you're a caregiver and chronically stressed, make sure you get the vaccine every year," he recommends, because marginal responses to the vaccine often improve in succeeding years.

Outside pursuits and friends also help, adds psychologist Janice K. Kiecolt-Glaser of the Ohio State University College of Medicine in Columbus, who led the study. "We know from earlier work in our lab that caregivers who appear to fare best psychologically and immunologically are those who report greater social support and more satisfying social relationships."