What's more, those who had reported especially high levels of pain and stress were the ones most likely to become sick later.

This study is one of the first to suggest a strong link between short-term pain and immune system change and subsequent health problems such as upper respiratory illnesses or increased pain.

The findings will serve as a basis for further studies on the effects of stress and pain on immune function, an area of research with implications for an assortment of other anxiety-inducing procedures such as angioplasty and colon exams.

"It is significant that the people in the study were healthy to begin with and experienced these short-term decrements in immune functions," said Henrietta L. Logan, the study's principal investigator who serves as director of the UF College of Dentistry division of public health and research. "We now need more research on nonpharmacological interventions prior to these procedures that will help lessen patients' stress and anxiety and improve recovery."

Some interventions that can be explored include relaxation therapy, guided imagery or hypnosis, said Logan, also a professor in the college's department of operative dentistry.

"Relaxation and deep breathing are two relatively easy strategies that patients may find useful in coping with stressful procedures," Logan said. "Imagery, relaxation training and hypnosis have been used successfully to treat acute procedure pain."

Finding a way to decrease pain and stress may prove particularly important in patients who may have decreased immune functions to begin with, such as the elderly or people with cancer or AIDS.

"Symptoms of cold and flu may not seriously harm a healthy patient, but it may lead to more serious consequences for patients with decreased immunity," Logan said.

In designing the study, the researchers' goal was to determine whether pain and stress associated with a common dental or medical procedure would affect measures of immune function and later development of upper respiratory illness symptoms.

The researchers chose root canal therapy solely as a model of a common procedure that typically yields stress and pain for a patient, Logan said.

For the study, the researchers recruited 33 healthy patients who had root canals scheduled at a University of Iowa dental clinic. Fourteen other patients were recruited to form a control group.

The researchers tested blood samples from the patients before, during and after root canal treatment to measure levels of cortisol, a stress hormone, and the activity of "natural killer cells," which play an important role in guarding the body against infection. Participants in the control group also were tested over a similar course of time.

Study participants were given questionnaires and diaries to record the level of pain and stress they experienced and any signs of illness. They also indicated their pain and stress levels on a rating scale at two and six hours following treatment, with corresponding times for the control group.

The results showed a significant difference between dental patients and the comparison group in the number of self-reported illness symptoms in the period after treatment. Thirteen of the dental patients developed an illness during the second week after treatment compared with two in the control group.

Among the root canal patients, the data also showed that it was those who later developed an illness who had reported higher levels of pain in the hours after the procedure. Additionally, those who became ill had lower natural killer-cell activity 30 minutes after the treatment than those who had remained healthy. Cortisol levels were higher at the final blood draw among those who were ill than among those who were not. It is probable that these changes were a result of the treatment, the stress of the dental injection and the short-term effect of the anesthetic, Logan said.

"Dr. Logan and her colleagues have shown that stress, pain and immune function are critical factors closely linked to the vulnerability of patients to subsequent illness," said Dr. Robert P. Yezierski, director of the UF Center for Pain Research affiliated with the Evelyn F. and William L. McKnight Brain Institute of UF. "The study suggests that for the general well-being of the patient, we should consider using a more comprehensive strategy of patient care designed to address the risk factors of stress and pain and their impact on long-term health complications."

Further research will be needed to assess how quickly people recover after a stressful and painful dental or medical procedure and how these short-term immune changes affect overall health.

This should include investigating whether people whose immune system takes longer to recover are more at risk for health problems than those who recover more quickly, Logan said.

The study was sponsored by a grant from the Fetzer Institute in Kalamazoo, Mich. - By Tracy Brown and Connie Daughtry

25-May-2001