This study was performed to determine the relationships between chronic pain and anatomic changes that may occur in the body. Autopsies were performed on fatalities that required death investigation in Linn County, IA, or adjacent and nearby areas.

Persons with chronic pain were older than the control population at the time of death. Diabetes, hypertension, and depression were more common in persons with chronic pain. Certain causes of death may also have been related to chronic pain.

The heart, lungs, liver, spleen, and kidneys were significantly heavier in persons with chronic pain; emphysema and pleural and abdominal adhesions were more common in persons with chronic pain.

There appear to have been diffuse changes in the body related to chronic pain. These changes may have been mediated by several systemic mechanisms that are involved with chronic pain, including cardiovascular activity, the immune system, the neuroendocrine system, and others.

Other anatomic differences may also suggest a reaction to chronic pain. For example, the surgical absence of the gallbladders and appendixes in persons with chronic pain suggests that these persons may be more alert to the experience of pain in general, leading to surgical intervention more frequently when the subjects observed abdominal pain compared to the control population.

The significant incidence of pneumonia in persons with chronic pain could be related to decreased mobility in persons who experience ongoing pain, or the higher incidence of emphysema that was found in the pain group.

Adhesions were more common in the pleural and abdominal cavities of the pain group, suggesting systemic inflammation. Conversely, there was no increased incidence of cerebral edema, atherosclerotic cardiovascular disease, myocardial infarction, steatosis cirrhosis or hepatitis.

Clinically, the concurrence of depression and chronic pain is well known. The cause of death in persons with chronic pain was significantly more likely to have been due to toxicological causes compared to controls.

Drug interactions

The greater use of opioid, antidepressant and sedative medications by persons with chronic pain, as well as the increased incidence of substance abuse, might increase the risk of fatalities from drug interactions.

Also, access to these medications in the context of ongoing distress and increased clinical depression could be related to suicide in this group, although the incidence was not significantly increased in this study. Fatalities from accidental overdoses and drug interactions were significantly higher than the control population, however.

The anatomic changes with the corresponding clinical or demographic correlations found in this study suggest that differences in the body are possibly correlated with chronic pain in many ways, such as organ enlargement, pneumonia, depression and increased likelihood of abdominal surgery such as cholecystectomy and appendectomy.

The causes of death appear to demonstrate an increased risk of death from pneumonia or toxicological causes in persons with chronic pain. The mechanisms of these changes are complex and may include multiple factors.