By Pat Anson, Editor

An important new study has confirmed that a patient’s genes really do play a role in determining whether they develop chronic pain after surgery.

Researchers in China collected blood samples from 1,152 surgical patients to look for genetic variations in 54 "pain-related" genes which have been associated with pain sensation. Patients were then contacted a year later to see if they had chronic post-surgical pain.

A surprising number – one out of five patients – still experienced pain at the wound site, and 33 percent of them said their pain was severe.  Patients with pain also reported problems with their overall health, as well as daily activities such as mood, walking, relations with others, sleep, and quality of life.

Aside from genetic factors, the study also found patients younger than 65, males, and those with a prior history of chronic pain were at increased risk. The study is published online in the journal Anesthesiology.

"Our study not only shows there are common genetic variations among people that may help to identify whether they are at high-risk for developing chronic pain after surgery, but it also helps explain why only a fraction of patients ever even experience persistent pain," said lead researcher Matthew T.V. Chan, MD, at the Chinese University of Hong Kong.

"Until now, the genetic variations associated with chronic post-surgical pain have not been well identified."

One genetic variation in particular - a gene found in the nervous-system called brain-derived neurotrophic factor (BDNF) - was found to be most frequently associated with chronic post-surgical pain. Researchers confirmed the finding in a study on laboratory mice.

The researchers also found that genetic variations account for a higher percentage of chronic post-surgical pain (between 7 percent and 12 percent) than other risk factors such as age, sex, smoking history or anesthesia technique (between 3 percent and 6 percent).

Chronic post-surgical pain is one of the most common and serious complications after surgery. Previous studies have found that chronic pain was common after abdominal hysterectomies (25.1%) and heart or lung surgery (37.6%).

“Considering that more than 230 million surgeries are performed each year worldwide, the data would imply that millions of patients will continue to suffer wound pain, months to years after their surgery,” researchers said.

The study comes at a time when many U.S. states have adopted or are enacting laws that would limit the supply of opioid medication to just a few days for acute short-term pain. Minnesota, for example, is close to adopting strict guidelines that would limit the dose and supply of opioids to three days for acute pain and seven days after a major surgery.