There's a commonly held belief that once you've had an episode of low back pain (LBP), you are liable to have another. Studies estimate that the recurrence rate for LBP can be as high as 84 per cent. But the authors of this study challenge that thinking. They point out how research in this area has been flawed.

There are three common errors in research that have led to an over estimate of LBP recurrence. First, patients included in the studies may not have recovered from the first episode of back pain before they had a second episode. Technically, they have not had a recurrence but rather, persistence of symptoms from the first episode.

Second, some patients recover from their first episode of back pain but not right away. Their recovery may take months instead of days or weeks. Recovery so late means they were at risk of recurrence for a very short amount of time. Using that approach results in misleading numbers of patients reported to have a recurrence of low back pain.

Third, the definition of an episode of back pain isn't always the same from one study to the next. This may be changing with some of the more recent studies as authors have become aware of the problem and are making efforts to use a more standardized definition.

The current definition proposed for future studies is as follows. An episode of low back pain is a period of pain in the lower back lasting for more than 24 hours. It is preceded by and followed by a period of at least one month without low back pain.

In this study, the authors estimate the one-year incidence of low back pain recurring in patients who had recently recovered from an episode of acute low back pain. They also tried to identify risk factors to help predict who might be likely to have a recurring episode in the next 12 months following the initial back pain episode.

Over 1,000 low back pain patients treated by general practitioners, physiotherapists, and chiropractors were included. The study took place in Australia where these three professional groups are largely responsible for the care of low back pain patients. Only patients with nonspecific acute low back pain were included. Nonspecific means the source was unknown but not from a fracture, infection, tumor, or other serious disease.

Data was collected from each patient about their general health, psychologic status, occupation, and sociodemographics (e.g., age, gender, education). Use of tobacco, activity levels, and previous episode(s) of low back pain were also noted. By collecting a wide range of information, they hoped to be able to sort through all the variables and find those factors that were statistically significant. Significant or predictive factors could help point to those patients likely to suffer a second or recurring episode of low back pain.

They were careful to only include patients who had low back pain lasting for more than 24 hours, less than six weeks, and who had recovered fully by the end of six weeks. Using these criteria, about one-third of the original 1,000 subjects were still left in the study.

The main measure was recurrence of low back pain. This was determined by asking patients to recall any episodes of back pain in the previous 12 months. They also had patients report their pain levels at the end of three- and 12-month periods of time.

The group reported a 24 to 33 per cent recurrence rate. This was much lower than the 47 to 84 per cent range reported by other researchers. The authors are quite certain that this difference was because they only used patients who had recovered from the first episode of pain. In this way, they avoided calling persistent symptoms or flare-ups as recurrent episodes.

A previous history of low back pain was the only factor that predicted a second episode. Patients with a prior episode of back pain were twice as likely to develop recurring symptoms as those who did not have a previous history of back pain. This was true no matter how old (or young) the person was at the time of the first episode.

The authors point out that the recurrence rate from their study was much lower than in previously published reports. Further analysis of their data also revealed that those patients who were worried about a future episode of back pain were more likely to have a second or recurring episode. This predictive factor is called perceived risk of persistent pain. It was determined through patient opinion of the risk of persistent pain self-rated from zero (no risk) to 10 (high risk).

They conclude that more accurate estimates of recurrence of low back pain than are currently available are possible. Definitions of pain episodes, recovery, and recurrence and methods of measuring these variables are important. These definitions must make it possible to determine when a new episode of back pain is occurring versus when a flare-up of the old episode is present.

Patients should not be allowed to define what recurrence means for themselves. With proper selection, researchers can restrict studies of this type to patients or subjects who have fully recovered and are therefore truly at risk for recurrence. In this way, a more realistic incidence of recurrence can be reported.

The annual worldwide cost of caring for people with episodes of acute low back pain is in the billions (90.8 billion in the United States alone). Predicting future episodes of low back pain as a means of possibly preventing further problems is a valuable tool. Although difficult to predict, doing so could potentially reduce the cost of medical care through prevention.

Future studies are needed to find out if the number of previous episodes of low back pain is important. If so, how many previous episodes are significant? Finding modifiable risk factors that can then be changed is another way to approach the problem of recurring low back pain. A good study design with standard definitions and time periods is advised. True recurrences should not be mixed up with flare-ups or persistent pain.

Tasha R. Stanton, MScRS, et al. After an Episode of Acute Low Back Pain, Reucrrence is Unpredictable and Not as Common as Previously Thought. In Spine. December 15, 2008. Vol. 33. No. 26. Pp. 2923-2928.