Back pain trajectories
How does chronic back pain tend to work out? Spoiler alert: Pain has a nasty habit of continuing in the same general direction. 😕
Just a quick science-summarizing post today. My week has mostly been spent on projects too big for blogging. Remember, when I’m not putting things in your inbox, it’s because I’m working on books! And articles as big as small books! But I’d like to share a little excerpt from one of my works-in-progress. Recently I wrote:
“The average duration of an acute episode of back pain is pretty well-pinned down. We know that most cases resolve, rather than becoming chronic, and that most chronic cases are only chronic for several months (not years).”
A respected reader asked me to reconsider that. Is it really most? There’s a case to be made, and I was mainly thinking of research I explore in detail here, which certainly has a bright side. But I’ve been digging into the question of just how well back pain goes for people, so I’d like to tell you about a pair of thought-provoking prognosis papers…
Way back in the mid 2000s, twenty years ago, Dunn et al. followed many dozens of people for a year, and classified their back pain into four “trajectories”:
- persistent mild (stable, low levels of pain)
- recovering (started with mild pain, progressing quickly to no pain)
- severe (permanently high pain)
- fluctuating (pain varied between mild and high levels)
Once that was established, they were followed for five years. And then, several years later in 2018, Chen et al. finally reported what they learned from that following. How did things go for those patients?
They were quite likely to be on the same trajectory five years later, for better or worse. For instance, if their original trajectory was “persistent mild,” then it was likely to still be “persistent mild” five whole years later.
In fact, the odds of trajectory consistency were “very high,” greater than 90% for persistent mild, recovering, severe; and 74% for fluctuating. (Specifically, the paper reports the “posterior probability for the assigned clusters.” Posterior probability is, roughly, “the odds in retrospect, given what we know now.” And now I will get objections from my statistically savvy readers in three, two, one….)
Also, several factors were “significantly” linked to worsening over five years: severity, poverty, and “several dimensions of perception,” such as pessimism and passivity.
The design of all this research was generally great — the power of a prospective trial, of following people over time — but no study can do everything, and it is important to note that this was a study of people who already had some kind of chronic back pain. So this is definitely not a study of “how likely is back pain to become chronic,” but rather “how likely is chronic back pain to drag on.” As the authors acknowledge, the results could be quite different “in other groups of patients with pain, for example, patients with new episodes of back pain, pain in other body sites, or different age groups.”
So that’s one piece in this puzzle. This research contradicts my claim most chronic cases are only chronic for several months (not years), but there’s still more to the story, and I will continue to pick away at this question. Stay tuned.
