A Question

I sit a lot. I am sitting as I write this, you might even be sitting as your read this. There is also a good chance you sit lot throughout the day, especially if you are a student. I take stretch breaks, I used the standing workstations in the library and I do everything else I can do to reduce my sitting because somewhere along the line I got the impression that sitting is dangerous. Maybe it was the lecture I sat through in PT school about how intradiscal pressure is higher in sitting than in lifting1 and sitting is associated with weakened posterior lumbar structures2.  Maybe it was the aching I felt during back to back days of 8 hour lectures. It is common sense that sitting causes back pain and I heard this in both the classroom and the clinic, but is this assertion based on scientific evidence? Is self-reported sedentary behavior an independent risk factor for low back pain?

Some Data

Chen et al tackled exactly this question with a systematic review published in the Internal Archives of Occupational and Environmental Health in 2009. After an exhaustive search of the scientific literature they found ten prospective cohort studies and five case control studies relevant to the question. The study populations were varied including schoolchildren, military personnel, nurses, working population, patients and one twin study. Only five of these studies started off with subjects who had no back pain at baseline and the others did not classify low back pain clearly or rule out serious pathology. Of the nine studies that investigated time spent sitting at work only one cohort study reported a positive association all of the others found no relationship. Of the five cohort studies investigating sedentary behavior during leisure time, only one low quality study found a positive association and the other four found none. The authors’ conclusion was that there is no evidence to support that sedentary behavior or prolonged sitting at home, at work or combined is a risk factor for low back pain.

My Application

This review is looking at back pain from a bird’s eye view and making a tall order. It is asking if people’sself-report of sedentary behavior is related to their perception of pain. We don’t know what postures and positions the subjects are assuming while being sedentary and we don’t know anything about their pain sensitivity or other lifestyle factors that influence pain. When the study is framed in this light it seems nearly impossible to find a relationship between such subjective independent and dependent variables. Indeed I probably would have written off report  if it weren’t for the fact that a similar systematic review reported the same finding3 and some other predictors of low back pain have been found using similar study designs.Things like job dissatisfaction, monotonous tasks, poor work relations, lack of social support in the workplace, demands, stress and perceived ability were all reported to correlate with back pain incidence in two recent systematic reviews. were associated with an increased occurrence of low back pain4,5.

So what do I think? Is sitting going to kill your back? I’m sticking to the evidence on this one saying that sitting by itself is not enough to cause back pain until proven otherwise. But a sudden increase in the amount of sitting, along with stressful psychosocial factors such as graduate school could be just the right combination to do the trick. How you are sitting probably matters as well, as another recent systematic review reported that the combination of sitting, awkward postures and whole body vibration increased risk of back pain by 4x⁶. This is bad news for dentists who have the first two risk factors and helicopter pilots who have all three.

The discrepancy between the mechanical properties of the lumbar spine and intervertebral discs and patients report of pain is large and well documented.Having a degenerated spine on MRI simply does not predict low back pain⁷. Spinal degeneration such as disc space narrowing, osteophyte formation and even disc herniation have no correlation with patient symptoms. If back pain were mostly a mechanical problem, one of these things would correlate, but as it stands back pain is a human experience that influenced greatly by psychosocial factors both for better and for worse.

I am not proposing that we go on being as sedentary as possible, sitting on our way to work, sitting at work, sitting on our way back, sitting down for dinner, and sitting to read a book afterwards, because sedentary behavior is a well-documented risk factor for chronic disease. What I am saying is, don’t worry that sitting is going to give you back pain, because it is very likely that this worrying is more dangerous than the sitting itself.

References

1. Nachemson A (1966) The load on lumbar disks in different positions

of the body. ClinOrthopRelat Res 45:107–122.

1. Beach TA, Parkinson RJ, Stothart JP, Callaghan JP (2005) EVects of

prolonged sitting on the passive XexionstiVness of the in vivo

lumbar spine. Spine J 5:145–154.

1. Bakker EWP, Verhagen AP, van Trijffel E, Lucas C, Koes BW. Spinal mechanical load as a risk factor for low back pain: A systematic review of prospective cohort studies. Spine. 2009;34(8):E281.
   1.  W.E. Hoogendoorn, M.N. van Poppel and P.M. Bongers, et al. Systematic review of psychosocial factors at work and private life as risk factors for back pain. Spine,  25 16 (2000 Aug 15), pp. 2114–2125. | View Record in Scopus | | Full Text via CrossRef | Cited By in Scopus (315)
   2. S.J. Linton, Occupational psychological factors increase the risk for back pain: a systematic review. Journal of Occupational Rehabilitation,  11 1 (2001 Mar), pp. 53–66. | View Record in Scopus | | Full Text via CrossRef | Cited By in Scopus (103)
   3. Lis AM, Black KM, Korn H, Nordin M. Association between sitting and occupational LBP. European Spine Journal. 2007;16(2):283-298.
   4. Jarvik JG, Hollingworth W, Heagerty PJ, et al.Three-year incidence of low back pain in an initiallyasymptomatic cohort: clinical and imaging riskfactors. Spine 2005 ; 30 : 1541 – 8 .