There is no evidence that general employment in the military, police, fire services, healthcare or the majority of occupations leads to an increase in degenerative changes in the spine. This is probably because the amount of time spent undertaking heavy manual activity is relatively small. There is strong evidence against an association between back pain and most of the normal activities military personnel, police and firefighters would undertake (Kwon et al., 2011). A study of US urban firefighters found 80 % had reported neck, back or shoulder pain and this was negatively correlated with frequency of aerobic exercise (Beaton et al., 2002).
The legal concept of causation differs from the scientific concept and is a particularly challenging area in low back pain. Degeneration is an ongoing process, and a disc may inevitably have prolapsed at some point, so a particular activity on a particular day may seem irrelevant scientifically if it represents say 0.01% of lifetime forces on the spine. If, however, the 'final straw' was a particular work activity, it may be argued that legally this caused the disc prolapse. While it may be unlikely that a disc prolapse can be clearly attributed to one event at work, if it can, an argument may well be made that this is a 'qualifying injury' in relation to pensions, or justification for compensation. It is particularly important when taking a history at the time or shortly afterwards to identify all activities at or around the time of the alleged qualifying injury. Many military personnel, police and firefighters undertake other activities, or reservists may have other employment that may be much more physical than their military, police or firefighting role. The combination of unreliable memories and secondary gain should always be considered when taking a later history. Contemporaneous sources such as accident records and GP records should be considered before forming an opinion on causation.
There is evidence that significant acute injury to the spine may be caused by a specific incident at work, particularly when there is clear evidence of acute trauma at the time. An applicant in these circumstances would be expected to have attended for acute medical care either as a result of back pain or as a result of other trauma, with demonstrable signs and symptoms of an acute injury.
There is, however, evidence that moderate or mixed physical loading results in the least pathology to the spine; symmetric disc degeneration is associated with sedentary rather than active work, while vertebral osteophytes are related to heavy work. Back pain, rather than back pathology, is however related to more active work (Videman et al., 1990). There are many studies that demonstrate a clear link between physical workload, including frequent bending and twisting, and low back pain but there is no evidence in most studies linking this work to degenerative conditions in the spine.
One study in dock workers who are undergoing constant heavy manual work shows a link to degenerative conditions, although there is no evidence that a transfer to light duties slows the process of degenerative disease (Waskiewicz, 1996).
A recent review found no strong evidence supporting a causal relationship between any occupational physical activity considered and low back pain. A statistical association was found between low back pain and bending, twisting, lifting and pushing/pulling but not a causal link. Strong evidence against a causal relationship was found between low back pain and manual handling/assisting patients, awkward postures, carrying, sitting, standing and walking (Kwon et al., 2011).
A study of US urban firefighters found 80% had reported at least one neck, back or shoulder problem. Frequency of aerobic exercise was significantly and negatively correlated with complaints (Beaton et al., 2002). This suggests that regular aerobic exercise is protective.
A review of back pain in US military personnel found an increase associated with training and combat deployments. Three-quarters involved low back pain, followed by cervical and then mid-back symptoms. Predictive factors included psychosocial distress, heavy physical activity and more sedentary lifestyles. Specific military-related factors included g-force exposure in pilots and airmen, heavy combat load requirements and falls (Cohen et al., 2012).
On the other hand, a review of the US Defense Medical Epidemiology Database found significantly lower rates of acute low back pain in active duty infantrymen compared to matched controls, with significantly lower rates still in Marines versus the Army, and lower rates among junior enlisted compared to senior enlisted service members (Ernat et al., 2012).
Another US review, of active duty Marines deployed to Iraq or Kuwait between 2005 and 2008, found low back pain was more prevalent in non-infantry occupations, with the highest prevalence in construction (8.6%) and law enforcement (6.2%) subgroups. Overall incidence of low back pain was 4.1% of a total of 36,680 personnel (MacGregor et al., 2012).
A review of all active-duty US military service members between 1998 and 2006 found a small but statistically significantly increased rate of low back pain compared with matched control population (Knox et al., 2014).
It is not possible to determine whether this was due to a more sedentary lifestyle, or due to the whole body vibration and occasional heavy lifting involved in the role.
High job demand and low job control have been shown to predict low back pain (Sterud and Tynes, 2013).
A Japanese study found ‘interpersonal stress at workplace’ and ‘monotonous tasks’ to be predictive for low back pain (Matsudaira et al., 2012).
A Norwegian study found that the most consistent predictors of back pain were poor decision control, lack of empowering leadership and unfair leadership (Christensen and Knardahl, 2012).
As noted above, there are substantial limitations in all studies and evidence. Overall, there is no evidence that combat, work as a firefighter, policeman or healthcare worker is a risk factor for spondylosis or back pain, and fitness appears to be protective. Prolonged heavy manual work is a risk factor, particularly in roles such as dockworkers, farming and forestry, and in the military this may account for the increased risk in engineers particularly those with construction roles when there is a clear history of substantial periods of time spent working in construction.
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