Sex-based differences in incidence and presentation have been described for some, but not all, conditions of the spine. For example, adolescent idiopathic scoliosis, one of the most common diseases of the spine in adolescence, is somewhat more common in females, and females are much more likely to present with larger curves. The incidence of scoliosis among adults, which includes a wider range of diagnoses than adolescent idiopathic scoliosis, does not appear to differ by sex, and there appears to be no sex-based differences in magnitude of curves.1 Ankylosing spondylitis is diagnosed more frequently in men. However, women who present with this condition tend to be older than their male counterparts, have a shorter duration of disease, be more likely to have thoracic spine involvement, and be less likely to be HLA-B27 positive.2
Among the common conditions of the spine, data are often conflicting regarding any sex-based differences in incidence, most likely reflecting their multifactorial etiology. Degenerative disc disease and lumbar radiculopathy, for example, have been reported to be more common in men, more common in women, or equal in lifetime sex-based risk. Women with degenerative disc disease have been noted to present with this condition when they are approximately 10 years older than men,3 perhaps reflecting differences in activity and mechanical loading. Among a young active military population, degenerative disc disease4 and lumbar radiculopathy5 were found to be more common among women, although female sex was less of a risk factor than older age for both conditions.
A variety of risk factors have been described to account for any noted sex-based differences among spine conditions. The most obvious difference would be the influence of sex hormones. Studies related to hormones and spinal deformity, which is more common in women, have shown no clear relationship, while in cases of ankylosing spondylitis, which is more common in men, studies have shown no differences in adrenal or gonadal sex hormones6 to explain this predominance.
As with other conditions, any sex-based differences are likely multifactorial. Schoenfeld5 postulated that these differences might reflect hormonal influences as well as differing responses of the spine to loading and physical activity. Among a cohort of asymptomatic young adults,7 it was found that the spine from T1-L5/S1 as a whole, and the individual high thoracic and lumbar vertebrae, were more dorsally inclined in women than in men. The authors hypothesized that this could make the spine less rotationally stable in women, in certain circumstances resulting in the initiation and/or progression of spinal conditions, such as scoliosis.
The potential impact of sex on other spine conditions has also been studied, without conclusive results. Increased paraspinous muscle degeneration has been suggested to correlate with incidence of low back pain,8,9 and in studying a cohort of symptomatic adult patients, it was found that women were more likely than men to demonstrate fatty infiltration of their paraspinous muscles on MRI. Sex-based differences have also been identified in paraspinous muscle fiber and type.10 However, the impact of sex on the development of low back pain. and any cause-and-effect relationship between low back pain or other spine conditions and changes in paraspinous muscle composition, has not been elucidated.
Women accounted for 55% of the 68.5 million total health care visits for back or neck pain in 2010, slightly more than the 51% of the population they represent. Total health care visits include hospital discharges, ED and outpatient clinic visits, and physician office visits. (Reference Table 9A.2 PDF [1] CSV [2])
Women also accounted for 54% of 488,000 hospital discharges for back pain that involved a spinal fusion procedure. (Reference Table 9A.2 PDF [1] CSV [2])
Women reported taking bed days for back and neck pain in higher numbers than men do. They also reported an average bed stay of about one-half day longer, 7.8 days in the previous 12 months, compared to a mean of 7.4 days for men. Overall, women accounted for 58% of total bed days in a previous 12-month period. (Reference Table 9A.2 PDF [1] CSV [2])
Men, however, report losing more workdays in a 12-month period than women do, accounting for 59% of lost workdays reported in 2012. Although slightly fewer numbers of men reported lost workdays than did women, they lost an average of one day of work more than women did, 11.9 days versus11.0 days lost. (Reference Table 9A.2 PDF [1] CSV [2])
Links:
[1] https://www.boneandjointburden.org/docs/T9A.2.pdf
[2] https://www.boneandjointburden.org/docs/T9A.2.csv