The results of our systematic review suggest a relatively broad variation of incidence and prevalence of traumatic SCI among distinctive geographic regions. While most of the prior studies indicated an increasing incidence of traumatic SCI over the last decades, a few reports suggested trends towards reduction of its incidence over the past years. Furthermore, prior studies consistently suggested an increasing prevalence of traumatic SCI over the past few decades (Griffin et al. 1985b; Starr-Bocian 1991; Maharaj 1996; Pickett et al. 2003). Those differences can be partially attributed to methodological divergences or limitations, such as the use of national databases versus hospital databases or regional chart reviews or surveys. Discrepancies among the results can also be associated with country-related differences regarding social-economic or cultural factors, public health and prevention policies, and healthcare systems all of which can influence occurrence and survival and thus the prevalence of traumatic SCI.
In our review, Europe and Asia (i.e. continents with more heterogeneous populations) showed a greater range of incidence in comparison with Oceania and the Americas, which are essentially represented by Australia, Canada and the United States. One may speculate that diversity of societies, economies, healthcare systems and public health policies in Europe and Asia amplifies differences regarding health status including traumatic SCI. In addition to this contextualization, there are potential methodological issues and limitations with regard to data collection and quality. The paucity of validation studies of registries and databases is alarming and suggests caution when comparing derived results. For instance, under-ascertainment and misclassification of cases is a major methodological issues in studies focused on incidence and prevalence of any health condition.
Our review also indicates that the incidence of traumatic SCI increased in Canada, the United States, Finland, Fiji and Norway, whereas they reduced in Taiwan, Iceland and New South Wales. Again, methodological considerations should be taken prior to interpreting those discrepancies. Further studies are required to confirm those trends and, more importantly, to determine the reasons for such differences which may be applied to improve the survival and health status of people with SCI in other countries.
The prevalence studies in our review suggest that the number of people with traumatic SCI can greatly vary depending upon the geographic region. Again, underestimation of the numerator may play a key role in the lower prevalence reported in some of those previous studies. Improvement of economics, quality of life and healthcare apparatus actually contributed to an increased life span of person with traumatic SCI as documented in previous studies (DeVivo et al. 1999; Strauss et al. 2006). Therefore, a boost in the prevalence can at least partially be explained by an increase in the individuals’ life span after a traumatic SCI. However, prevalence could also be amplified by a real increase in the incidence of traumatic SCI as heralded in a number of those studies.
The results of this review indicate differences among geographic regions regarding the incidence and prevalence of traumatic SCI. Also, an increase in the incidence and prevalence of traumatic SCI has been reported in several countries worldwide. However, this comprehensive review of the literature also emphasizes the need for further studies on incidence and prevalence of traumatic SCI. A better understanding of the reasons for the discrepancies in the incidence and prevalence among those geographic regions may inform effective strategies to reduce the global burden of this disabling health condition.