Incidence is the proportion of a population initially free of the condition that develops it over a given period of time. In our review, incidence is standardized as the number of cases of traumatic SCI per million inhabitants a year. Tables 2 to 5 present the incidence of traumatic SCI by geographic area.
In North America, the incidence of traumatic SCI varied from 17 to 83 people per million inhabitants a year in the most recent studies; incident cases in the US military was considerably higher at 429 per million. The vast majority of the studies are based on Canadian (n=8) or American data (n=15).
In Europe, the estimated incidence varied from 3.3 to 130.6 individuals with traumatic SCI per million inhabitants a year. This reflects the experience of several countries including Bulgaria, Denmark, Finland, France, Germany, Iceland, Ireland, Italy, Norway, Portugal, Romania, Spain, The Netherlands, Estonia and Turkey.
In Asia, the incidence of traumatic SCI was reported between 6.7 and 246 persons per million inhabitants a year. There were 5 Taiwanese studies, 3 Japanese studies, 2 Chinese studies, 1 Russian and 1 Jordanian study.
In Oceania, the estimated incidence varied from 5.6 to 49.1 individuals with traumatic SCI per million inhabitants a year. There were 3 Australian studies, 12 from New Zealand and 1 from Fiji.
Our search did not capture any study focused on incidence or prevalence in an African country.
Time trends in SCI incidence
Of the 67 articles on incidence, 19 studies provided estimated incidence rates of traumatic SCI in at least 2 different periods of time. Most of those studies suggested an increasing incidence of traumatic SCI over the last decades, but three articles in Canada, Taiwan, and Australia reported a decreasing incidence. Interestingly, an updated analysis from Iceland found that while incidence appears to have dropped between the late 70’s and 90’s, it has returned to past levels in the late 00’s.
The most recent analysis from Canada found that in British Columbia, the incidence of SCI decreased from 42.2 to 32.5 per million between 1995 and 2004 (Lenehan et al. 2012). Pickett et al. (2006) found that the incidence of traumatic SCI in London (Ontario, Canada) increased from 21 to 49 people per million inhabitants a year between 1997 and 2000. Similarly, Starr-Bocian (1991) reported that the SCI incidence in Colorado (USA) increased from 26.5 to 38.8 individuals per million inhabitants a year between 1986 and 1990. Based on a broader time series from Olmsted County (Minnesota, USA), Griffin et al. (1985a) also found considerable increase in the SCI incidence from 22.2 people per million inhabitants a year between 1935 and 1944 to 70.8 people per million inhabitants a year between 1975 and 1981. In a Finnish study (Kannus et al. 2007), the incidence of traumatic SCI more than doubled from 52 individuals per million inhabitants in 1970 to 120 in 2004. Similarly, Maharaj (1996) documented a significant increase in the SCI incidence in Fiji from 5.6 to 17.9 people per million inhabitants a year between 1986 and 1991. In the most recent study, Hagen et al. (2009) documented an increase in the incidence of traumatic SCI from 6.2 to 26.3 individuals per million a year from the 1950s to the 1990s in Western Norway.
Differently, Chen et al. (1997) reported a reduction in the SCI incidence in Taiwan from 24.5 to 17.2 individuals per million a year between 1993 and 1996. Yeo (1993) also found a decreasing incidence of traumatic SCI in New South Wales (Australia) from 21.6 people per million inhabitants a year in 1987 to 15.6 individuals per million inhabitants a year in 1992. Similarly, Knutsdottir (1993) reported a decrease in the incidence of traumatic SCI in Iceland from 24 in the 1970s to 18 people per million a year in the 1980s.