While prevalence is a measurement of all individuals affected by a condition at a particular time, incidence is a measurement of the number of new individuals who acquire a condition during a particular period of time. The incidence of SCI describes how many people have acquired an injury of the spinal cord within a predefined period of time. It is therefore a descriptive term for the risk of suffering from a certain condition or disease and represents an indirect indicator for the effectiveness of primary preventive measures.

The incidence of SCI including traumatic and non-traumatic lesions is estimated to be between 40 and 83/million/year, with an absolute estimated annual number of new cases worldwide around 250,000–500,000 [15]. The worldwide incidence of only traumatic SCI is estimated to be between 10.4 and 83/million/year [13].

However, these numbers must be interpreted with caution. The determination of the incidence of SCI is highly dependent on a variety of factors, which results in large variations.

Patients with traumatic SCI who die at the scene of the accident or pass away on their way to an emergency room are normally not included in any statistical data evaluation. This also applies to patients with a malignant disease in its final stage involving an SCI. These facts introduce a systematic bias to the overall incidence of SCI resulting in lower estimate.

Similar to the problem of determining a representative value for the prevalence of SCI, the database for determining the incidence of SCI is incomplete and inconsistent. Technical limitations and a systematic bias may be present in data collection in different countries. As a consequence, there are only rough estimates available.

Published data from different countries show enormous differences in the average incidence of SCI [7, 16, 17]. These differences might be explained by different age distributions, hazard potentials, and different levels of emergency treatment. According to a study, the annual incidence of new traumatic SCI rose significantly in persons 55 years and older. The proportion of tetraplegia and of incomplete injuries also increased. Additionally traumatic SCI occurs mostly at a young age, below 30 years [18, 19], whereas non-traumatic spinal cord disease affects people at a higher age, above 55 years.

In war zones or countries with a widespread availability of weapons or a high crime rate, the number of traumatic SCI is high, whereas gunshots or other forms of violence as causes for SCI play only a minor role in countries with restrictive laws on fire arms [20, 21]. The incidence of traumatic SCI in the mentioned countries and regions (Table 1.3) varies between 12 and 53/million [7, 10, 17, 24]. Even if data on the overall incidence are available for a large country, the regional incidence may vary to a large extent due to differences in industrialization and medical infrastructure, e.g., rural areas versus cities.

The incidence of non-traumatic SCI varies between 12 and 76/million population [7, 10, 26–28] (Table 1.4). In western industrial countries, the demographic change toward a dramatic increase in the elderly population has an enormous influence on the etiology of SCI, meaning that the percentage of non-traumatic SCI is constantly growing over the last decade [30].

With regard to gender, men are by far more affected by traumatic SCI [7, 24, 31] (Table 1.5). In case of non-traumatic SCI, the proportion of females is nearly equal to males [12, 29, 35] (Table 1.6). Respective gender proportions are robust and comparable in all countries worldwide.

The most common global causes for traumatic SCI are road traffic accidents followed by falls and violence. The proportion of road traffic accident-related SCI varies to a great degree for different regions of the world. The number of road traffic accidents is directly related to the population and traffic density but also depends on regionally quite differently developed road safety measures. In Africa, for instance, the proportion of traffic accident-related SCI (57 %) is almost twice as high as in Europe [31, 40], whereas the probability of a fall-related SCI in Europe is nearly twice as high as compared to Africa [31, 35]. A Chinese study shows that rapid progress in industrialization and the associated increase of traffic substantially influence the incidence and causes of traumatic SCI. Between 2000 and 2010, an increase of road traffic accident-related SCI to 51.2 % has been reported [41]. In other developing countries, traffic accidents are by far the most prominent cause of traumatic SCI (77 % in Lagos [42]). With 85 % the highest proportion of traffic accident-related SCI can be found in Saudi Arabia [43].

In children and juveniles, traffic accidents are the most common cause of paralysis worldwide. In the group of children with an age below 12 years, traffic accidents are the most frequent cause of traumatic SCI, higher than all other causes together [18, 19]. In the subpopulation with an age below 45 years, traffic accidents are the most common cause of SCI. However, after the age of 45, falls are the most likely cause for an SCI [20].

However, those numbers need to be seen from the perspective of regionally different populations. As an example, the high percentage of fall-related SCIs in older people in Europe can be easily explained by the demographic population structure in European countries [1]. This development is also found in the USA (“mean age at injury increased 9 years since the 1970s”) [43], in Canada (“significant increase in the mean age at injury from 30.23 to 45.768 years of age”) [44], and in Australia reporting a significantly increasing rate of fall-related injuries in elderly males [45].

People’s recreational and sport-related activities influence both the rate of SCI and the associated patterns of injury. The percentage of sport-related SCI in the overall traumatic SCI population is 1.7 % in Nigeria, 4.0 % in Germany, 10.0 % in the USA, and 14.1 % in the Netherlands [11, 28, 42, 46]. According to the available literature, there are six countries in which sports accounts for over 13 % of SCI (highest to lowest: Russia, Fiji, New Zealand, Iceland, France, and Canada). Diving, skiing, rugby, and horseback riding were identified as individual sports with the highest risk for SCI. For hockey, skiing, diving, and American football, almost all injuries are located at the cervical spinal cord level, while over half of horseback riding and snowboarding injuries are at the thoracic or lumbosacral level [47].

The number of traumatic SCI caused by firearms varies to a large extent in different countries. In Northern Europe the percentage is below 1 % of the overall traumatic SCI population, whereas in Brazil injuries of the spinal cord by the use of firearms are a common cause accounting for 16.9 % of all traumatic SCI cases [48].

As mentioned above the incidence represents, among other things, a good indicator in terms of effectiveness of primary measures for the prevention of SCI. For the validity of this statement, there are both positive and negative examples: in Germany the costs of treatment after accidents during work will be covered by a separate statutory accident insurance (workmen’s compensation). This is somehow a unique approach in the international context. The data from Germany show that the proportion of SCI caused by workplace accidents has decreased from 22 to 7 % of the total traumatic SCI population from 1985 to 2013 [11]. This can be attributed both to the lower risks for workplace-related injuries due to the general trend toward a modern industrial and information society with more indoor work places and also to the implementation of stricter occupational safety regulations. The latter is without doubt an example of successful primary prevention.

However, in another cause of traumatic SCI, diving into shallow water, primary preventive measures seem to be less effective. Data from Germany show that the percentage of cervical lesions resulting from shallow water diving persists on a constant level from 1985 to 2013 [11]. The proportion of SCI related to shallow water diving accounts for approximately 4 % of traumatic SCI. The introduction of several prevention campaigns did not yield a lower incidence. In contrast, prevention programs in the USA and Canada have been reported to successfully promote reduced rates of diving into shallow water accidents [49].

Few studies provide epidemiological data on non-traumatic SCI. Non-traumatic SCI has received more and more attention over the recent decades, whereas until the mid of the twentieth century, the percentage of traumatic SCI was reported to be more than 90 % with only few cases due to non-traumatic causes. The increase of non-traumatic SCI – a disease of the elderly – can, for the most part, be explained by the increase in life expectancy of the population in developed countries. This trend is normally linked to the occurrence of age-related diseases such as cardiovascular disorders, tumors, and infections of the spinal column or spinal cord itself. Developing countries tended to have a higher proportion of infections, particularly tuberculosis and HIV, although a number also reported tumors as a major cause [27].

A detailed analysis of over 1000 cases of non-traumatic SCI in 2012 in Germany attributed 26 % to tumors compressing the spinal cord, 20 % to infectious disease, and 16 % to ischemia. The most common non-traumatic cause (41 %) was degenerative spine diseases with associated spinal canal stenosis [11]. These proportions are comparable for all industrialized countries [26].

Non-traumatic SCI results much more often in incomplete paralysis compared to traumatic SCI [9, 11, 12, 26, 28, 29, 41, 42] (Tables 1.7 and 1.8).