High-intensity interval training in individuals with spinal cord injury

Incidence and prevalence

The National Spinal Cord Injury Statistical Center (NSCISC) estimates 291,000 people are living with an SCI in the United States with 17,730 new cases each year, or 54 per million ( ). Other studies have found similar incidence rates, ranging from 52 to 56.4 per million ( ); however, due to varying methodologies, other reports include prevalence estimates of 1.5 million to 2.6 million ( ). For decades, the typical person acquiring SCI was 29; however, that has increased to 43, likely due to an increase in the etiology of falls among an aging population. People with newly acquired SCI are typically male (78%) and white (59.5%) with leading causes of injury vehicle crashes (39.3%) and falls (31.8%). The majority of injuries are incomplete, either tetraplegia (47.6%) or paraplegia (19.9%) followed by complete paraplegia (19.6%) and complete tetraplegia (12.3%).

Healthcare and economic burden

Healthcare burden is largely dependent upon the degree of severity of the SCI with hospitalizations in the first year of injury, which includes the bulk of the direct cost estimated at 1.7 billion in the United States ( ). For example, an individual with tetraplegia and vent-dependent has an average healthcare expenditure over 1.2 million dollars in the first year after injury with almost $200,000 in subsequent years, whereas someone with paraplegia cost estimates include $550,381 for the first year and $72,909 in subsequent years ( ). The first year after following injury is the costliest and the most critical to the life of the person with SCI, as life expectancy increases significantly after living past the first year of injury. For individuals injured at 20 years old, estimated life loss is 7 years among individuals with paraplegia and 48 years of life loss among individuals with higher injury levels and vent dependency. In addition to direct cost and life loss, indirect cost, such as loss of earnings and productivity, is estimated at $76,237 per year.

Depending on the level of injury and personal response, many individuals do not return to full-time work or even part-time work. Data from NSCISC show 66% of individuals working at time of injury with only 17% working 1 year out and 23% working 10 years after injury. Lastly, length of stay for rehabilitation after sustaining an SCI has been reduced from 98 to 34 days over the last 50 years ( ). Post-acute rehabilitation offers people with SCI the benefit of individualized, intensive training before returning home. However, shorter length of stay and lack of intensive programming for the home has been linked to higher incidence of rehospitalization due to secondary health conditions, as well as increased discharge to institutional settings rather than the home, all of which drive healthcare cost ( ; ; ).