Although the immune system is affected by a number of factors, including nutritional status, stress, exercise, neuroendocrine change, and disease, there is consensus that immune functioning undergoes some age-related declines (Miller 1996; Burns & Leventhal 2000; Rabin 2000). There is limited evidence on the effects of SCI on the immune system with aging, but several studies (i.e., Lyons 1987; Nash 1994; Kliesch et al. 1996; Campagnolo et al. 1999; Cruse et al. 2000) suggest deficits in immune functioning. Hence, there is greater likelihood of immune impairment in the aging SCI population compared to the non-disabled population (Charlifue & Lammertse 2002).
In this section, 1 longitudinal study and 4 cross-sectional studies (see Table 4) on the immune system after SCI are reviewed.
One study provides level 4 evidence (Frisbie 2010) that persons with SCI have a high prevalence of anemia and hypoalbuminemia which might serve as markers for infection. Additionally, two studies provide level 5 evidence that this system is compromised at the acute and chronic stages of SCI compared with AB controls. Persons with acute and chronic SCI who have complete injuries (N = 5) demonstrated altered immune function compared to AB controls (Campagnolo et al. 1994). As well, Campagnolo et al. (1999) compared persons with SCI (N = 18) to AB controls (N = 18), and found that persons with SCI have higher levels of cortisol and dehydroepiandrosterone sulfate (DS), but comparable levels of dehydroepiandrosterone, adrenocorticotropin, and prolactin. Additionally, they found that DS and dehydroepiandrosterone were higher in persons with tetraplegia compared to controls, but no differences were found between persons with paraplegia and controls. Campagnolo et al. (1999) concluded that immune functioning is altered after SCI, but may be mediated by level of injury. Thus, persons with tetraplegia may have a greater degree of alteration to the immune system compared to persons with paraplegia. Unfortunately, the sample sizes in both studies were quite small.
Further research related to the immune system is required given that older age of SCI-onset leads to poorer outcomes (Prusmack et al. 2006), and SCI of long duration results in increased infection (Whiteneck et al. 1992). Because persons with SCI are treated with antiobiotics throughout their lives, there are a number of important questions regarding the long-term effects on the immune system (Adkins 2004).
There is Level 4 evidence that persons with SCI have a prevalence of anemia and hypoalbuminemia (Frisbie 2010), which might serve as markers for infection.
There is Level 5 evidence (Campagnolo et al. 1994; Campagnolo et al. 1999; Furlan et al. 2006) that the immune function of persons with acute and chronic SCI is compromised compared to the able-bodied population, but there is no influence due to aging.
Immune function after SCI at both the acute and chronic phase is compromised compared to able-bodied controls, but age may not play an important role.