Cardiovascular Health
Introduction
Persons with spinal cord injury (SCI) currently have an increased life expectancy owing to improvements in medical treatment (Rick Hansen Spinal Cord Injury Registry 2004). The majority of SCIs (80%) occur in individuals who are under 30 years of age (Rick Hansen Spinal Cord Injury Registry 2004, ICORD 2003,). Therefore, persons with SCI are susceptible to the same chronic conditions across the lifespan as able-bodied persons. In fact, cardiovascular disease (CVD) is the leading cause of mortality in both able-bodied individuals and persons with SCI (Whiteneck et al 1992). However, there appears to be an earlier onset of CVD and/or an increased prevalence of CVD in persons with SCI (Bauman et al 1999b, DeVivo et al 1993, Whiteneck et al 1992, Yekutiel et al 1989). The separation of the autonomic nervous system from the superior brain centres after injury results in a series of changes that markedly affect the cardiovascular health of persons with SCI (Bravo et al 2004). Adrenergic dysfunction, poor diet, and physical inactivity are thought to play key roles in the elevated risk for CVD in SCI (Warburton et al 2007b).
As reviewed by Myers et al. (2007) there is consistent information indicating that there is a higher prevalence of CVD in persons with SCI in comparison to ambulatory populations (Groah et al 2001). For instance, the prevalence rates of symptomatic CVD in SCI have approximated 30%–50% in comparison to 5%–10% in the general able-bodied population (Myers et al 2007). Moreover, Bauman and colleagues revealed that the prevalence of asymptomatic CVD was 60%–70% in persons with SCI ( Bauman et al 1994, Bauman et al 1993). It also appears that persons with SCI have increased CVD-related mortality rates and those with tetraplegia experience mortality at earlier ages in comparison to able-bodied individuals (Myers et al 2007, DeVivo et al 1999, Whiteneck et al 1992). These are alarming statistics, which place a significant burden upon the patient, his/her family, and society as a whole.
Physical inactivity is a major independent risk factor for CVD and premature mortality (Warburton et al 2006b). Unfortunately, physical inactivity and marked deconditioning are highly prevalent among persons with SCI (Jacobs and Nash 2004). Also, it appears that the ordinary activities of daily living are not adequate to maintain cardiovascular fitness in persons with SCI (Hoffman 1986). It is likely that low levels of physical activity and fitness (as a result of wheelchair dependency) explain (in part) the increased risk for CVD (Myers et al 2007). Marked inactivity associated with SCI has been associated with lower high-density lipoprotein (HDL) cholesterol ( Manns et al 2005, Schmid et al 2000); elevated low-density lipoprotein (LDL) cholesterol (Schmid et al 2000); triglycerides ( Manns et al 2005, Schmid et al 2000); total cholesterol levels (Schmid et al 2000); abnormal glucose homeostasis (Manns et al 2005, Elder et al 2004); increased adiposity ( Manns et al 2005, Elder et al 2004); and excessive reductions in aerobic fitness ( Manns et al 2005, Schmid et al 2000). It is important to note that SCI presents an additional risk for CVD above that seen in able-bodied individuals owing to the marked decrease in physical activity and injury-related changes in metabolic function (Bravo et al 2004). Moreover, a reduction in cardiovascular fitness may also lead to a vicious cycle of further decline, which results in a reduction in functional capacity and the ability to live an independent lifestyle. Based on the available literature, it is clear that effective exercise interventions are required to slow the progression of multiple risk factors for CVD and other chronic diseases (e.g. obesity, type 2 diabetes) in persons with SCI.
The current chapter summarizes and updates the literature regarding the risk for CVD in persons with SCI. This chapter also evaluates critically the level of evidence regarding the effectiveness of varied forms of exercise rehabilitation in increasing cardiovascular fitness and attenuating the risk for CVD in persons with SCI. Table 1 contains a definition of the commonly used terms and/or abbreviations in this chapter.
