Factors That Influence Exercise Tolerance

Due to the improvements in medical care, individuals with spinal cord injury (SCI) are now mirroring the nondisabled population in life expectancy and cause of death . In a study by Geisler and Jousse (1), renal (kidney) failure remained the leading cause of death, at 30.8 percent of the population with SCI studied . A 1983 study on the survival rates of individuals with SCI done by Geisler, showed a higher mortality rate than the population at large . However, an improvement was noted in life expectancy of the individual with SCI . The 1983 study concluded that mortality rate was highest for the complete SCI lesions and lowest for the partial lesions. The authors of the 1983 study (3) attributed the increase in longevity to the fact that even a small amount of continuity in spinal cord function allowed the body a more normal homeostasis (internal balance) . It was noted that the leading cause of death for paraplegics and incomplete tetraplegics was heart disease, while the leading cause of death for complete tetraplegia was respiratory disease . Another study done by Yekutiel in 1989 showed a higher incidence of hypertension and ischemic heart disease among those with SCI compared with age-matched controls : 34 percent versus 18 .6 percent (2) . Yekutiel found no correlation between level and extent of cord lesion or any other medical complications and cardiovascular disease . A recent study by Bauman reported that cardiovascular disease was the leading cause of death in individuals with SCI (3) . Cardiovascular disease appeared to occur at younger ages in the population with SCI than in the nondisabled population. The researchers concluded that this was due to the reduction in level of activity and adverse changes in body composition caused by the SCI . In addition, Bauman suggested that having a SCI had profound metabolic consequences that influenced the progression and severity of coronary artery metabolism . High density lipoprotein (HDL) cholesterol levels were markedly depressed and low density lipoprotein concentrations relatively elevated, in comparison to the nondisabled population . Other studies have found similar results for blood lipid profiles (3-5). These results are important as an inverse relationship exists between the HDL cholesterol level and coronary heart disease (6,7) . Krum explored further by looking into the risk factors for cardiovascular disease in the Australian population with SCI (7) . The risk factors investigated were serum cholesterol levels, blood pressure, cigarette smoking, glucose tolerance, physical activity, and family history. There was a low cardiac risk factor score in persons with SCI despite the reports of increased coronary heart disease incidence in these patients . Low cardiac risk scores were attributed to low diastolic blood pressure (DBP). A direct correlation was