Aging is a highly complex phenomenon that can be examined at the genetic, cellular, organ-system, and psychosocial levels (Aldwin & Gilmer 2004). Although there are some conflicting evidence on which systems decline, for the most part, persons aging with SCI exhibit decreases in health status and physical functioning over time (see Table 2), which could serve as markers of premature aging.
In this section, 1 systematic review (see Table 2) on physiological aging after SCI is reviewed.
In this systematic review (Hitzig et al. 2011), the hypothesis that SCI represents a model for premature aging is supported by level 5 evidence for the cardiovascular and endocrine systems, level 2, 4 and 5 evidence for the musculoskeletal system, and limited level 5 evidence for the immune system. Only a few level 4 and 5 studies for the respiratory system were found. Evidence on the genitourinary system, gastrointestinal system, and for skin and subcutaneous tissues provide level 4 and 5 evidence that premature aging may not be occurring in these systems.
SCI may represent a partial model for premature aging.
There is stronger evidence that the endocrine and musculoskeletal systems are prematurely aging.
There is limited evidence that the respiratory, skin and subcutaneous tissues, genitourinary, and gastrointestinal systems are prematurely aging.
There is weak and limited evidence that the immune and nervous system are prematurely aging.
The following sections review each body system individually, including the cardiovascular and endocrine systems (see Table 3), immune system (see Table 4), musculoskeletal system (see Table 5), respiratory system (see Table 6), nervous system (see Table 7), skin and subcutaneous tissues (see Table 8), and the genitourinary and gastrointestinal systems (see Table 9).