Life expectancy after spinal cord injury

                                Dr. KS Dhillon

It is important to accurately predict life expectancy and identify factors

contributing to increased mortality following spinal cord injury (SCI). It is important for lifetime care planning, case management, and health promotion. Over the last 50 years, researchers have studied survival rates after SCI. They have reported factors such as gender, age at the time of injury, neurological level, degree of impairment, ventilator dependency, etiology, and the interval between injury and estimation of life expectancy as important predictors [1–15].

Data from the Model Systems in the United States is the largest and most influential source of information from which long-term trends in mortality rates and life expectancies have been estimated [16]. DeVivo [16] has shown continuing trends over the last 30 years towards improvement in acute survival rates. However, there was no similar reductions in longer-term mortality.

There have been relatively few studies that have examined

long-term survival and trends in standardized mortality ratios (SMRs)

over many decades. The current authors have previously reported on mortality rates and estimates of life expectancy in a cohort of 1453 individuals with SCI admitted to a spinal cord injury unit over a 40-year period [12]. There are several studies that have reported longer survival analyses in persons with SCI over a 50-year period in Great Britain [11] and Norway [15]. Frankel et al [11] have reported a 71–82% reduction in mortality over time. The most noticeable change is the proportion of surviving individuals with tetraplegia compared with paraplegia. Frankel et al [11] also showed a change in the ranking of the leading cause of death over time. In the early decades, death was related to the urinary tract and renal failure compared with respiratory system more recently.

Hagen et al [15] did not demonstrate a reduction in 1-year mortality after SCI over 5 decades. They noted survival of an increased proportion of older and more severely injured more recently.

DeVivo and colleagues [13,16,17,18] have shown that there have been

continuing trends over the last 20 years towards improved survival rates in the first year after SCI, unlike the general population. Similar progress for further reductions in long-term annual mortality rates is not apparent. After years of progressive improvements, recent data have suggested a pattern of slowing or possibly even reversal in the previous trend of diminishing mortality rates and

improving life expectancies. 

DeVivo, however, observed that this reversal appeared mostly due to increased mortality in the second post-injury year and to a lesser extent also in years 3–5 post-injury. Mortality rates for 10–20 years post-injury continued to fall slightly.

Recent studies from the Model Systems in USA also demonstrated improved acute survival following SCI, particularly in those more severely injured, presumably reflecting improved pre-hospital retrieval and trauma systems, intensive medical care and rehabilitation management.

The neurological level and degree of impairment, as well as age, are

important prognostic factors to be taken into account when estimating life expectancy. The most significant increases in mortality rates were seen in the group with C1–4 tetraplegia and American Spinal Injury Association Impairment Scale (AIS) grades A–C lesions, with SMRs ranging between 5.4 and 9.0 for the group of people 50 years or younger, and SMRs reducing with advancing current age.

Strauss et al [18] and Coll et al [19] have highlighted the importance of distinguishing not only between high and low levels of tetraplegia but also between complete (AIS grade A) and incomplete (AIS grades B and C) lesions when estimating life expectancy. The experience is worse for those with AIS grade A lesions in both the C1–4 and C5–8 groups when compared with incomplete lesions. The C1–4 group has significantly worse experience than the C5–8 group. Strauss et al [18] showed that C1–4 incomplete (AIS grades B and C) lesions may also carry a higher mortality risk. In applying these estimates of life expectancy, one should be careful not to discount expected improvements in the survival of patients who have sustained SCI.

DeVivo and Ivie [20] have demonstrated that being ventilator-dependent

carries a high risk of acute mortality, as well as a major reduction in

life expectancy. 

Model Systems in United States data demonstrates that around 4–5% of their SCI population still require mechanical ventilation on discharge [16]. It is likely that some of those persons with high-level tetraplegia, who are weaned successfully from the ventilator after several months in hospital due to borderline respiratory function, remain at higher risk of premature death due to late respiratory failure.

SMRs are not significantly elevated for causes of death associated with cancer (1.13) and ischaemic heart disease (1.77). This highlights the necessity for regular systems review, with close vigilance to respiratory and urinary health maintenance and psychosocial issues. 

Krause et al [21] by using logistic regression showed that, after adjusting for demographic characteristics and injury severity, measures of health status, community integration and economic status had small but statistically significant effects on likelihood of death during the next year. These authors and others have flagged the need for greater research attention be given to contextual factors, either personal or environmental, that may interact with age and impairment to further reduce life expectancy after SCI. In this regard, better understanding is required of the impact of pre-morbid education, health, and risktaking behaviours, as well as pre-existing conditions or co-morbidities, such as traumatic brain injury, depression and drug and alcohol use, lifestyle factors including smoking and exercise, as well as psychosocial variables, such as living circumstances, access to care and social support, finances and employment. This information can enable clearer interpretation of cross-sectional group mortality trends and adjustment to an individual taking into account risk-factor profiles, which may be valuable for medico-legal purposes, lifetime care planning, future service development and prevention initiatives. Regular monitoring of health and periodic functional review by a multidisciplinary team are recommended as important services for achieving maximum longevity and quality of life after SCI.

Conclusion

Although there have been improvements in survival and life expectancy over time, most notably in the group with paraplegia in comparison to 10 years ago, mortality rates after SCI remain elevated with life expectancy most significantly reduced in persons with higher level and more severe impairment. There is a need for future improvements that will require a greater understanding of and proactive attention to the way in which contextual factors, either environmental or personal, interact with age and impairment to contribute to the reduced life expectancy after SCI.

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