**Author details**

Christian Chukwukere Ogoke

Address all correspondence to: chrischikere@yahoo.com

Mother Healthcare Diagnostics and Hospital, Owerri, Imo State, Nigeria

### **References**


[8] Hagberg B. Nosology and classification of cerebral palsy. Giorn Neuropsich Eta Evolution. Suppl 1989;**4**:12-17

**Acknowledgements**

40 Cerebral Palsy - Clinical and Therapeutic Aspects

**Conflict of interest**

**Author details**

**References**

Christian Chukwukere Ogoke

10.1017/s001216220500112x

spen.2004.01.002

Journal. 2003;**326**(7396):970-974

DOI: 1016/j.pmr.2009.06.001

Address all correspondence to: chrischikere@yahoo.com

Participation. Geneva: WHO; 2001. ICIDH-2

Mother Healthcare Diagnostics and Hospital, Owerri, Imo State, Nigeria

[1] Bax M, Goldstein M, Rosenbaum P, Paneth N. Proposed definition and classification of cerebral palsy. Developmental Medicine and Child Neurology. 2005;**47**:571-576. DOI:

[2] Rosenbaum P. The definition and classification of cerebral palsy: Are we any further

[3] World Health Organization. International Classification of Impairment, Activity and

[4] Rosenbaum P, Stewart D. The WHO international classification of functioning, disability and health: A model to guide clinical thinking, practice and research in the field of cerebral palsy. Seminars in Pediatric Neurology. 2004;**2**(1):5-10. DOI: 10.1016/j.

[5] Rosenbaum P. Cerebral palsy: What parents and doctors want to know. British Medical

[6] Pakula AT, Braun KVN, Yeargin-Allsopp M. Cerebral palsy: Classification and epidemiology. Physical Medicine and Rehabilitation Clinics of North America. 2009;**20**:425-425.

ahead in 2006? Neuropsychopharmacology Reviews. 2006;**7**(11):e569

[7] Minear WL. A classification of cerebral palsy. Pediatrics. 1956;**18**:841-852

chapter.

None.

I am grateful to Professor Sylvester O. Iloeje for his assistance and extend my thanks to all staff of Mother Healthcare Diagnostics & Hospital, 5B Okigwe Road, Owerri and department of Paediatrics, Federal Medical Centre, Owerri. Thanks too to my beautiful wife Mrs. Linda Chigozie Ogoke for all her support during the period of writing up of this book


[21] Ganong WF. Control of posture and movement. In: Review of Medical Physiology. 22nd ed. Singapore: McGraw-Hill; 2005. pp. 202-222

**Section 3**

**Clinical Aspects of Cerebral Palsy**


**Clinical Aspects of Cerebral Palsy**

[21] Ganong WF. Control of posture and movement. In: Review of Medical Physiology. 22nd

[22] Nottidge VA, Okogbo ME. Cerebral palsy in Ibadan, Nigeria. Developmental Medicine

[23] Ogunlesi T, Ogundeyi M, Ogunfowora O, Olowu A. Socio-clinical issues in cerebral palsy in Sagamu, Nigeria. South African Journal of Child Health. 2008;**2**(3):120-122 [24] Gorter JW, Rosenbaum PL, Hanna SE, Palisano RJ, Bartlett DJ, Russell DJ, et al. Limb distribution, type of motor disorders and functional classification of cerebral palsy: How do they relate? Developmental Medicine and Child Neurology. 2004;**46**:461-467. DOI:

[25] Nelson KB, Ellenberg JH. Antecedents of cerebral palsy 1: Univariate analysis of risks.

[26] Nelson KB, Ellenberg JH. Antecedents of cerebral palsy: Multivariate analysis of risks.

[27] Korzeniewski SJ, Birbeck G, Delano MC, Potchen MJ, Paneth N. A systematic review of neuroimaging for cerebral palsy. Journal of Child Neurology. 2008;**23**(2):216-227. DOI:

[28] Hou M, Zhao JH, Yu R. Recent advances in dyskinetic cerebral palsy. World Journal of

[29] Iloeje SO, Ogoke CC. Factors associated with the severity of motor impairment in children with cerebral palsy seen in Enugu, Nigeria. South African Journal of Child Health.

[30] Paulson A, Vargus-Adams J. Overview of four functional classification systems com-

[31] Eliasson AC, Ullenhag A, Wahlstrom U, Krumlinde-Sundholm L. Mini-macs: Development of the manual ability classification system for children younger than 4 years of age with signs of cerebral palsy. Developmental Medicine and Child Neurology. 2016;**59**:

[32] Palisano RJ, Rosenbaum P, Bartlett D, Livingston MH. GMFCS—Expanded & Revised © 2007. Can Child Centre for Childhood Disability Research, McMaster University

[33] Plasschaert VF, Ketelaar M, Nijnuis MG, Enkelaar L, Gorter JW. Classification of manual abilities in children with cerebral palsy under 5 years of age: How reliable is the manual

ability classification system? Clinical Rehabilitation. 2009;**23**:164-170

American Journal of Diseases of Children. 1985;**139**:1031-1038

The New England Journal of Medicine. 1986;**315**:81-86

2017;**11**(3):112-116. DOI: 10.7196/SAJCH.2017.v11i3.1246

monly used in cerebral palsy. Children. 2017;**4**(30):1-10

ed. Singapore: McGraw-Hill; 2005. pp. 202-222

and Child Neurology. 1991;**33**:241-245

10.1017/s0012162204000763

42 Cerebral Palsy - Clinical and Therapeutic Aspects

10.1177/0883073807307983

72-78. DOI: 10.1111/dmcn.13162

Pediatrics. 2006;**1**:23-28

**Chapter 3**

Provisional chapter

**Survival, Mortality, and Life Expectancy**

Cerebral palsy (CP) is a heterogenous condition, with level of disability ranging from immaterial to profound. In concert with the continuum of level of severity of disability/ independent functioning, health care needs, therapies, medications, surgical interventions, costs of care, daily demands on parents and other family members, and expectations for the future in terms of education, employment, and other milestones of life all vary widely. Similarly, life expectancy in CP follows a continuum, from far lower than to potentially as high as general population life expectancy, that parallels the continuum of levels of disability. Here we review the literature documenting this, and examine the specific factors that are known to be strongly associated with mortality and longevity in CP. We also examine the evidence regarding causes of death in CP, and present some new findings related to this. Finally, we outline important methodological considerations for

DOI: 10.5772/intechopen.80293

Keywords: cerebral palsy, life expectancy, survival, mortality, developmental disability

Just as Americans headed home for the year-end holidays, the Centres for Disease Control and Prevention (CDC) issued its annual report on mortality—which had no news to celebrate. According to the report, published on December 21st, life expectancy in America fell in 2016, for the second year in a row. An American baby born in 2016 can expect to live on average 78.6 years, down from 78.9 in 2014. The last time life expectancy was lower than in the preceding year was in 1993. The last time it fell for two consecutive years was in 1962-1963. -

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Survival, Mortality, and Life Expectancy

Steven M. Day and Robert J. Reynolds

Steven M. Day and Robert J. Reynolds

http://dx.doi.org/10.5772/intechopen.80293

future research in this area.

The Economist, 4 January 2018 [1].

Abstract

1. Introduction

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

#### **Survival, Mortality, and Life Expectancy** Survival, Mortality, and Life Expectancy

Steven M. Day and Robert J. Reynolds Steven M. Day and Robert J. Reynolds

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.80293

#### Abstract

Cerebral palsy (CP) is a heterogenous condition, with level of disability ranging from immaterial to profound. In concert with the continuum of level of severity of disability/ independent functioning, health care needs, therapies, medications, surgical interventions, costs of care, daily demands on parents and other family members, and expectations for the future in terms of education, employment, and other milestones of life all vary widely. Similarly, life expectancy in CP follows a continuum, from far lower than to potentially as high as general population life expectancy, that parallels the continuum of levels of disability. Here we review the literature documenting this, and examine the specific factors that are known to be strongly associated with mortality and longevity in CP. We also examine the evidence regarding causes of death in CP, and present some new findings related to this. Finally, we outline important methodological considerations for future research in this area.

DOI: 10.5772/intechopen.80293

Keywords: cerebral palsy, life expectancy, survival, mortality, developmental disability

#### 1. Introduction

Just as Americans headed home for the year-end holidays, the Centres for Disease Control and Prevention (CDC) issued its annual report on mortality—which had no news to celebrate. According to the report, published on December 21st, life expectancy in America fell in 2016, for the second year in a row. An American baby born in 2016 can expect to live on average 78.6 years, down from 78.9 in 2014. The last time life expectancy was lower than in the preceding year was in 1993. The last time it fell for two consecutive years was in 1962-1963. - The Economist, 4 January 2018 [1].

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The concept of life expectancy is familiar to most people by virtue of reports in newspapers, online sources, or on television or radio. Comparisons of life expectancy at birth in various industrialized countries are common, and thus many people may know or will not be surprised to find that life expectancy is higher in Japan than it is in the US, or that in Russia it is lower than in most countries of Europe. Many may also have some general ideas as to why such differences may exist: diet, exercise, smoking prevalence, access to healthcare may all contribute. Mortality is the ultimate endpoint for studies of health and wellbeing, and life expectancy is one way to summarize the survival and mortality experiences of different groups of people.

CP, life expectancy can be a critical factor in developing and valuing a life-care plan, the expected present value of which may be a large part of potential damages in such litigation.<sup>1</sup> Our interest in this chapter is to provide information based on sound scientific principles and

Survival, Mortality, and Life Expectancy http://dx.doi.org/10.5772/intechopen.80293 47

Life expectancy (LE) is the arithmetic average survival time remaining for a cohort, hypothetical or real. In more technical statistical terms, it is the expected value of a population of random survival times. Alternatively, one can think of it as the average survival time for an individual member of a given population or cohort if such an individual could (hypothetically)

In order to understand the meaning of life expectancy, and to gain insight into the questions posed above, a basic understanding of the life table is extremely helpful. As we shall see, information presented in a life table can also be set out in, or gleaned from, a survival curve. An understanding of the relationship between the life table and its corresponding survival curve will be helpful in understanding life expectancy per se, and in understanding the connection between many studies of long-term survival of children and adults with cerebral palsy, many of which report survival curves or the equivalent, and life tables and life expectancy.

Table 1 is an abbreviated version of the latest life table (2017 table based on 2013 data) for all US persons (males and females combined) from the US National Center for Health Statistics (NCHS) [2]. Life expectancy at each whole integer age is given in the column labeled e(x). We can see from Table 1, for example, that the LE in the US is 78.8 years at birth; 50.1 remaining years at age 30 years; 23.2 remaining years at age 60; and 2.3 remaining years at age 100. Generally, the meaning of LE is the average remaining lifespan from a given age. This is not to be confused with the age to which a cohort of a given age is expected to live. Thus LE is 78.8 remaining years, to age 78.8, for newborns of age 0; it is 2.3 remaining years, to age 102.3, for

In addition to LE, a life table provides other information, including (for example) (1) the likelihood that a person born today will be alive at age 50, 80, or 100; (2) the 5-year survival probability from any age; (3) the probability of surviving beyond age 70; (4) the median survival time, that is, the time at which half of the hypothetical cohort will have died and beyond which half will continue to live; and (5) the conditional probability of living to age 65 given one has already lived to age 40. Depending on the context, any of these figures may be of greater interest or importance than the LE at a given age; however, LE is the most often cited

For full disclosure, we acknowledge that we, the authors of this chapter, have provided expert opinions on behalf of both

plaintiffs and defendants in such legal cases, and will undoubtedly do so in the future.

evidence.

2. The life table and survival curve

those fortunate enough to survived to age 100.

live life over and over again.

2.1. The life table

1

Few give much thought as to how exactly we can know that life expectancy in America fell in 2016, as The Economist reports [1]. To fully understand how we can know that (or know that life expectancy in Japan is higher than it is in the US, or that life expectancy for the Hispanic population in the US is greater than it is for people in the US overall, or that women have a greater life expectancy than men almost universally), one needs to understand what life expectancy is, and how it is calculated. In this chapter we will begin with a brief review of the life table, the principle tool used by demographers, actuaries, biostatisticians and epidemiologists in examining questions of life expectancy. In these contexts, life expectancy has a very specific meaning, and must not be confused with the actual survival time of a given individual.

Just as it is known that life expectancy in Japan is greater than in the US, it is also known that life expectancy for groups of people with differing medical conditions, behavior patterns, or professions can differ. It is probably not surprising, for example, that children born with complex congenital heart defects have a lower life expectancy than that of any general population (GP) of age- and sex-matched children (including all comers, with or without heart defects). Similarly, persons with various types of cancer have life expectancies that are lower than those of age- and gender-matched populations (including all comers with or without cancer). Within the population of children born with congenital heart defects, or persons with cancer, variation in life expectancy exist as the group is sub-divided according to level of complexity of heart defects, or site/stage/grade/histology of tumor. Similar statements apply when considering the life expectancy in cerebral palsy (CP). That people with cerebral palsy compose a heterogeneous group will be well understood by most readers of this chapter; as we shall see, the life expectancy of the group as a whole and of meaningfully defined subgroups differ dramatically as a consequence.

The life expectancy of persons with cerebral palsy (CP) is of interest to many audiences for varying reasons. Parents would like to know how long they might have to fulfill the oftenchallenging physical, emotional, and monetary demands of caring for a child with special needs; they wonder how long they might get to enjoy the rewards of that relationship and wonder and worry whether their child might outlive them. Resource allocation for long-term care facilities depends in part on their residents' longevity, a fact of interest to governments or private insurance companies providing funding for such facilities. Life insurance and structured settlement underwriters must consider life expectancy and other information in a life table in pricing insurance or annuities. Finally, and perhaps most controversially, in cases of litigation related to medical care and treatment alleged to have contributed to an outcome of CP, life expectancy can be a critical factor in developing and valuing a life-care plan, the expected present value of which may be a large part of potential damages in such litigation.<sup>1</sup> Our interest in this chapter is to provide information based on sound scientific principles and evidence.

#### 2. The life table and survival curve

Life expectancy (LE) is the arithmetic average survival time remaining for a cohort, hypothetical or real. In more technical statistical terms, it is the expected value of a population of random survival times. Alternatively, one can think of it as the average survival time for an individual member of a given population or cohort if such an individual could (hypothetically) live life over and over again.

In order to understand the meaning of life expectancy, and to gain insight into the questions posed above, a basic understanding of the life table is extremely helpful. As we shall see, information presented in a life table can also be set out in, or gleaned from, a survival curve. An understanding of the relationship between the life table and its corresponding survival curve will be helpful in understanding life expectancy per se, and in understanding the connection between many studies of long-term survival of children and adults with cerebral palsy, many of which report survival curves or the equivalent, and life tables and life expectancy.

#### 2.1. The life table

The concept of life expectancy is familiar to most people by virtue of reports in newspapers, online sources, or on television or radio. Comparisons of life expectancy at birth in various industrialized countries are common, and thus many people may know or will not be surprised to find that life expectancy is higher in Japan than it is in the US, or that in Russia it is lower than in most countries of Europe. Many may also have some general ideas as to why such differences may exist: diet, exercise, smoking prevalence, access to healthcare may all contribute. Mortality is the ultimate endpoint for studies of health and wellbeing, and life expectancy is one way to summarize the survival and mortality experiences of different groups

Few give much thought as to how exactly we can know that life expectancy in America fell in 2016, as The Economist reports [1]. To fully understand how we can know that (or know that life expectancy in Japan is higher than it is in the US, or that life expectancy for the Hispanic population in the US is greater than it is for people in the US overall, or that women have a greater life expectancy than men almost universally), one needs to understand what life expectancy is, and how it is calculated. In this chapter we will begin with a brief review of the life table, the principle tool used by demographers, actuaries, biostatisticians and epidemiologists in examining questions of life expectancy. In these contexts, life expectancy has a very specific meaning, and must not be confused with the actual survival time of a given individual. Just as it is known that life expectancy in Japan is greater than in the US, it is also known that life expectancy for groups of people with differing medical conditions, behavior patterns, or professions can differ. It is probably not surprising, for example, that children born with complex congenital heart defects have a lower life expectancy than that of any general population (GP) of age- and sex-matched children (including all comers, with or without heart defects). Similarly, persons with various types of cancer have life expectancies that are lower than those of age- and gender-matched populations (including all comers with or without cancer). Within the population of children born with congenital heart defects, or persons with cancer, variation in life expectancy exist as the group is sub-divided according to level of complexity of heart defects, or site/stage/grade/histology of tumor. Similar statements apply when considering the life expectancy in cerebral palsy (CP). That people with cerebral palsy compose a heterogeneous group will be well understood by most readers of this chapter; as we shall see, the life expectancy of the group as a whole and of meaningfully defined subgroups

The life expectancy of persons with cerebral palsy (CP) is of interest to many audiences for varying reasons. Parents would like to know how long they might have to fulfill the oftenchallenging physical, emotional, and monetary demands of caring for a child with special needs; they wonder how long they might get to enjoy the rewards of that relationship and wonder and worry whether their child might outlive them. Resource allocation for long-term care facilities depends in part on their residents' longevity, a fact of interest to governments or private insurance companies providing funding for such facilities. Life insurance and structured settlement underwriters must consider life expectancy and other information in a life table in pricing insurance or annuities. Finally, and perhaps most controversially, in cases of litigation related to medical care and treatment alleged to have contributed to an outcome of

of people.

46 Cerebral Palsy - Clinical and Therapeutic Aspects

differ dramatically as a consequence.

Table 1 is an abbreviated version of the latest life table (2017 table based on 2013 data) for all US persons (males and females combined) from the US National Center for Health Statistics (NCHS) [2]. Life expectancy at each whole integer age is given in the column labeled e(x). We can see from Table 1, for example, that the LE in the US is 78.8 years at birth; 50.1 remaining years at age 30 years; 23.2 remaining years at age 60; and 2.3 remaining years at age 100. Generally, the meaning of LE is the average remaining lifespan from a given age. This is not to be confused with the age to which a cohort of a given age is expected to live. Thus LE is 78.8 remaining years, to age 78.8, for newborns of age 0; it is 2.3 remaining years, to age 102.3, for those fortunate enough to survived to age 100.

In addition to LE, a life table provides other information, including (for example) (1) the likelihood that a person born today will be alive at age 50, 80, or 100; (2) the 5-year survival probability from any age; (3) the probability of surviving beyond age 70; (4) the median survival time, that is, the time at which half of the hypothetical cohort will have died and beyond which half will continue to live; and (5) the conditional probability of living to age 65 given one has already lived to age 40. Depending on the context, any of these figures may be of greater interest or importance than the LE at a given age; however, LE is the most often cited

<sup>1</sup> For full disclosure, we acknowledge that we, the authors of this chapter, have provided expert opinions on behalf of both plaintiffs and defendants in such legal cases, and will undoubtedly do so in the future.

summary measure of survival. For further details about the columns of the life table and their inter-relationships, the reader is directed to the many references included below [2–6].

#### 2.2. Survival curves

We now focus on age and the column l(x) of Table 1. If we divide the figures in the l(x) column by the radix of the table (l(0) = 100,000), we obtain the probability of survival to each age. Figure 1 plots the resulting survival probabilities against age, the survival curve corresponding to the full US life table (males and females combined).

The unabbreviated version of the life table [2] and the corresponding survival curve (Figure 1) provide essentially the same information. The area under the survival curve equals the LE calculated in the life table; if a line vertical line is drawn at any given age in the survival curve figure, the area under the curve (and bounded by the x- and y-axes) from that point to the right will be the life expectancy at that age. In Figure 1, the area under the curve from age 70 to age

> 110 (the end of the figure) has been shaded. If one counts the shaded rectangles (and fractions thereof) and divides by the probability of survival to age 70 (0.78308), one will find a number close to the e(x) number for age 70 in the life table, namely 15.6 remaining years (which would

> Figure 1. Survival curve for the US GP, 2013. Total area under the survival curve is equal to the life expectancy at birth. Area under the curve from age 70 (shaded in yellow) is estimated by T(70) ÷ 100,000 in the life table, 1,220,609 personyears ÷ 100,000 persons = 12.2 years. This can be estimated in the figure by counting rectangles in the shaded area. This area, normalized by dividing by the probability of survival to age 70, 0.78308, is equal to the life expectancy at age 70:

Survival, Mortality, and Life Expectancy http://dx.doi.org/10.5772/intechopen.80293 49

This connection between the life table and the area under the survival curve gives a way to visualize the implications for life expectancy of evidence provided in many studies of CP survival. Figure 2 provides a hypothetical, but typical, survival curve for children with relatively severe CP

Figure 2. Survival curve for US GP (green) and a cohort with relatively severe CP (orange), from age 5 to age 35. The area under the CP survival curve must clearly be less than that under the GP curve, even if we extend the curves to ages above 100. Methods for extrapolating the CP curve to old ages have been discussed and tested in the literature [3, 5–7].

be to age 85.6).

12.2 years ÷ 0.78308 = 15.6 remaining years.


Table 1. Life table of the US general population, 2017 [2].

summary measure of survival. For further details about the columns of the life table and their

We now focus on age and the column l(x) of Table 1. If we divide the figures in the l(x) column by the radix of the table (l(0) = 100,000), we obtain the probability of survival to each age. Figure 1 plots the resulting survival probabilities against age, the survival curve corresponding to the full

The unabbreviated version of the life table [2] and the corresponding survival curve (Figure 1) provide essentially the same information. The area under the survival curve equals the LE calculated in the life table; if a line vertical line is drawn at any given age in the survival curve figure, the area under the curve (and bounded by the x- and y-axes) from that point to the right will be the life expectancy at that age. In Figure 1, the area under the curve from age 70 to age

Age l(x) d(x) q(x) m(x) L(x) T(x) e(x) 100,000 596 0.006 0.0060 99,702 7,882,920 78.8 99,404 42 0.000 0.0004 99,383 7,783,218 78.3 99,362 25 0.000 0.0003 99,350 7,683,835 77.3 99,337 18 0.000 0.0002 99,328 7,584,486 76.4 99,318 16 0.000 0.0002 99,311 7,485,158 75.4 99,303 14 0.000 0.0001 99,295 7,385,847 74.4 99,288 13 0.000 0.0001 99,282 7,286,552 73.4 99,275 12 0.000 0.0001 99,270 7,187,270 72.4 99,264 10 0.000 0.0001 99,259 7,088,000 71.4 99,254 9 0.000 0.0001 99,249 6,988,742 70.4 99,244 9 0.000 0.0001 99,240 6,889,493 69.4 98,953 70 0.001 0.0007 98,918 5,898,013 59.6 98,062 105 0.001 0.0011 98,009 4,912,689 50.1 96,811 165 0.002 0.0017 96,729 3,937,892 40.7 94,352 390 0.004 0.0041 94,157 2,980,312 31.6 88,788 785 0.009 0.0089 88,395 2,061,381 23.2 78,308 1475 0.019 0.0190 77,570 1,220,609 15.6 57,879 2854 0.049 0.0506 56,453 528,563 9.1 24,208 3443 0.142 0.1534 22,486 110,867 4.6 100 1971 703 0.357 0.4411 1620 4540 2.3

inter-relationships, the reader is directed to the many references included below [2–6].

2.2. Survival curves

48 Cerebral Palsy - Clinical and Therapeutic Aspects

US life table (males and females combined).

Table 1. Life table of the US general population, 2017 [2].

Figure 1. Survival curve for the US GP, 2013. Total area under the survival curve is equal to the life expectancy at birth. Area under the curve from age 70 (shaded in yellow) is estimated by T(70) ÷ 100,000 in the life table, 1,220,609 personyears ÷ 100,000 persons = 12.2 years. This can be estimated in the figure by counting rectangles in the shaded area. This area, normalized by dividing by the probability of survival to age 70, 0.78308, is equal to the life expectancy at age 70: 12.2 years ÷ 0.78308 = 15.6 remaining years.

110 (the end of the figure) has been shaded. If one counts the shaded rectangles (and fractions thereof) and divides by the probability of survival to age 70 (0.78308), one will find a number close to the e(x) number for age 70 in the life table, namely 15.6 remaining years (which would be to age 85.6).

This connection between the life table and the area under the survival curve gives a way to visualize the implications for life expectancy of evidence provided in many studies of CP survival. Figure 2 provides a hypothetical, but typical, survival curve for children with relatively severe CP

Figure 2. Survival curve for US GP (green) and a cohort with relatively severe CP (orange), from age 5 to age 35. The area under the CP survival curve must clearly be less than that under the GP curve, even if we extend the curves to ages above 100. Methods for extrapolating the CP curve to old ages have been discussed and tested in the literature [3, 5–7].

from age 5 to 35 years. On the same figure, we include the corresponding GP survival curve over the same ages. One can immediately see that the area under the CP curve has to be less than that below the GP curve, and this would be true even if both curves extended to ages over 100 years. Published studies of survival of CP (or almost any medical condition) provide estimates of survival across a limited age span - but survival to all ages is needed to estimate life expectancy. Thus some method of extrapolating information to ages 100 or beyond is necessary to use such empirical evidence to estimate life expectancy.

It has long been understood that voluntary physical activity helps promote health and longevity, and that, conversely, a sedentary lifestyle leads to elevated risk of morbidity and mortality [8–13]. The negative consequences of involuntary inactivity, after injury, illness, or surgery, have also been documented [14]. That the limitations in volitional gross motor functioning that often manifest in persons with CP might negatively impact survival and life expectancy should therefore come as no surprise. Nevertheless, clear evidence of this association for CP and other encephalopathies affecting gross and fine motor functioning was not published before 1990. In 1990, a Special Article published in the New England Journal of Medicine reported on the life expectancy of severely neurologically disabled people [15]. Drawing on the recent work that had identified severe intellectual disability (or mental retardation, as it was called at the time) as a marker for mortality rates far exceeding those of age- and gender-matched GPs [16], the study provided life tables stratified by level of disability. For the first time in a major medical journal, level of gross motor functioning emerged as a profound indicator of elevated mortality risk: Life expectancy for immobile children were reported to be less than 10% of age-matched GP life expectancy, and less than 20% that of ambulatory children with comparable levels of intellectual disability. Unfortunately, the article had a serious flaw that rendered all actual life expectancy figures too low, and all mortality rates too high by something on the order of a

Survival, Mortality, and Life Expectancy http://dx.doi.org/10.5772/intechopen.80293 51

Subsequent evaluations of life expectancy of CP specifically based on the same source of data (but without errors of arithmetic) have subsequently been reported and have confirmed what was perhaps the primary finding in the NEJM Special Article: life expectancy varies on a seeming continuum with level of independent gross motor functioning. Evidence in support of this hypothesis is abundant now, coming from numerous countries around the globe. Examples are easily found in the references at the end of this chapter. A summary of life expectancy estimates per se will be found in a recent review of literature from 1990 to 2014 [7]. Life expectancy for young children range from as low as 15 remaining years for those with little or no purposeful gross motor functional ability, to nearly as high as that of their peers in the GP for those who are able to walk without difficulty (and who have no other significant

In published studies, the ability to dress independently and to feed oneself have served as surrogates for overall fine motor functioning, and the connection to longevity is again straightforward: The greater the independent abilities in these areas, the longer the life expectancy. Numerous studies from California have focused on feeding ability [17–21]. Studies from England have focused on combinations of self-feeding and dressing abilities [22–27], and one study from Israel accounted for independent/non-independent feeding ability [28]. The association of mortality risk with fine motor functioning is not nearly as strong as with gross motor functioning, and a number of studies have not addressed this factor at all. Thus, if one is able to account for a specific category of gross motor functioning, a further adjustment for precise levels of fine motor functioning would be expected to have a smaller impact, all else being

factor of 3.

equal.

comorbidities related to their CP).

3.2. Fine motor functioning and feeding ability

An in-depth explanation of the issues involved in such extrapolations is beyond the scope of this chapter. Descriptions and comparisons of various methods may be found in the references cited below [3, 5–7]. In the next section, we review the factors that have been shown to be strongly associated with long-term survival in CP.
