Factors Influencing retention of Health Workers in Primary Health Care Facilities: A Case of the Kakamega County

LECTURE FOUR LEVEL IV MBChBPROF. E.K. MUCHUNGASchool of Public HealthUniversity of Nairobi

THE LIFE TABLES

GoalTo define the life tables, outline types of life tables, history, assumptions, anatomy and application of life tables. Definition of Life TablesIs a statistical model that is used to derive some measures of mortality. Though the core function is the measurement of mortality, it is applied in different ways by Public health workers, Demographers, Actuaries to study Longevity, fertility, migration, population growth as well as projections of population size, widowhood, orphanhood and length of married life.

The entire life table is generated from age-specific mortality rate and the resulting values are used to measure mortality, survivorship and life expectancy.

2Definition of Life Tables (Contd)Life tables are one form of combining mortality rates of a population at different ages into a single statistical model. Consequently, the life table is not influenced by the age distribution of an actual population and do not require the adoption of a standard population.

Types of Life Tables

Differences occur due to the (1) Reference year of the table (2). The age details (3) Number of factors in the table.

The Current or Period Life Tables (for a short period of time) Is based on the experience over a short period of time one year, two years or three years during which mortality has remained unchanged.The table represents the combined experience by age of the population in a particular short period of time treated synthetically. Can be viewed as a snapshot of current mortality studied cross-sectionally. The cohort is however, artificial or synthetic that is subject to the Age Specific Death Rate (because ASDR is dynamic) observed in that time period.

The Life Tables (Contd)(2) The Generation Life TablesIs based on the mortality experience by a particular birth cohort. For example, all persons born in 1940, 1950, 1960, 1980 or 1990s. This means observing the mortality experience of the cohort longitudinally from birth till all of them die.Due to challenges in constructing such a table, the table is used for projecting mortality, studying mortality trends and for measurement of fertility and reproductivity.

Complete Life Tables (Unabridged- Full)According to the length of the age interval in which data are presented. In this context, data are presented for every single year of age from 0 to the last applicable age (85 years or so).

The Abridged Life TablesContains data by intervals of five or ten years of age. In most cases, the simpler abridged life table is prepared rather than the elaborate complete life table.

Standard Life TableIs concerned with the general mortality experience of a single cohort by age.

The Life Tables (Cont)Multiple Decrement Life TableDescribes the separate and combined effects of more than one factor e.g. marriage and mortality; occupation and mortality etc. i.e. mortality and another factor

History of Life Tables The earliest life tables originated in Europe around 1662 pioneered by Graunt. The earliest published life tables in 1693 were based on mortality and birth registration data for a single city. Thereafter, other Life Tables began to be published during 17th and 18th centuries as data collection techniques improved.Today, nearly all countries publish elaborate life tables. In USA, life tables have been published since 1900-02 period. Developing countries have had life tables published in Demographic Yearbooks since 1966 (United Nations Population Division) and by authors such as Ansley Coale and Demeny.

In Kenya, the Association of Kenya Insurers (AKI) launched a mortality table for insured lives in the country for the period 2001-2003.

By applying Kenyas mortality table, the country became one of the few in Africa to construct own table using local actuaries led by Alexander Forbes Financial Services the leading firm of consulting actuaries.

In the past, local efforts in constructing own life tables have not been successful due to problems in data collection. This achievement will imply replacing the English Life Tables of 1949-52 and the 1955 annuity tables that are currently prescribed in the insurance act.

Assumptions of the Life TableAs noted earlier, the life table is a life history of a synthetic group or cohort, as it is diminished gradually by deaths.

The record begins at the birth of each member and continues until all members have died.

The synthetic cohort looses a predetermined proportion at each age, and therefore, represents a situation that is artificially contrived. This is accomplished with the assistance of five assumptions. They are:1. The cohort is closed from in and out migration. Therefore, there are no changes in membership except through loses occasioned by deaths.

Assumptions of the Life Table (Contd)2. People in the Cohort die at each age according to a schedule (arrangement) that is fixed in advance, and does not change.

3. The Cohort originates from some standard number of births (set at 100, 1000, 10,000 or 100,000) called the radix of the life table. This standardized aspect facilitates comparison between different life tables. For example, 5420 members of a starting Cohort of 10,000 who survive to exact age 35 means that 54.2% are survivors.

4. At each age except the first year of life, deaths are evenly distributed between one birthday and the next. That is , half of the deaths expected between ages 9 and 10 will occur by the time everyone reached 9 years and so on.

5. Finally, the Cohort normally contains members of only one sex. It is however possible to construct a life table for both sexes, but the differences between male and female mortality at all ages are sufficient to justify treating them separately.

Just like in an actual situation, a life tables looses a great many of its original members at a very early age when deaths are relatively frequent.

Anatomy of the Life TableEvery value in the table refers to some particular age. Life Tables represent the effects of mortality by age on the size of a synthetic Cohort without the interference of the complicating factor of the actual world.

The basic life table functions - qx, lx ndx, nLx, Tx and eox are generally calculated and published for every life table (6 columns in all). However, due to limitations of space, some of the columns may be omitted. For example, Demographic Yearbooks publishes only qx, lx and eox without a significant loss of information since the functions are interrelated.

The Life Tables x to x+n is simply the exact period between two ages e.g. 20 25 means the five year interval between 20th and 25th birthdays.n stands for the width of a time interval. Exact age 0 and exact age 1 equals 1 year. Exact age 1 and exact age five equals 4 years and so on.nqx = the probability of dying between x and x + n.The opposite the probability of surviving is npx (where p+q = 1)(v) lx = the number of persons living at the beginning of age interval x out of a total number of births assumed as the radix of the L.T. For example, out of 100,000 newborn female babies in England and Wales (1985), 98, 692 survived to exact age 20.

The Life Tables (Contd)(vi) ndx - Is simply the number of persons who would die within x to x + n out of a total number of births assumed in the life table. Example, 825 persons would die between exact age 0 and exact age 1 in the England & Wales L.T. cited earlier.

(vii) nLx The number of person-years that would be lived within the indicated age interval x to x+n out of the radix.

The Life Tables (Contd)For USA, 96111 persons would survive to exact age 20. 95,517 would survive to exact age 25.

We take the later figure (95,517 and multiply by 5 (5 year age interval) = 477,585 to get the person-years lived

Those who died between 20th and 25th birthdays were 594 persons. Applying the assumption of deaths being distributed between are birthday and next, we conclude that on the average, those who died lived 2.5 year or half the time period. Add this to 477,585 = 479,070.

Tx. The total number of person-years that would be lived after the beginning of the indicated age interval by the Cohort of 100,000 births assumed. In our England and Wales example, person-years lived from 0 until 85+ would be 7,756,261. However, the technique of computing person years lived is bottom up using nLx.

eox The best known function is simply the average remaining life time in years for a person who survives to the beginning of the indicated age interval. This function is also referred to as the complete expectation of life or simply life expectancy. In our example, a person who had reached her 20th birthday should expect to live 58.542 years more, on the average.

Note that e is often written with a superscript eox. This is to distinguish if from e the base of natural logarithms.

Table 1: Simple Life Table Quickly calculate and enter the missing data in columns 2 and 3123Xnqxlxdx012345+0.004600.02310.01290.00650.0044100,000

COUNTRY Y 2010

123456x to x+nnqxlxndxnLxTxeox0-11-55-1010-1515-2020-2525-3030-3535-4040-4545-5050-5555-6060-6565-7070-7575-8080-8585+0.01470.0270.00170.00180.00510.00670.00660.00700.00970.01510.02380.03700.05530.08540.11680.17550.26360.36121.000100,00025,90525,905175,915175,915Short Answer Questions1. Fill in the missing data for Country Y above2. Is Country Y a developed or developing Country?3. Provide evidence to support your answer in 2 above.Life TablesLife Table Interrelationships of functionsAll functions in a life table are dependent on one another, but often the qx is regarded as the most independent of all functions Indeed, the mortality rate (nqx) is the initial function from which all other life table functions are derived.-eox = Tx lx-Tx = eox .lx

-5 lx = Tx Tx + 5

-dx = Lx. qx

Life TablesBasic data for current life tables is the census or an accurate estimate of the population by age and sex. Deaths recorded in the year of the census or the years around the census year as well as births firm the same time period are key to life tables.Life Span and Life ExpectancyIn measuring longevity, two concepts should be delineated i.e. life span and life expectancy. Life span tries to establish the maximum age human beings as a species would attain under ideal conditions. In this context, life span would be defined as the age beyond which less than 0.1% of the original Cohort still survives. Historically, very few people survive beyond 100 years, and as such, life span is recorded as 100 years.Life expectancy is the expected number of years to be lived on the average. Accurate records exist for many countries from which estimates have been prepared on a regular basis.

Life Tables These estimates are derived from a current life table. From these records, it is apparent that longerity has shown considerable improvement in the recent decades. For instance, Kenyas life expectancy that had declined in the 1990s is now 57 years. Among female in Japan, life expectancy is well above 85 years.

Application of Life TablesLife tables can be constructed as a stationary population. This alternative technique of a stationary population is defined as a population whose total number and distribution by age do not change with time. Such hypothetical population could be obtained if the number of births per year remained constant (usually assumed at 100,000) for a long period of time and each Cohort of births experienced the current observed mortality rates throughout life. The annual number of deaths would also equal 100,000. No change in the size of the population.

Application of Life Table Data Human Development Index (HDI)This is a composite index that measures the average achievements of a country in three basic components of human development. These are:A long and health lifeAccess to knowledgeA decent standard of livingThese three dimensions are measured by:Life expectancy at birthAdult literacy and combined gross enrolment in primary, secondary and tertially levels of education.Gross Domestic Product (GDP) per capita in purchasing power parity in US dollars.

Life Tables (Cont)With respect to Kenya, life expectancy at birth varies by provinces, while combining the three indicators reveal that Nairobi has the best human development index.

Secondly, the Kenya National Bureau of Statistics (Statistical Abstract 2009) has published life expectancy in Kenya with and without HIV/AIDS for the period 1980-2010.

For males without HIV, the trend analysis show that there was an upward trend from 58.8 years in 1980 to 64.2 years in 2010. For females, the results were 66.5 years and 71.1 years respectively.

Life Tables (Cont.)However, the trend changes with HIV/AIDS. A slight increase (Males) is evident between 1985-1990, but thereafter, a downward trend between 1995-2000.

Between 2000-2010, an upward trend seem to be emerging. For females, there was a downward trend between 1980 until 2005. Thereafter, an upward trend is evident, though not yet the level seen in 1980-85 period.

Differentials in life expectancy between males and females has narrowed from 8 years (1980-85) to 5.3 years between 2005-2010.

THE END

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