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Chapter 7

SOC312H: Chapter 7.docx

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Brent Berry

Chapter 7: Mortality and Population Health Determinants of Population Health - The population health perspective recognizes the complex interactions of individual and structural factors in determining health, including interplay of individual characteristics (including genetics) with social and economic factors (including culture) and physical environments (ex. Family, neighbourhood, work, the community, and other important spheres of life) o Societal disparity in health are closely related to disparities in income and wealth and health gains can be achieved by focusing interventions not only on entire population but also on disadvantaged minorities within the larger society Demographic and Sociological Dimensions of Mortality - Mortality refers to the number of events (‘deaths’) taking place in a given interval in a specific population - Since death can occur only after a live birth, it doesn’t encompass miscarriage, stillbirth, or abortion - The medial definition of death is quite specific: it is the postnatal cessation of vital functions without possibility of resuscitation; verified in writing by death certificate signed by licensed physician or medical examiner or coroner o Thus a person on life support systems is considered to be alive - White and Preston determined that about half of the current population would never have been born were it not for significant progress in health and disease prevention made in early 1900’s Why Are You Alive? th - ‘half of population owes its existence to 20 century mortality improvements’ - White and Preston reached this conclusion by using counterfactual projections  they set up a what if experiment o Calculated that fully half of people now alive would have died young or would be absent because one of their parents would not have survived to reproductive age o Researchers made great advances in medicine over past 100 years but at least half of us owe our very lives to one big breakthrough: Preston credits acceptance of germ theory of disease and the changes it brought to the practice of medicine, the handling of food, and treatment of water Basic Measures of Mortality Crude Death Rate - CDR: number of deaths in a given interval, usually a year, divided by midpoint population (or an estimate of the midyear population for no-census years; typically expressed per 1, 000 population: o CDR: D/P x 1,000 D is number of deaths observed in interval, and P is midyear population - Demographers commonly compute 2 year average crude death rate to ensure greater stability in measure by eliminating unusual yearly fluctuations in number of deaths: o CDR: (D1 + D2 + D3) / P X 123 Where D1, D2, and D3, represent number of deaths in three successive years, with year two being central year. The population at risk is P2, the midyear population for the central year - The crude death rate simply measures the total number of deaths divided by total population; it is insensitive to effects of age composition, which play an important role in mortality o The fact that the older one is, the greater the chance of dying; and younger one is the lower the risk of dying o Thus some developing countries have lower crude birth rates b/c age compositions are younger than those of more developed countrie o Age structure must be taken into account if we are to obtain clear pic of true level of mortality in a country or any population Age-Specific Death Rate - Age specific death rates helps us to avoid confounding effects of age composition on any cross country comparison of mortality - It is defined as: number of deaths to persons of a given age divided by mid-year population at risk in the same age category; can be calculated for separate age categories - General formula: o M x D x P x 1, 000 where M stanxs for age specific death rate, the letter x indexes a given age category, and terms D and x corresxond to deaths and midyear population for age category x, respectively - CDR and age specific death rates are related: the CDR is cumulative product of a set of age specific death rates and an age distribution for a given population Age Patterns of Mortality: - Difference in age pattern of mortality and level of mortality for a population o The age pattern refers to shape of pattern of death rates over age, while level of mortality corresponds to overall death rate of a population (or some other indicator of mortality, such as life expectancy at birth) - According to age pattern of mortality that is common to all populations, the risk of death is high in first month after birth but declines during rest of infancy and childhood and remains low throughout adolescence; it rises in young adulthood but then stabilizes, increasing only slightly until past middle age, when the risk of death begins to intensify with advancing age o Age pattern of mortality applies across all human populations - Age specific death rates for pre transitional societies tend to follow a U shaped patterns  high mortality in infancy and early childhood, and also in old age o With increasing modernization the incidence of infant mortality declines  helps to produce J-shaped pattern of mortality now common in advanced societies Infant Mortality Rates and its Components - Infant mortality: death occurring between birth and end of first year of life. Subdivided: o Early neonatal mortality: deaths that occur between birth and end of first week of life th th o Late Neonatal Mortality: deaths that occur from 8 day after birth to end of 27 day after birth o Post-neonatal mortality: deaths from 28 day after birth to end of first year - Vital stats agencies in developed countries also collect info on fetal deaths  is the death of a fetus (or product of conception) prior to its complete removal or exclusion from the mother, regardless of length of the pregnancy o Fetal death includes miscarriages, abortions, and stillbirths o Late fetal death: refers to death that occurs late in a pregnancy, usually in 28 th week of gestation or later o Miscarriage is spontaneous or accidental termination of fetal life early in pregnancy o Abortion is any termination of pregnancy =spontaneous or induced –before 28 th week of gestation o An induced abortion is carried out with intention of termination pregnancy; all other abortions are considered spontaneous o WHO recognize spontaneous loss of fetus can occur prior to 28 week ofh gestation, recommends that fetal deaths be classified according to period of gestation during which they occur  Early fetal mortality: occurs prior to 20 week of gestation  Intermediate Fetal Mortality: occurs between 20 and 27 week of th gestation  Late Fetal Mortality: occurs in the 28 week of gestation or later - The infant mortality rate (IMR) is calculated as number of infant deaths in given year divided by number of live births in same year; it is usually multiplied by 1, 000. Thus infant mortality rate of 20 would indicate that for every 1, 000 live births in population, here are 20 infant deaths o IMR = D /0B x 1, 000 where D is0the number of infant deaths in given year, and B is number of live births during the same year o A proportion of infant deaths that occur during a given year are deaths of infants who were born during preceding year and hence are not part of same universe of births used to compute the rate - Worldwide the IMR for 2005 was 54 per 1, 000. Among the more developed countries the rate was just 6 infant deaths per 1, 000 live births; among the less developed countries, the IMRs are about 10 times greater than the average Cause of Death in Infancy - Bourgeois-Pichat proposed that infant deaths can be classified in two major categories depending on whether they are endogenous or exogenous o Endogenous infant deaths are related to complications arising in neonatal period  include congenital anomalies (chromosomal abnormalities, malformations of heart and central nervous system, deformities of the musculoskeletal system, etc.), complications during delivery, and low birth weight. Endogenous deaths stem from complications with newborn’s constitution, they are difficult to control (though advances in medicine are helping to reduce these rates) o Exogenous deaths occur mainly in post-neonatal period. They are strongly associated with external factors or situations in socio-economic environment of the infant, such as exposure to cold or excessive heat, infection, inadequate care, malnutrition, accidents and even violence  Accounts for significant number of deaths to children between ages of 1 and 4, esp. in developing countries  Endogenous mortality rates predominate during first 18 days of life - Once infant mortality rate in a population falls to range of about 20 deaths per 1, 000 live births, infant mortality tends to become less clustered in neonatal period as a result of improved care in prenatal, delivery and postnatal stages - one of three major causes of death in neonates is low birth weight, usually associated with prematurity; diff categories of low birth weight o low birth weight infants: weight at birth falls between 500 and 2, 4999 grams o very low birth weight infants: weight less than 1, 500 grams o extremely low birth weight infants: weight at birth is less than 1, 000 grams Cause-Specific Death Rate - in industrialized countries, two of deadliest killers are heart disease ad cancer although a larger portion of all deaths in these countries can also be attributed to accidents and violence o based on a classification system called international classification of diseases (ICD), which involves a detailed listing of all known diseases and medical conditions that can result in death; each disease or condition is assigned a letter and numerical code - Cause-specific death rate: D / c x 100, 000 where D is dcaths due to a particular disease or ‘cause’ c, occurring in the population during a specified interval, and P is mid- year population exposed to risk of dying from disease or condition c in the interval; the constant 100, 000 is used by convention when computing cause-specific death rates - in some circumstances it may be necessary to compute cause-specific death ratio in form of: o D c D x 100 where the numerator is the number of deaths from a given cause, and denominator is total number of deaths - Cause specific death rate is a measure of incidence (how many deaths from cause c occur per 100, 000 population), the cause-specific death ratio tells us what percentage of all deaths are attributable to cause c o For instance, in Canada, about 37% of all deaths in a given year are due to disease of circulatory system, and about 27% are caused by cancer - The cause specific death rate is really just crude death rate for given cause of death o It can be expanded to include age, sex, and other characteristics The Life Table Basic Description of the Life Table - For demographers, the life table is a tool for describing a population’s mortality using period cross-sectional, age-specific death rates o Describes the survival experience of a fictional (or synthetic) cohort subjected to current age-specific death rates of an actual population over the cohort’s imagined lifetime  referred to as period life table o a cohort (or generational) life table is computed from historical data for a birth cohort that was born many years ago and is not extinct - in technical terms a life table is a hypothetical population of 100, 000 newborn babies, exposed to prevailing age-specific mortality schedule of an actual population o we can trace the lives of the 100, 000 from birth to death and in this way we are able to see how the hypothetical population experiences age-specific probabilities of death and survival as it passes through age and calendar time o life table was introduced by John Graunt in natural and political observations made upon bills of morality (1662)  number of deaths by age - most frequently used measures derived from life table is life expectancy,  average number of years of life remaining for someone aged x, where x may represent any age category in life tale from birth to some upper limit Assumptions of the Life Table - 1. the life table is a hypothetical population that is closed to migration; as a result, births and deaths are the only demographic processes in this population - 2. Because life table doesn’t take migration into account, the crude death rate and the crude birth rate are identical in this population and therefore rate of natural increase will always be 0, because 100, 000 people are born and the same 100, 000 people eventually die). The life table is thus a stationary population, meaning that it has a stable, unchanging annual age specific mortality rats, with unchanging number of births (ie, 100 000) - 3. The number of births in life table population is conventionally set at 100, 000 this is called the radix of the life table - 4. The birth cohort of 100, 000 dies according to predetermined schedule of age specific death rates, taken form actual population - 5. In most practical cases, it is assumed that the distribution of death is uniform within every age category except for infancy, early childhood, and very old age, where the distribution of depths is clearly not uniform Life Table Functions - Age-specific death rates are used to generate the life table - Once we have compute age specific death rates for a population (m ) we canxderive a number of life table functions (pg. 266-67 for formulas) Mortality Change Through History - Dramatic increases in l.e over course of 20 century can be attributed to fact that degenerative causes of death have largely replaced deaths caused by infectious and pathogenic diseases Epidemiological Transition - According to Omran’s theory, societies as they modernize experience a gradual change in their patterns of disease and mortality o Typically they move from long period in which infectious and parasitic diseases along with famine, pestilence and war are the dominant agents of premature death, to a stage in which chronic and degenerative diseases (such as cancer and heart disease) become the leading killers o Identified 3 stages  The age of famine and pestilence (prehistory to c. 1750)  The age of receding pandemics (c. 1750 to the early 1920’s)  The age of human-made and degenerative causes of death (early 1920’s to the 1960’s) • The standards of living thesis: McKeown ‘s analysis of historical data for England and Wales les him to series of interesting conclusions, which form the basis of the standards of living thesis: th o 1. Declines in mortality during 18 and early 19h centuries were associated primarily with decline in deaths form infectious diseases and secondarily with decrease in deaths from non-infective causes, infanticide and starvation o 2. Although some infectious diseases declined as result of change in relationship between organism and host, this alone cannot account of enormous reduction in mortality and growth of population during this time o 3. Mortality was greatly affected by immunization before 1935. The decrease in deaths from infections with effective medical treatments before 1935 made only small contribution to decline in deaths after 1938 o 4. Given second and third conclusions, the only other explanation for reduction in mortality is improvements in socio-economic environment o 5. In second half of century, new hygienic measures led to substantial reduction of mortality from intestinal infections o 6. Most acceptable explanation for reduction of mortality and growth of population that preceded advances in hygiene is an improvement in nutrition due to greater food supplies o Decline e of mortality form non-infective causes (infanticide and starving in 18 and 19 centuries and large number of conditions in the 20 ) was due mostly to contraceptive use and improved nutrition. In particular, new measures designed to avoid wanted pregnancies likely played greatest role in decrease of deaths from non- infective conditions Extensions to Epidemiological Transition The Age of Delayed Degenerative Diseases th - Olshansky and Ault  Advanced society is now in a 4 stage of epi. Transition, the age of delayed degenerative diseases o Characterized by continuing slow and often fluctuating mortality declines, which are increasingly concentrated in later stages of life, and a variable patterns of change in the average onset and duration of major chronic ailments, notably cardiovascular disease and to less degree, cancer o Chronic and degenerative diseases continue to dominate, but onset of major disability form diseases is occurring later in life The Hybristic Stage - Rogers and Hackenberg, post-industrial societies have entered a hybristic epidemiological sage, characterized by a prominence of both chronic and communicable disease, which in combination account for an increasing portion of deaths - Evidence  real causes of death today are related mainly to lifestyle behaviours that compromise good health and longevity, specifically smoking, overeating, maintain an unhealthy diet, and avoiding exercise - Two sets of authors differ mainly in emphasis: Olshansky and Ault emphasize chronic and degenerative diseases and improved survival rats in older ages, while Rogers and Hackenberg stress importance of lifestyle factors and individual behaviours as causes of premature death Exceptions to Epidemiological Transition Theory - Decreased mortality results from socioeconomic advancement, because modernization paves eh way to better health care and public health systems. These studies have found that in some poor countries major health improvements are possible without large scale economic growth - Another flaw is its implicit assumption of a linear and irreversible progression through the various stages  there a number of cases of retrogressions in mortality improvements, ex. Former soviet Bloc countries which have seen reductions in life expectancy over recent decades - According to epi. Transition theory, infectious diseases are supposed to play a minor role in mortality during most advanced stages of epi. transition. Yet in recent years the world has seen the emergence of lethal new viruses that pose serious threats to population health (ex. reappearance of HIV/AIDS in developed countries in early 1980’s) - Another problem with theory is applied assumption of homogeneity in health conditions of population within any stage of epidemiological development  fails to allow for possibility of health and mortality inequalities among disadvantages subpopulations whose overall health lags far behind that of larger society such as first nations in Canada The Puzzling Origins of AIDS (pg. 274-275) - The Tainted Polio Vaccine - The Cut-Hunter Hypothesis - The Contaminated Needles Theory - The Heart of Darkness Thesis Health Transition - Describes the improvements in life expectancy and overall health of populations over the historical spectrum, going beyond the scope covered by epi transition theory - Concentrate on explaining how the health of a population changes as a result of change I social organization, environment, health care situations and prevention systems, as well as genetic biological factors, lifestyles and behaviour and culture - Several interacting sets of factors
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