Mortality

Mortality

The number of deaths taking place in a given interval in a specific population.

Mortality Paradox

The phenomenon where women live longer than men but experience higher rates of disability, morbidity, and poor health.

Crude Death Rate (CDR)

• The number of deaths in a given interval (a year) divided by the midpoint population

• Influenced by age & sex structure

• CDR = D/P * 1000

Mortality Measure

• Vital statistics—deaths (numerator)

  • Death certificates

• Census—population at risk (denominator)

Age-Specific Death Rates (ASDR)

• The number of deaths in a given interval to persons of a given age divided by the mid-interval population at risk in that same age category

• _nM_x = _nD_x/_nP_x * k

• Typically correlated across ages within a country

• Generally a J or U shaped curve

ASDR Graph

• J or U shaped curve

• The very young and the old have the highest death rates

• Cause of death varies by age

Population Composition and CDR

• More women drag the CDR down (lower death rates for women)

• Urban and Rural Differentials

• Neighborhood Inequalities

• Educational Differentials

• Social Status Differentials

• Race and Ethnicity Differentials

• Marital Status

Mortality - Urban & Rural Differentials

They differ in jobs, health care access, transport, emergency response time, environmental exposures & local disease pattern. Rural areas can face higher mortality from causes like cardiovascular disease, accidents & influenza/pneumonia, partly because services are farther away & populations are older or more dispersed. At the same time, cities can have their own risks, including pollution, crowding, violence & some chronic disease burdens.

Mortality - Neighbourhood Inequality

Neighbourhoods influence mortality through housing quality, safety, pollution, food access, social cohesion & the availability of clinics, schools & good jobs. Low neighbourhood socioeconomic status has been linked to higher risk of premature mortality, & this appears to matter across the life course rather than only in adulthood. In practice, living in a disadvantaged area can increase stress & reduce access to timely prevention & treatment.

Mortality - Education Differentials

Strongly tied to mortality because it affects income, employment, health literacy, problem-solving skills, & the ability to navigate health systems. Mortality advantages from education are larger when less-educated adults have weaker access to jobs & income, which means local labor-market conditions can amplify or reduce educational gaps. Education also shapes health behaviours & long-term life chances, so it works both directly & indirectly.

Mortality - Social Status Differentials

Higher status usually brings more money, stability, power & control over daily life, all of which protect health. Lower status is associated with more chronic stress, worse working conditions, less access to care & fewer buffers against illness. Wealth & other forms of socioeconomic advantage can therefore translate into lower mortality, sometimes even more strongly than education or income.

Mortality - Race & Ethnicities Differences

Influence mortality through structural racism & unequal access to resources, not biological difference. Segregation shapes who gets safe neighbourhoods, quality schools, stable jobs, insurance & good medical care, which then affects survival.

Mortality - Marital Status

Marriage → lower mortality rates (two incomes) more benefit for men (less risks taken and more frequent doctor visits/check ups)

Cause-Specific Death Rates (CSDR)

• Measures deaths from a specific cause per 100,000 population during a given time

• D_c/P * 100,000​

• Not strictly population at risk

• Typically calculated by age and sex

  • Age−sex specific cirrhosis death rates

  • _nASDR_xm^c = _nD_xm^c /_nP_xm * 100,000

  • n = number of years/period

  • _nD_xm^c = number of males aged x to x+n who died of cirrhosis

  • _nP_xm = number of males aged x to x+n in the population

Mortality Ratios

• Measure of differential mortality by category

• Ratio of rates

• Ex: excess mortality ratio of liver disease by sex

  • % by which male rate is different from female rate (m:f)

  • <100 higher mortality for females in that age group

  • >100 higher mortality for males in that age group

Infant Mortality Rate (IMR)

• The number of infant deaths in a given year divided by the number of live births in the same year

• IMR = D_0z / B_z * k

• D_0z = number of deaths to children under age 1 in year z

• B_z = number of live births in year z

• Higher proportion of infant deaths in the early months

Early Neonatal Mortality

Deaths that occur between birth & the end of the first week of life. Endogenous deaths.

Late Neonatal Mortality

Deaths that occur from the eighth day after birth to the end of the twenty-seventh day after birth. Endogenous deaths.

Post-Neonatal Mortality

Deaths from the twenty-eighth day after birth to the end of the first year. Usually exogenous deaths (caused by something outside of the infant).

Low Infant Mortality vs. High Infant Mortality

• Low Infant Mortality: usually early & late neonatal deaths (endogenous)

• High Infant Mortality: usually post neonatal period deaths (exogenous)

Life Expectancy

• Average age person would live to/die at if they lived their life exposed to current ASDRs for their entire life

• e₀

• Calculated from life table

• Not influenced by age structure

• Analogous to TFR (in that it is quite hypothetical)

Life Table

The table we put age-specific death rates in to figure out what life expectancy is.

Infant Mortality & Life Expectancy

• Highly influenced by infant mortality

• High infant mortality → short life expectancy

• e₅ = life expectancy at age 5 (average additional number of years someone who survived to age 5 can expect to life - if they experience the current ASDRs for their entire life)

Mortality Decline

• Shift from high and young mortality to lower and older mortality

  • Life expectancy (e₀) approaching biological maximum

• Causes of death change as mortality decreases

• Epidemiological transition (Omran 1971, 1981)

  • Three major stages

Epidemiological Transition (Omran)

A theory describing the long-term shift in mortality and disease patterns, where pandemics of infectious disease are gradually replaced by chronic, degenerative, and man-made diseases as the primary cause of death.

Stage 1: The Age of Pestilence & Famine

• 10,000 years ago till the Industrial Revolution

• High & fluctuating mortality

• Infectious & parasitic diseases were the main causes of death as well as wars, famine & urban penalty (too many people in the same area → easier transition of diseases)

• Life expectancy at birth was between 20 to 35 years

• Women in their adolescent and reproductive years were at higher risk of death (maternal death) than were men but at lower risk in older ages

• Female remains of that era indicate higher frequencies of bone loss and nutritional anemia (Barrett et al. 1998)

Stage 2: The Age of Receding Pandemics - Early Phase

• Mid 1700s to early 1900s

• Causes of death similar to Stage 1

• Rising life expectancy: e₀ = 45-50

• High infant & child mortality (but with major improvements)

• Women were still at high risk of dying in adolescent and fertile years (higher risk than young men)

• Economic changes taking place (agricultural practices & early industrialization)

Stage 2: The Age of Receding Pandemics - Late Phase

• Declines in epidemics & other infectious diseases

• Infection leading cause of death still (degenerative diseases become more significant)

• IMR declines

• End of urban penalty

• Increased life expectancy at birth through the creation of healthier conditions (advances in sanitation and hygiene, greater availability of food and better nutrition) → women’s mortality in reproductive ages declines

Stage 3: The Age of Degenerative & Man-Made Diseases

• Early 1900s to WWII

• Overall mortality declines (longer life expectancy e₀ = 70)

• Significant IMR decline to <25/1000 births

• Maternal deaths fall significantly

• Leading cause of death → degenerative diseases

• Wealthy countries: economic growth & scientific advancements → improved public health, nutrition & medical technologies

• Poor countries: medical technologies was the driver for the transition (post WWII)

• Smaller families allowed women to strive for more options in their social roles including higher education and careers

Omran vs. Barrett et. al

• Omran: 2nd & 3rd Stages

  • Focus on European & US experience

  • Distinguished by dominant cause of death

• Barrett et al.: Second Epidemiological Transition

  • Includes Omran’s 2nd & 3rd Stages

  • Incorporates experiences of low- and middle-income countries

Epidemiological Transition - Criticisms

• Incomplete (ends in the 1960s) → attempts to extend the framework

• Unidirectional in its assumptions (specific path that countries/populations will go through)

• Focus on mortality: mortality vs. health/morbidity (how long people are living)

• Similar to DTT: reliance on modernization, there can be improvements in health without modernization

• Variance within a country:

  • Different transitions for males & females

  • Role of society or culture & inequality (inequalities/poor infrastructure support communicable disease mortality)

Stage 4: The Age of Delayed Degenerative Diseases (Olshanksy & Ault 1986)

• Continuation of mortality declines & its eventual approach to stability at low levels

• Dominance of degenerative disease mortality

• Delayed onset of disease

• Further rise in life expectancy e₀ > 70

Stage 4: The Age of Man-Made Diseases/Hybristic (Rogers & Hackenberg 1987)

• Increasing prevalence of diseases linked to lifestyle & health behaviours

  • Obesity/diet & exercise, alcohol & drug use

  • Accidents (firearms, driving, etc.)

  • Infectious diseases (sexually transmitted)

• Further rise in life expectancy e₀ > 70

Difference between US IMR & Other Countries

• Data comparability (the way live births/gestational age/birth weight are defined varies across countries)

• Conditions at birth

Finnish Infant Cardboard Boxes

• Sign up for the program to get the boxes

• Program running for more than 80 years

• The boxes include items for babies such as clothes & items for mothers such as sanitary pads

• Program incentives women to participate in the health program (prenatal care)

• After baby’s birth a nurse checks in for follow ups

IMR in the US by Ethnicity of Mother

• Driven by the experiences of disadvantaged mothers rather than wealthy mothers

• Most disadvantaged mothers: Black women and then native Americans

Concerns with Measuring Infant Mortality

• Seasonal variation (holiday seasons tend to increase birth rates)

• Babies are under-enumerated in censuses and surveys

  • Babies can be born and can die in the same year or before data collection

  • Often not reported

• Variation in measurement across settings (different definitions)