DEMOG 130 : MIDTERM 2

What is the difference and similarity between (mx) and (ux) and what is (lx)

mx: discrete death rate among people alive at age x

ux: continuous smoother, of death among people alive at age x.

both represent mortality rates.

lx - survival curve

• how many ppl alive at age x

mx derivative of lx

Frailty

Mortality selection

Mortality displacement (harvesting)

hidden differences in risk between people

frail people die first
deaths shifted earlier

Climate → Environment → Exposure → Health outcome
give example for each

• Climate: heat

• Environment: more pollution

• Exposure: breathing PM2.5

• Outcome: heart disease

sources of water contamination (4)

• sewage failure

• industrial sites

• flooding

• saltwater intrusion

why is population mortality not the same as individual mortality

bc of frailty (heterogenity)

What is a J curve? Why?

Mortality over age looks like J shape (old ppl die a lot more and newborn too)

• a mathematically produced curve shaped in J

• that shows population mortality. even if no single person has a j curve risk

• PROVIDED THAT THERE IS INDIVIDUAL VARIATION IN FRAILTY

*****

because of heterogeneity (ppl are diff from each other.)

excess mortality vs official counts

official estimates undercount the disaster deaths.

excess mortality in 2025 fire were estimated at 10x greater then the official count.

why do we care about life years lost, and what is it

the shift from life years lost counts for the premature mortality and how it impacts the younger generations dying

what type of problem is tuberculosis & why?

both a societal and a bacterial one.

thi sis because it thrives in poverty, displacement and healthcare systems.

what is drug resistant tb (MDR-TB)

it’s a man-made crisis which is caused by inconsistent treatment access in global health.

what is a virtuous cycle

investing in healthcare infrastructure can help a create a cycle that helps society resist future diverse health threats.

Fundamental Cause Theory

socioeconomic resources are fundamental causes that stay the same BUT THE MECHANISMS CHANGE OVER TIME, which lead to health outcomes because they allow people to avoid risks( such as wealth)

Tuberculosis: john green says it is societal one not just bacteria

why does climate change impact poor areas more?

causes more deaths bc while humans can adapt, it is not feasible for poor populations since they do not have access to money to get AC systems in their actual house.

What is extreme temp and rainfall linked to in human interactions?

super hot temp increases conflict, and economic collapse.

what is air pollution PM and what does it do

its PM 2.5, super tiny. this triggers inflammation and chronic disease.

what is an example of how air pollution impacts a country

in China, the people above the geo-line who got free coal, river policy led to the significant drop in life expectancy for those above due to pollution from the coal.

scarring vs selection. explain each

scarring : the long term negative impacts on survivors

example: tsunami survivors HPA axis is burnt through, causing to be in a stress state for years after the accident.

selection: the process where the weakest die, leaving the “healthy”to survive.

example: indian ocean tsunami : physical strength required to survive so there was more deaths in kids and older people.

what is mortality displacement

the theory that extreme weather only kills those near death already but this is false! there are many extra deaths that would not have occurred otherwise. : proven by the french 2003 heatwave

what do authors use in other to rule out bias

they use placebo tests which run on same analysis on a group where they expect a null result.
if placebo shows no change, it stronger argument that disaster was true cause.

what is difference in differences

used to estimate disaster impacts. ex: how fertility increases after tsunami
- by comparing the area that is undamaged and damaged.

what is a fixed effect model

they subtract out the confounding variables that are stable over time or across locations to isolate the effect of climate variable.

what is the PICO framework?

u use it to turn a vague idea into a answerable research question.

Population- who are you studying (people in california)

Independent Variable-what is the cause (prx to wildfire)

Comparison- what are you comparing to (women in arizona)

Outcome-what is specific health result

what is a compounding disaster

when two disasters are happening at the same time.

such as a hurricane during a heatwave. which makes it harder for teams to respond to help those in it.

what is managed retreat

the planned relocation of communities that are away from water flooded areas.

what is Vertical Land Motion (VLM)

its a key predictor of sea-level rise risk. some areas are sinking while others land is rising.

New Orleans is sinking due to sediment compaction..

• so sea level is rising and much faster

Albany, slightly rising in some ares but more stable.

SIR MODEL. What is the U curve

susceptible, infected, recovered. when all the people in population get infected or recovered, nobody new to infect.

how do births replenish susceptible populations

in a model with no births, the epidemic dies out since everyone is all done and either infected or dead. this leaves a U curve.

what is relic pollution

refers to the industrial waster like lead or arsenic that is buried in old soil, but it comes out when there is a flood. there are 6k sites that are at risk of flooding currently.

what is frailty

the unobserved variation in death risks. some people are frailer then others

what is harvesting

a myth that says that the heatwaves or disasters only speed up deaths of people at end of life.
- harvesting tests would check if death drops after spike but maybe its just timing shifts.

what are lx and mx columns?

how much was excess mortality estimates from the 2025 LA wildfire?

more than 10

what has to be true about a population in order to create a J curve?

there must be individual variation in the level of mortality risk.

how could it be possible that a huge disaster have impacts on mortality but not morbidity?

because of selection and scarring working in opposite directions.
selection is the most vulnerable people dying so survivors look healthier

scarring is the survivors health being worse.

might change bc they cancel out kinda.

mortality from air pollution PM 2.5 is expected to increase in southeast asia and india because of

populations in these areas are aging faster and the health of older people is particularly vulnerable to that pollution

the figure of rubella and measles shows..

hese relationships are typically nonlinear small drops in vaccination can lead to large increases in disease once you pass a threshold.

and

Measles requires higher vaccine coverage for herd immunity than rubella because it’s more contagious.

What is R0 and why is it related to herd immunity?
- why is it related to the shape of relationship between vaccine coverage and incident infectious disease cases

Average number of people one infected person will infect in a fully unprotected population.

Herd immunity happens when enough people are immune so each case spreads to less then 1 person

affects shape:

• relationship nonlinear, when coverage is high, cases stay low.

• once you drop below herd immunity, cases jump very fast.

two way fixed effect

a regression specification model that adjusts for any feature of geographic region that is

stable over time whether or not it can be measured

it controls for time differences and common shocks across time.

• removes a constant place in time and anything affecting lal places at the same time. IN ORDER TO ISOLATE: CLIMATE CHANGE

why is it valuable to adjust for unmeasured characteristics of regions and time periods when studying climate effects on health outcomes?

it helps get a cleaner causal effect. sometimes regions differ in healthcare, culture, health.. and time periods have diff things like tech, pandemics etc.

adjusting removes hidden bias, shows true effect of climate on health outcomes.

what is the shared socioeconomic pathway and how does it help us

they are scenarios about how the world may develop in the future.

gives us a possible future idea, lets researchers predict climate and health impacts under a scenario and helps policymakers plan depending on outcomes.

death augmented by deaths impact on survivors. therefore, what do we see low levels of in popilations that go through disasters?

low orphanhood bc not likley that a child survives and a parent does not.

 What dimension of coastal areas will make sea level rise over the next five decades riskier

for Gulf Coast regions of the U.S. relative to many coastal parts of California?

vertical land motion

A large fraction of mortality attributable to water system contamination is caused by

diarrheal disease… bc of pathogens in unsafe drinking water

Crude Death Rate

Calculated as Deaths / Mid-year population size.

Modal Age of Death

Even in high-mortality populations, the most common age of death is often in the 70s

Sea Level Rise numeric estimates

1 in 50 people and 1 in 35 properties in 32 coastal U.S. cities.

how to manage the risks?

climate hazard reduction

adaptation of exposure reduction
adaptation of vulnerability reduction

How many people will need to relocate by 2050

more than 300 million ppl will need to relocate by 2050

how common are natural disasters

1 in 4 poeple globally affected by one in the last 5 years
1 in 3 in southeast asia

Incidence vs Prevalence

• Incidence : how many new cases in a defined period of time

  • HIV peaked at different places in time. 

• Prevalence: how many people have the condition overall. 

  • The prevalence of HIV is going up because of increases in survival rates.

  • You can recover from HIV.

drivers of disease

• Environmental: Weather (humidity/temp) affects how long a virus survives in the air.

• Demographic: Births "replenish" the susceptible pool.

• Public Health: Vaccines or quarantine measures.

• Socioeconomic: Overcrowding or poverty levels.

why Age-Distribution Matters

If a population is "aging" (more people over 65), climate-driven mortality will look much higher because air pollution and heat predominantly kill the elderly.

Micro vs. Macro

• Micro: Looking at individual people (how one person reacts to heat).

• Macro: Looking at a whole country's GDP.

• The Nonlinear Effect: Economic productivity stays fine until about 20–30°C, then it falls off a cliff.

Missing Data & Vital Registration

• The Gap: Less than 1/3 of the world lives in a country that records 100% of its deaths accurately.

• The Solution: Researchers use Microdata (surveys of small groups of families and households) to "approximate" what is happening in the rest of the world where official records don't exist.