Week 2 Flashcards
Upstream forces
- much of environmental health is determined by upstream forces that seem at first glance to have little to do with environment or health
- upstream is the causes of the causes
Disability-adjusted life year or DALY
How many people die of BLANK, at what age do they die, and how long are they disabled by BLANK and how severe is that disability?
Key limitation: only tells us about death and disability from BLANK but tells us nothing about the causes of BLANK (the causes of the causes)
DALY = YLL + YLD = one lost year of healthy life
YLL - years of life lost
are years lost due to premature death
- calculated by subtracting the age at death from the longest possible life expectancy for a person at that age.
YLD - years lived with disability
can also be described as years lived in less than ideal health
- measured by: prevalence of the condition X (times) by the disability weight for that condition
- disability weights reflect the severity of different conditions and are developed through surveys of the general public
The Global Burden of Disease (GBD)
provides a tool to quantify health loss from hundreds of diseases, injuries, and risk factors, so that health systems can be improved and disparities can be eliminated
- useful source of information on both upstream contributors (risk factors) and downstream contributors (causes) to death and disease
To estimate the number of deaths or DALYs attributable to a risk factor, we need 4 types of info:
- exposure: how many people are exposed? how much are they exposed to?
- exposure-response relationship: how does health risk change as exposure changes?
- counterfactual: what is the alternative scenario
- burden estimate for the outcome: how many total deaths or DALYs are caused by the disease?
The prevention paradox
The prevention paradox is a situation where a population-based measure that benefits the community as a whole, has little to no impact on the individual-based level.
- a large number of people at a small risk may give rise to more cases of disease than the small number who are at a risk (Rose, 1985)
Air pollution stats
- second leading risk factor for early death worldwide
- 8.1 million deaths per year
- more than 700,000 deaths in children under 5 were from diseases linked ti air pollution in 2021, and 500,000 deaths from that were linked to exposure to household air pollution
- exposure to air pollution is linked to 1 in 8 deaths worldwide
- in 2021, air pollution was the leading contributor to total DALYs
Air pollution is responsible for: - 30% of deaths from lower respiratory infections
- 28% of deaths from ischemic heart disease
- 48% of deaths from chronic obstructive pulmonary disease
Hand hygiene stats
- 2.3 billion people lack a facility with water and soap available to wash their hands at home
- 670 million have no handwashing facility at all
- 460 million children attend schools with no hygiene facilities
GBD flaws
- Missing Exposure-Outcome Pairs – Many health risks (e.g., microplastics, new chemicals) are not yet included due to limited data or unclear causal links.
- Uncertainty in Exposure & Response Relationships – Measuring exposures (e.g., pollution, diet) is challenging, and the link between exposure levels and health outcomes can be uncertain.
- Health as a Continuum – Diseases exist on a spectrum, but GBD requires clear categories, which can create arbitrary cutoffs (e.g., when does high blood pressure become “hypertension”?).
- Disability Weights Subjectivity – Disability weights depend on surveys and expert opinions, which may not reflect cultural differences or individual experiences.
What is population health?
population health is a strategy or approach to health that aims to improve the health of the entire population and reduce health inequities among population groups
Clinical strategy
physicians diagnose people with signs or symptoms of a disease, preferably early in its course, and prescribe a drug or perform a surgical procedure
population strategy
scientists attempt to identify and reduce upstream risk factors in populations that cause disease
Sir George Pickering
- A British physician known for his work on hypertension.
- Argued that blood pressure is a continuum, not a strict disease category.
- Stated that higher blood pressure increases mortality risk, with no clear dividing line between “normal” and “hypertensive.”
- Criticized medicine’s reliance on binary thinking, emphasizing that essential hypertension is quantitative, not qualitative.
Dr. Jerry Morris & his population approach
The man who invented exercise
Population approach:
The stakes are high: small shifts in the population distribution of blood pressure or blood cholesterol could confer substantial benefit on community health, diminish suffering and lighten the burden on services out of all proportion
Rose’s Radical Ideas
- little shifts matter
- a large number of people at a small risk give rise to more cases of disease than the small number who are at a high risk
- there is no known biological reason why every population should not be as healthy as they can
Triggers of heart attacks - cocaine & air pollution
- cocaine puts a small number of people at a high risk of having a heart attack
- air pollution puts a large number of people at a small risk of having a heart attack
The iceberg
These environmental disaster only represent the tip of the iceberg. The impact of environmental toxins are insidious.
The vast majority of children whose brains are affected by toxins have subtle deficits or disorders that are not seen until years after the exposure began.
Prevention paradox looked through a different lens
Greater societal gain will be obtained by achieving a small reduction in alcohol misuse in a far larger group of “risky” drinkers with less serious problems than by trying to reduce problems among a smaller number of dependent drinkers
- to protect the few, protect the many
Dr. Ancel Keys
- PhD research: Studied how fish weight affected length.
- Big idea: Health trends come from community-wide factors, not just individuals.
- Created K-rations for soldiers (included cigarettes!).
- Promoted the Mediterranean diet, linking it to heart health.
Diseases common and rare
for a disease that is common in one place will usually prove to be rare somewhere else
Risk factors for CHD (canary heart disease)
- sex
- obesity
- smoking
- diabetes
- salt intake
- physical activity
- genetic susceptibility
- toxic metals
- air particles (PM 2.5)
Which of these risk factors changed? Not sex or genetics. Obesity and diabetes were increasing, not decreasing. Need salt intake and physical activity trends.
Toxic metals and mortality
Arsenic, lead, cadmium lead to CVD, CHD, and stroke.
Lead and CVD
lead enhances atherosclerosis in laboratory studies by inactivating NO, inhibiting endothelial repair, impairing angiogenesis and promoting thrombosis
- lead damages endothelial cells leading to increased likelihood of CVD
Lead and Coronary Heart Disease
People with higher amounts of lead in their blood were 2x more likely to die from coronary heart disease than people with lower amounts.
How much lead is safe for adults?
- No safe level – Even the lowest lead levels increase heart disease risk.
- 50 parts per billion is the federal action level, but harm occurs below this.
- Risk rises sharply with any lead exposure.
GBD for lead
annual deaths: 5.5 million
attributable fraction: 30% of CHD
Annual cost: US$ 4.6 trillion
GDP: 5.3% global GDP, 7.8% LMIC GDP
Rose prediction for blood pressure and hypertension
Predicted that small reductions in the mean blood pressure of populations result in large reductions in hypertension
Result:
From 1976 to 1994, systolic blood pressure dropped by 5 points in American men, from 130 to 125 mmHg, and by 6 points in American women, from 126 to 120 mmHg. Hypertension in American adults declined by 40%
men and women - lead and heart disease
More likely in men because the lead stays in the bones and blood (I think) and women flush it out because of menstruation but men flush it out too in a different way idk what I didn’t hear that one HAH
Dr. Yandell Henderson
Found that the use of tetraethyl lead will cause vast numbers of the population to suffer from slow lead poisoning with hardening of the arteries
Smoking ban
20% reduction in heart attacks
Precautionary principle
The precautionary principle states that if an action or substance poses a potential risk to human health or the environment, precautionary measures should be taken even if full scientific certainty is not yet available.
- It prioritizes prevention over waiting for definitive proof of harm.
Burden of proof
- The burden of proof is the responsibility to provide evidence for a claim
- When strong epidemiological evidence suggests a common exposure may cause harm, the burden of proof should shift.
- Instead of requiring proof of harm, those denying a causal link must prove it’s not harmful.
Conclusions
- clinical strategies and population strategies are complementary
- we are failing to prevent preventable diseases because too much emphasis on clinical strategies
- we should rely on the precautionary principle for widespread exposure to toxic chemicals and pollutants with no safe level
upstream vs downstream
Upstream Approaches focus on preventing health issues by addressing root causes (e.g., improving education and reducing poverty).
Downstream Approaches treat health problems after they occur (e.g., providing medical care for diabetes or heart disease).
