Transcript What's the single best method of prevention or cure ever devised to improve public or personal health? CHRISTOPHER DYE Hygeia and Panacea: is prevention better than cure?

What's the single best
method of prevention or
cure ever devised to
improve public or
personal health?
CHRISTOPHER DYE
Hygeia and Panacea:
is prevention better than cure?
Prevention is better than cure
Dangerous myth…
“Dad always
thought
laughter was
the best
medicine, which
I guess is why
several of us
died of
tuberculosis.”
Prevention is better than cure
…or universal truth?
Scurvy, "limeys" and vitamin C
James Lind 1716-94
A Treatise of the Scurvy
Treatise on Preparation
for Death
On Civility in Children
Adagia
"Prevention is
better than cure"
Desiderius
Erasmus
1466-1536
1. When prevention
is better than cure
Deaths per million population
Where 60 million people die
double burden of disease in low-income countries
8
6
Low-middle income
High income
4
2
0
Communicable,
pregnancy,
nutrition
Noncommunicable
Injuries
Currency of illness and death
WHAT'S THE HUMAN
COST OF RABIES…
…AS COMPARED WITH
HEART DISEASE?
Currency of illness and death
HOW TO COMPARE RABIES WITH
HEART DISEASE?
DISABILITY-ADJUSTED LIFE YEAR
(DALY)
DALY = YEARS LOST TO ILLNESS
× DISABILITY WEIGHT
+ YEARS LOST BY DEATH
U
Pr pp
im er
ar
r
y esp
sy
ph
A ilis
st
hm
M
a
L i ea
ve sl
r c es
an
ce
r
Lo
w TB
e
H rr
ea es
rt
p
at
ta
ck
A
ID
Te Me
rm nin S
in ig
al iti
ca s
nc
er
D
ea
th
perfect health......death
Disability weights for selected conditions
1
0.8
0.6
0.4
0.2
0
An ounce of prevention or
a pound of cure?
Cost/yr healthy life ($/DALY)
TOBACCO: 5 MILLION DEATHS ANNUALLY
1000000
100000
10000
1000
100
Tobacco
price
increase
Nicotine
replacement
Promoting
cessation
etc
Treatment
lung, liver,
stomach
cancer
Tobacco tax works!
8
14
7
12
6
10
5
8
4
1980
1985
1990
1995
2000
6
2005
Millions sold
$ price 20 cigarettes
Cigarette sales New Zealand
DALYs: all we need to know?
Prevention or treatment of terminal cancer?
Choose:
(a) Palliative treatment to extend days of
healthy life in people with cancer
Or:
(b) Preventive measures (advertising,
taxation etc) to reduce cancer incidence
Assume cost per DALY is the same
Climate & health:
An inconvenient truth?
"The benefits of strong, early action on
climate change outweigh the costs"
STERN REVIEW November 2006: The
Economics of Climate Change
Michael Mann's "hockey stick"
Global warming: damage to health
Rise ºC
Some health consequences
1
300,000 people die each year from climaterelated diseases - diarrhea, malaria, malnutrition
2
40 – 60 million more people exposed to malaria
in Africa
3
1 – 3 million more people die from malnutrition (if
carbon fertilization weak)
4
Up to 80 million more people exposed to malaria
in Africa
5+
Major disruption and large-scale movement of
population
Easier and harder ways to keep CO2
at or below 550 parts per million
Global emissions (GtCO2)
70
Delayed action
60
Prompt action
50
Stabilization beyond
reach?
40
30
Stabilization feasible
20
10
0
2000
2020
2040
2060
2080
2100
"The cost of investment would be
trivial by comparison with the
possible damage"
Investment
1% per year of global GDP over next 50
years
Damage
2-3 ºC : 0-3% GDP in late 21st century
5-6 ºC : 5-20% GDP ($4 trillion per year)
Bond… Market Bond
Financing sanitation and vaccines
Human
Development
Report 2006
“the rates of return from upfront
investment in water and sanitation would
significantly outweigh the costs of
borrowing from bond markets…”
Smallpox: what value eradication?
Day 3
Synchronous
eruption of
lesions
Day 5
Rash turns to
vesicles and
pustules
Day 7
Large lesions
with central well
Case fatality
30%
From inoculation to vaccination
to eradication
DA Henderson
WHO Eradication
campaign
(1966-1977)
Lady Mary Wortley
Montague
(1689-1762)
Edward Jenner
(1749-1823)
Smallpox inoculation: tools of the trade
"Just eradicate the disease, and
let the skeptics talk to each
other" UNICEF
Cost of
eradication
in
external
funding
$125
million
1967
About 10,000
cases per
month
1977
Last case 26
October 1977
Poliomyelitis:
prevention far better than cure
Polio vaccines
Sabin & Salk
Polio eradication?
>1600 cases in 2006
India
Pakistan
Afghanistan
Nigeria
Total external spending ~ $4 bn
Initial estimate $300 million
2. When cure is the
only option
Leprosy: curable but not preventable
3. When cure is
also prevention
Cost/yr healthy life gained ($/DALY)
TUBERCULOSIS: 1.7 MILLION
DEATHS ANNUALLY
100000
10000
Cure
Prevention
1000
100
10
1
Treat latent
Treat
BCG
Treat active
infection resistant TB vaccination
TB
4. When cure is the
sister of prevention
Hygeia and Panacea
cleanliness (and healing) are next to
godliness
Asklepios - medicine and healing
Hygeia - cleanliness
Panacea - healing
Cost/year healthy life ($/DALY)
MALARIA:1.2 MILLION DEATHS ANNUALLY
Combine prevention and cure
low- and middle-income countries: up to
80
4 methods of prevention
1 method of cure
60
40
20
0
Bednets with
insecticide
House
spraying
insecticide
Prophylactic Prophylactic
Drug
drugs for
drugs in
treatment
children
pregnancy children with
malaria
Cost/year healthy life ($/DALY)
DIARRHEA: 1.8 MILLION DEATHS/YEAR
methods for prevention and cure
5000
Cure
4000
3000
2000
1000
0
Prevention
The 60 countries with the highest numbers
or rates worldwide of child mortality
Child deaths: task is not to choose prevention
or cure, but to implement all feasible solutions
target -4.3%
Sub-Saharan Africa
South Asia
Middle East
Latin America
Europe & Central Asia
East Asia
Faster economic
growth
Fall 1990-2000
-5
-4
-3
-2
-1
Annual fall in child mortality (U5M %)
0
Effective prevention and cure
Prevention
Cure
Child deaths
Breastfeeding
handwashing
Oral rehydration
Antibiotics
Maternal deaths
Family planning
Micronutrients
Obstetrics
Antibiotics
Nutrition
Breastfeeding
Hygiene/sanitation
Macro- and
micronutrients
HIV/AIDS
Safe sex
Treat STI
Antibiotics
Antiretrovirals
Tuberculosis
Treat active TB
BCG
Treat active TB
Treat TB/HIV
Malaria
Bednets
House spraying
Case management
5. How individuals
approach
prevention and
cure
Why take the risk?
Are you "risk averse" or "risk prone"?
 Plain ignorance (AIDS is not curable)
 It'll never happen to me (delusional)
 The future may never come
(discounting)
 Peer pressure (Kool and the Gang)
 For kicks (excitement, bore/freedom)
 Refusal to pay for insurance
Risk, roulette and health insurance
Type of Gamble
Expected average value
relative to amount bet
Roulette
You lose 5% of each bet
Large group health
insurance
Individual health
insurance
You lose 10% of each bet
You lose 40% of each bet,
the price of "peace of
mind"
see www.gresham.ac.uk
6. Magic bullets &
Nobel Prizes
Cure is cleverer than prevention?
186 Nobel Prizes for Medicine, 1901-2006
Basic science
Cure/therapy
Prevention
172
12
2
Theiler 1905
Ehrlich 1908 +
Mechnikov 1908
Paul Ehrlich's
(1854-1915)
"magic bullets"
Prevention: "side-chain"
theory of immunity based
on antibody
Cure: drugs selectively
targeting pathogens -arsenic-based Salvarsan
to treat syphilis
Smoking one of his
"25 strong cigars a
day"
Died of stroke
Magic bullets, besides penicillin…
Fleming
Chain
Florey
1928/41
Aspirin (acetylsalicylic acid, 1899)
 Analgesic against minor pains and aches
 Antipyretic against fever
 Anti-inflammatory against arthritis
 Anti-platelet blood-thinner
 Anti-stick stops bacteria growing on
contact lenses
 Side effects gastrointestinal distress
(ulcers, stomach bleeding), tinnitus,
bleeding in menstruation
Sir John Vane, Nobel Prize 1982
Aspirin reduces strokes in women (17%)
and heart attacks in men (32%)
women have slightly more strokes than heart attacks, men tend to have more
heart attacks than strokes (JAMA vol 295, p 306, 2005)
Praziquantel vs schistosome flukes
250 million people infected with schistosomes
Adult flukes killed with a single dose of PZQ
Is prevention better than cure?
In formal analysis, not necessarily…
• Aetiology of some diseases unknown
some conditions unpreventable
• Prevention vs cure is not always the right
question
both are needed and feasible e.g. child
mortality in LDCs
• We value more than is captured in formal
analysis
which gives guidance, not rules
PREVENTION VS CURE: A STRAW POLL AT WHO
Votes for prevention
0
1
2
3
Votes for cure
0
4
Vaccination
Antibiotics
Clean water
Surgery
Handwashing
Good
doctors
Nutrition
ORT
diarrhea
The pill
Seatbelts
Sterilization
Covered
cough
Vitamins
1
2
3
4
5