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HOW HOT IS HOT?. Paul Wilkinson Public & Environmental Health Research Unit London School of Hygiene & Tropical Medicine Keppel Street London WC1E 7HT (UK). CLIMATE OR WEATHER?. 1 HEAT WAVES 2 TEMPERATURE-RELATED IMPACTS 3 ECOLOGICAL IMPACTS. HEAT WAVES & TEMPERATURE. - PowerPoint PPT Presentation
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HOW HOT IS HOT?
Paul WilkinsonPublic & Environmental Health Research Unit
London School of Hygiene & Tropical MedicineKeppel Street
London WC1E 7HT (UK)
CLIMATE OR WEATHER?
1 HEAT WAVES
2 TEMPERATURE-RELATED IMPACTS
3 ECOLOGICAL IMPACTS
HEAT WAVES & TEMPERATURE
• Episode analysis- transparent- risk defined by comparison to local baseline
• Regression analysis- uses all data- requires fuller data and analysis of
confounders- can be combined with episode analysis
No.
of
death
s/day
Date
Influenza ‘epidemic’
Period of heat
Smooth function of date with control for
influenza
Smooth function of date
Triangle: attributable deaths
PRINCIPLES OF EPISODE ANALYSIS
020
4060
80M
ean
daily
tem
per
atu
re (
degr
ees
Ce
lsiu
s)
010
020
030
0D
eat
hs
01jan2003 01apr2003 01jul2003 01oct2003 01jan2004Date
DEATHS, LONDON, 2003
1 A
ugu
st
16 A
ugus
t
020
4060
80M
ean
daily
tem
per
atu
re (
degr
ees
Ce
lsiu
s)
010
020
030
0D
eat
hs
01jan2003 01apr2003 01jul2003 01oct2003 01jan2004Date
DEATHS, LONDON, 2003
1 A
ugu
st
16 A
ugus
t
020
4060
80M
ean
daily
tem
per
atu
re (
degr
ees
Ce
lsiu
s)
010
020
030
0D
eat
hs
01jan2003 01apr2003 01jul2003 01oct2003 01jan2004Date
DEATHS, LONDON, 2003
1 A
ugu
st
16 A
ugus
t
020
4060
80M
ean
daily
tem
per
atu
re (
degr
ees
Ce
lsiu
s)
010
020
030
0D
eat
hs
01jan2003 01apr2003 01jul2003 01oct2003 01jan2004Date
DEATHS, LONDON, 2003
020
4060
80M
ean
daily
tem
per
atu
re (
degr
ees
Ce
lsiu
s)
010
020
030
0D
eat
hs
16jul2003 30jul2003 13aug2003 27aug2003Date
DEATHS, LONDON, 2003
MORTALITY IN PARIS, 1999-2002 v 2003
peak: 13 Aug
INTERPRETATION
• Common sense, transparent• Relevant to PH warning systems
But• How to define episode?
- relative or absolute threshold- duration- composite variables
• Uses only selected part of data• Most sophisticated analysis requires same
methods as time-series regression
020
4060
80M
ean
daily
tem
per
atu
re (
deg
ree
s C
elsi
us)
010
020
030
0D
eat
hs
01jan2001 01jan2002 01jan2003 01jan2004Date
DEATHS, LONDON, 2001-2003
100
150
200
250
300
De
aths
pe
r d
ay
0 10 20 30Mean temperature / Celsius
DEATHS, LONDON, 2001-2003
025
5075
100
125
150
Fre
quen
cy /
Pre
dict
ed
exc
ess
deat
hs a
da
y
010
020
030
040
050
060
0T
ota
l exc
ess
dea
ths
(ris
k x
freq
)
0 5 10 15 20 25 30Mean temperature / Celsius
TEMPERATURE-RELATED DEATHS, LONDON, 2001-2003
TIME-SERIES REGRESSION
• Short-term temporal associations
• Usually based on daily data (for heat) over several years
• Similar to any regression analysis but with specific features
• Methodologically sound as same population compared with itself day by day
• Time-varying confoundersinfluenzaday of the week, public holidayspollution
• Secular trend
• Season
STATISTICAL ISSUES 1
STATISTICAL ISSUES 1I
• Shape of exposure-response functionsmooth functionslinear splines
• Lagssimple lagsdistributed lags
• Temporal auto-correlation
Source: Anderson HR, et al. Air pollution and daily mortality in London: 1987-92. Br Med J 1996; 312:665-9
THE MODEL…
(log) rate = ß0 +
ß1(high temp.) +
ß2(low temp.)
ß1=heat slopeß2=cold slope
+
ß3(pollution) +
ß4(influenza) +
ß5(day, PH)
measured confounders+
ß6(season) +
ß7(trend)unmeasured confounders
LAGS
• Heat impacts short: 0-2 daysCold impacts long: 0-21 days
• Vary by cause-of-death- CVD: prompt- respiratory: slow
• Should include terms for all relevant lags
LONDON, 1986-96: LAGS FOR COLD-RELATED MORTALITY
% I
NC
RE
AS
E I
N M
OR
TA
LIT
Y/
ºC F
ALL
IN
TE
MP
ER
AT
UR
E
DAYS OF LAG
ALL CAUSE
0 5 10 151.65
1.7
1.75
1.8
1.85
CARDIOVASCULAR
0 5 10 151.7
1.75
1.8
1.85
1.9
RESPIRATORY
0 5 10 153.8
3.9
4
4.1
4.2
NON-CARDIORESPIRATORY
0 5 10 15.7
.8
.9
1
Lag
RR
0 5 10 15 20
1.0
00
1.0
05
1.0
10
*
**
** * * *
**
**
**
** * *
* *
*
*
*
* * **
**
**
**
** * * * * *
*
*
SANTIAGO: COLD-RELATED MORTALITYCARDIO-VASCULAR DISEASE
Lag
RR
0 5 10 15 20
0.9
95
1.0
00
1.0
05
1.0
10
1.0
15
*
* **
* * * * * * * * * * **
* * *
*
*
*
*
* * **
* * * * * * * * ** * *
* *
*
SANTIAGO: COLD-RELATED MORTALITYRESPIRATORY DISEASE
THRESHOLDS, SLOPES & LAGS
LJUBLJANA
-10 0 10 20 30 40
80100120140
BUCHAREST
-10 0 10 20 30 40
80100120140
SOFIA
-10 0 10 20 30 40
80100120140
DELHI
-10 0 10 20 30 40
80100120140
MONTERREY
-10 0 10 20 30 40
80100120140
MEXICO
-10 0 10 20 30 40
80100120140
CHIANGMAI
-10 0 10 20 30 40
80100120140
BANGKOK
-10 0 10 20 30 40
80100120140
SALVADOR
-10 0 10 20 30 40
80100120140
SAO PAULO
-10 0 10 20 30 40
80100120140
SANTIAGO
-10 0 10 20 30 40
80100120140
CAPE TOWN
-10 0 10 20 30 40
80100120140
LAG: 0-1 DAYSHEAT
LJUBLJANA
-10 0 10 20 30 40
80100120140
BUCHAREST
-10 0 10 20 30 40
80100120140
SOFIA
-10 0 10 20 30 40
80100120140
DELHI
-10 0 10 20 30 40
80100120140
MONTERREY
-10 0 10 20 30 40
80100120140
MEXICO
-10 0 10 20 30 40
80100120140
CHIANGMAI
-10 0 10 20 30 40
80100120140
BANGKOK
-10 0 10 20 30 40
80100120140
SALVADOR
-10 0 10 20 30 40
80100120140
SAO PAULO
-10 0 10 20 30 40
80100120140
SANTIAGO
-10 0 10 20 30 40
80100120140
CAPE TOWN
-10 0 10 20 30 40
80100120140
LAG: 0-13 DAYSCOLD
Threshold for heat effect
Threshold for cold effect
Cutpoint
302520151050-5-10-15
40
30
20
10
0
-10
Pop attrib frac
% change
Threshold
Variation in ‘heat slope’ & attributable deaths with threshold
SOFIA, 0-1 DAY LAG
CONTROLLNG FOR SEASON
TEMPERATURE
MORTALITYSEASON
Infectious disease
Diet
UNRECORDED FACTORS
Human behaviours
X ?
• Moving averages
• Fourier series (trigonometric terms)
• Smoothing splines
• Stratification by date
• Other…
METHODS OF SEASONAL CONTROL
• Provide evidence on short-term associations of weather and health
• ‘Robust’ design
• Repeated finding of direct h + c effects
• Some uncertainties over PH significance
• Uncertainties in extrapolation to future(No historical analogue of climate change)
SUMMARY: TIME-SERIES STUDIES
HOW HOT IS HOT?
Depends on…
• Climate!(Threshold tends to be higher in warmer climates > acclimatization or adaptation)
• Characteristics of heat (esp. duration)
• Characteristics of the population
But
• Heat effect identified in (almost) all populations studied to date
• Some evidence for steep increases in risk at extreme high temperatures
Health impact model Generates comparative estimates of the regional impact of each climate scenario on specific health outcomes
Conversion to GBD ‘currency’ to allow summation of the effects of different health impacts
GHG emissions scenarios Defined by IPCC
GCM model: Generates series of maps of predicted future distribution of climate variables
Level Age group (years)0-4 5-14 15-29 30-44 45-59 60-69 70+
1 1.0 1.0 1.0 1.0 1.0 1.0 1.02 1.2 1.2 1.2 1.2 1.2 1.2 1.23 1.7 1.7 1.7 1.7 1.7 1.7 1.71 1.0 1.0 1.0 1.0 1.0 1.0 1.02 1.2 1.2 1.2 1.2 1.2 1.2 1.23 1.7 1.7 1.7 1.7 1.7 1.7 1.71 1.0 1.0 1.0 1.0 1.0 1.0 1.02 1.2 1.2 1.2 1.2 1.2 1.2 1.23 1.7 1.7 1.7 1.7 1.7 1.7 1.71 1.0 1.0 1.0 1.0 1.0 1.0 1.02 1.2 1.2 1.2 1.2 1.2 1.2 1.23 1.7 1.7 1.7 1.7 1.7 1.7 1.71 1.0 1.0 1.0 1.0 1.0 1.0 1.02 1.2 1.2 1.2 1.2 1.2 1.2 1.23 1.7 1.7 1.7 1.7 1.7 1.7 1.7
ASSESSMENT OF FUTURE HEALTH IMPACTS
0 10 20 30 40
80
100
120
140
Heat-related mortality, DelhiR
ela
tive m
ort
alit
y (
% o
f d
aily
avera
ge)
Daily mean temperature /degrees Celsius
Temperature distribution
• EXTRAPOLATION(going beyond the data)
• VARIATION(..in weather-health relationship -- largely unquantified)
• ADAPTATION(we learn to live with a warmer world)
• MODIFICATION(more things will change than just the climate)
• ANNUALIZATION(is the climate impact the sum of weather impacts)
BUT FIVE REASONS TO HESITATE…
VECTOR-BORNE DISEASE
050
100
150
Dea
ths
per
100,
000
Sub-Saharan Africa
North & West Africa
Asia/Pacific
Latin America
Developed countries
Malaria mortality rates by region
050
100
150
Dea
ths
per
100,
000
Sub-Saharan Africa
North & West Africa
Asia/Pacific
Latin America
Developed countries
Malaria mortality rates by region
Source: WHO
TRANSMISSION POTENTIAL
0
0.2
0.4
0.6
0.8
1
14 17 20 23 26 29 32 35 38 41
Temperature (°C)
Incubation period
0
10
20
30
40
50
15 20 25 30 35 40
(day
s)
Temp (°C)
Survival probability
0
0.2
0.4
0.6
0.8
1
10 15 20 25 30 35 40
(per
day
)Temp (°C)
ParasiteBiting frequency
0
0.1
0.2
0.3
10 15 20 25 30 35 40
(per
day
)
Temp (°C)
Mosquito
• NON-CLIMATE INFLUENCES
• OTHER CLIMATIC FACTORS
• TREATMENTS / ERADICATION PROGRAMMES
SO, TEMPERATURE IMPORTANT BUT…
CONTACT DETAILS
Sari KovatsPaul Wilkinson
Public & Environmental Health Research UnitLondon School of Hygiene & Tropical MedicineKeppel StreetLondonWC1E 7HT(UK)
www.lshtm.ac.ukTel: +44 (0)20 7972 2415Fax: +44 (0)20 7580 4524
[email protected]@lshtm.ac.uk