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Heat-Related Mortality in
Washington State: Past and Future
The Washington Climate Change
Impacts Assessment Conference
February 12, 2009
J. Elizabeth Jackson
University of Washington
Heat: Core Public Health Concern

Heat waves linked with hundreds of
deaths in the United States annually



Chicago, 1995: estimated 700 deaths
Europe, 2003: estimated 30,000 deaths
UK, 2003: estimated 2,000 deaths
Heat: Core Public Health Concern

Heat waves linked with hundreds of
deaths in the United States annually

Heat waves projected to increase in
frequency, duration and intensity
Heat: Core Public Health Concern

Heat waves linked with hundreds of
deaths in the United States annually

Heat waves projected to increase in
frequency, duration and intensity

Heat-related mortality is likely underreported
Heat: Core Public Health Concern

Heat waves linked with hundreds of
deaths in the United States annually

Heat waves projected to increase in
frequency, duration and intensity

Heat-related mortality is likely underreported

What about Washington State?
Thermal Stress

Hyperthermia: the body cannot dissipate
heat absorbed from the environment (CDC,
2005)
Thermal Stress

Hyperthermia: the body cannot dissipate
heat absorbed from the environment (CDC,
2005)

Vulnerable Groups





Elderly
Urban residents
Those with chronic or mental illnesses
The poor, the socially isolated
Outdoor laborers
Other Vulnerabilities
Major cities of Washington State are
particularly at risk for high mortality during
heat waves

Milder summers = less adaptation to heat

Little residential air conditioning

Heat Island Effect
Analytic Goals

Establish historical relationship between
heat events and mortality (1980-2006)
Analytic Goals

Establish historical relationship between
heat events and mortality (1980-2006)

Estimate future mortality due to heat, i.e.,
“excess deaths” (2025, 2045, 2085)
Analytic Goals

Establish historical relationship between
heat events and mortality (1980-2006)

Estimate future mortality due to heat, i.e.,
“excess deaths” (2025, 2045, 2085)

Customize estimates for 4 study areas:




Greater Seattle Area (King, Pierce, Snohomish)
Spokane
Tri-cities (Benton, Franklin)
Yakima
Measuring Heat Events

Humidex: combined effects of heat and
humidity

Heat event threshold: hottest 1% of all
days (99th percentile humidex)

Heat Events: Counted the number of
heat events and the duration of each heat
event

Three climate change scenarios: high,
moderate and low summer warming
Measuring Mortality

Outcome: daily mortality rate, MaySeptember (= deaths/population)

Age groups: 45 and older; 65 and older;
85 and older

Causes of death


All non-traumatic causes
Circulatory, Cardiovascular, Respiratory (not
presented)
Method: Historical Relationship
Relative Risk of death during a heat event =
Mean Daily Mortality Rate(heat event)
Mean Daily Mortality Rate(non-event)
If RR > 1, then risk of death is greater
during heat events
Method: Future Excess Mortality
Excess deaths during future heat events are
calculated from:



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Baseline Mortality Rate
Risk of death during heat event
Future population
Climate change
Mean Daily Mortality Rate(non-event) *(Relative Risk – 1)*
Projected Population*Projected Heat Events
Baseline Population Parameters
4.0
Yakima
Tri-cities
Spokane
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
1980
2006
Greater Seattle Area
1980
2006
Eastern Washington
Baseline Climate Parameters
Heat Events, 1980-2006
Threshold, °F
Mean annual number
Mean duration
Greater
Seattle Area
Spokane
Tri-Cities
Yakima
92.5
1.7
2.2
100.6
1.8
2.0
100.9
1.6
2.2
95.9
1.6
2.3
Relative Risk (non-traumatic), Seattle
2.00
Aged 45+
Aged 65+
Aged 85+
Relative Risk
1.75
1.50
1.25
1.00
0.75
0
1
2
3
Heat event duration (days)
4
5
Relative Risk (non-traumatic), East
2.00
Aged 45+
Aged 65+
Aged 85+
Relative Risk
1.75
1.50
1.25
1.00
0.75
0
1
2
3
Heat event duration (days)
4
5
Projected Climate Parameters
12
10
8
Greater Seattle
Eastside
High
Moderate
6
4
Low
2
19
80
20
00
20
20
20
40
20
60
20
80
21
00
19
80
20
00
20
20
20
40
20
60
20
80
21
00
0
Number of Heat Events
Projected Climate Parameters
7
6
Greater Seattle
Eastside
High
5
4
3
2
Moderate
Low
1
19
80
20
00
20
20
20
40
20
60
20
80
21
00
19
80
20
00
20
20
20
40
20
60
20
80
21
00
0
Average Duration of Heat Events
Projected Excess Deaths, Seattle†
1000
750
85+
65-84
45-64
500
250
0
2025 2045 2085 2025 2045 2085 2025 2045 2085
Low
Moderate
† Population held constant at 2025 projection
High
Projected Excess Deaths, East†
100
75
85+
65-84
45-64
50
25
0
2025 2045 2085 2025 2045 2085 2025 2045 2085
Low
Moderate
† Population held constant at 2025 projection
High
Discussion

Why the difference between East and
West?
Discussion

Why the difference between East and
West?

Our estimates of excess deaths due to
future heat are conservative

Population growth not factored in

Analysis of past heat events may
underestimate effect of longer, hotter events
Discussion

Why the difference between East and
West?

Our estimates of excess deaths due to
heat are conservative


Population growth not factored in

Analysis of past heat events may
underestimate effect of longer, hotter events
Consider the possibility of higher-order
failures
Limitations

Use of county as geographic level linking
heat events and mortality
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Reliability of climate and population
projections

Change in cause-of-death coding during
historical study period

Method does not allow for analysis of
smaller, dispersed populations
Conclusions
 Heat
Stress is already a significant
factor in Washington mortality
 The
number of heat-related deaths
will increase because of climate
change
Acknowledgements
Co-Authors
Michael G. Yost PhD, UW Env & Occ Health Sciences
Catherine Karr MD PhD, UW Env & Occ Health Sciences, Pediatrics
Cole Fitzpatrick MA, UW Env & Occ Health Sciences
Brian K. Lamb PhD, WSU Lab for Atmos Research, Civil & Env Engineering
Serena H. Chung PhD, WSU Lab for Atmos Research, Civil & Env Engineering
Jack Chen PhD, National Research Council Canada, Ottawa, ON, Canada
Jeremy Avise PhD, California Air Resources Board, Sacramento, CA
Roger A. Rosenblatt MD, UW Family Medicine
Richard A. Fenske PhD, UW Env & Occ Health Sciences
CIG/JISAO
Phil Mote PhD
Eric Salathe PhD
Alan Hamlet PhD
Marketa McGuire Elser PhD
Lara Whitely Binder