Thomas J. Kim, MD, MPH Roger B. Trent, Ph.D. California Department of Public Health
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Transcript of Thomas J. Kim, MD, MPH Roger B. Trent, Ph.D. California Department of Public Health
Heat-Related Deaths Associated with a Severe Heat Wave — California, July 2006
California Public Health Association—North
March 2008
Thomas J. Kim, MD, MPHRoger B. Trent, Ph.D.
California Department of Public HealthClimate Change Public Health Impacts Assessment and
Response Collaboration
Heat Waves as Environmental Disasters
July 20, 2006
July 2006 California Heat Wave
• July 15 – August 1 • ≥3 days of ≥100° F shade temperature• ≥2 days of ≥105° F heat index• Record breaking maximum temperatures• High minimum temperatures • Long duration
Heat-Related Illness is a Continuum
• Heat stress and exhaustion– Cramping– Heavy perspiration– Weakness
• Heat Stroke– Core body temperature >104°F– Multi-organ system dysfunction– Often fatal despite treatment
Risk Factors in Heat-Related Deaths
• Exertion• Dehydration• Infant or Age >60• Lack of air conditioning • Social isolation• Chronic diseases (CVD, COPD)• Cognitive and mobility impairments• Low socio-economic status• Housing characteristics
Objectives of Study
• Describe heat-related deaths in California
• Provide data on risks to help plan response
• Not an “excess mortality” study to statistically estimate the effect of the heat wave on death rates
Methods
• Case series• Coroner reports
– Investigative narrative– Toxicology
• Abstraction form• Denominator data from 2005 US Census
estimates• Compared to California mortality data
Case Definition
• Death of a state resident of any age• Death between July 15 – August 1• Underlying or contributory cause of death• No evidence of trauma and at least one of the
following:– Core body temperature ≥ 105°F (≥ 40°C)– Decomposed body, person last seen alive at
onset of heat wave– High environmental temperature at death scene
0
5
10
15
20
25
30
16 18 20 22 24 26 28 30 1
80
85
90
95
100
105
110
Tem
per
atu
re (
F)
Heat-Related Death in California, July 15 – August 1, 2006 (n=140)
Nu
mb
er
of
Ca
ses
Date of Death in July 2006
Northern Central Valley (Willows)
Heat-Related Deaths in Counties with ≥10 Deaths, July 15 – August 1
No. (%) Rate/100,000 population
(95% CI)
Imperial 10 (7) 6.4 (2.4 – 10.4)
Stanislaus 23 (16) 4.6 (3.0 – 6.4)
San Joaquin 21 (15) 3.2 (1.8 – 4.5)
Fresno 20 (14) 2.3 (1.2 – 3.2)
Kern 15 (11) 2.0 (1.0– 2.9)
Sacramento 13 (9) 0.9 (0.4 – 1.5)
California: June – Aug (1999-2004)
0.12 / 100,000 population
High Temperatures, Heat Deaths, July 2006
Demographics of Heat-Related Deaths (n=140)
Characteristic
Case (%)
% CAMortality OR (95% CI)
Male 66 50 2.0 (1.3–2.8)
White, Non-Hispanic 63 71 referent
Hispanic 24 14 1.9 (1.2–2.9)
Black, Non-Hispanic 12 8 1.8 (1.0–23.2)
Asian / Pacific Islander 1 7 0.1 (0.01–0.8)
Unknown race 19
0
5
10
15
20
25
30
35
40
45
0-1
1 to
9
10 to
19
20 to
29
30 to
39
40 to
49
50 to
59
60 to
69
70 to
79
80+
Heat Deaths
2003 CA All-CauseMortality
Distribution of Heat-Related Deaths by Age(Range: 10–98)
Pe
rce
nt
Age
Age Distribution of Heat-Related Deaths by Hispanic Ethnicity
05
10152025303540
1-9
10-1
9
20-2
9
30-3
9
40-4
9
50-5
9
60-6
9
70-7
980
+
Age
Pe
rce
nt
Hispanic (n=23)
Non-Hispanic (n=90)
Air Conditioning (AC) Use Among Indoor Decedents (n=96)
Status No. (%)
AC not present 42 (45)
AC Unknown 19 (20)
AC present 35 (35)
Not functional 16 (46)
Functional 19 (54)
Used 1 (5)
Not used 18 (95)
Air Conditioning (AC) Use Among Indoor Decedents (n=96)
Status No. (%)
AC not present 42 (45)
AC Unknown 19 (20)
AC present 35 (35)
Not functional 16 (46)
Functional 19 (54)
Used 1 (5)
Not used 18 (95)
Recent Social Contact Before Death of Decedents Who Lived Alone
140 Total decedents
65 Lived alone
34 Lived with others41 Unknown
19 (29%) seen ≤ 24 hours
17 Seen > 24 hrs
36 (55%) with known recent social contact
29 without known recent social contact
Chronic Disease Conditions Among Heat-Related Deaths
Disease %
Cardiovascular 47
23
17
7
2
Psychiatric
Alcohol abuse / dependence
Pulmonary
Confined to bed
Limitations
• Lack of information on decedents– Knowledge of alerts and risk reduction steps– Presenting symptoms
• Coroner reports– Not designed specifically for public health use– Data on deaths, not on heat morbidity
Discussion
• 71% had one or more commonly known risk factors
• Non-use of functioning air conditioners in 13%
• Possible ineffective assessment and intervention by social contact prior to death
• Younger age in Hispanic decedents
Recommendations
• Clearly define threshold for intervention by social contacts – Not to wait for symptoms– Based on forecast and risk factors
• Concentrate on populations and areas of special risk
• Conduct active surveillance or case control study in heat illness– AC use– Tailor prevention messages for high risk groups
Did we count them all?
Heat Exhaustion Heat Stroke
Physician
diagnosis
Coroner determination
Heat stroke is much easier to document than is heat that exacerbates existing conditions and causes higher death rates in general.
Two approaches to epidemiology of heat deaths
Coroner death case series • They investigate possible
homicides, suicides, accidents (including heat) and unexpected deaths to persons not seen by a physician in past 20 days.
• Based on investigation of death circumstances
• Evidence of heat stroke• Method: precise counts
of specific persons
Excess mortality study• “Heat stress”• “Harvesting effect”• “Forward displacement
of deaths”• “Statistical excess or
spike”• Method: compare
number of deaths on hot days to some baseline of days with “normal” weather
High Priority Studies for Heat Emergencies
• Death case series: done• Excess mortality estimate: planned (when all
death data for 2006 are available)• Studies of risks and protective factors for
nonfatal morbidity– To help public avoid illness and protect
health– To avoid straining ERs and EMS
Acknowledgments
California Department of Public Health
• Gayle Windham, PhD• Barbara Materna, PhD• Paul English, PhD• Helene Margolis, PhD• Dan Smith, Dr.PH• Kathleen Fitzsimmons,
MPH
Lawrence Berkeley National Lab
• Tom McKone, PhD
Centers for Disease Control and Prevention
• Janet Blair, PhD, MPH• Randolph Daley, DVM, MPH• George Luber, PhD• Bruce Gutelius, MD• Tom Weiser, MD