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

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16 18 20 22 24 26 28 30 1

80

85

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105

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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

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45

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1 to

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10 to

19

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29

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49

50 to

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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

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+

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