Mapping community determinants of heat vulnerability.
BACKGROUND
The evidence that heat waves can result in both increased deaths and illness is substantial, and concern over this issue is rising because of climate change. Adverse health impacts from heat waves can be avoided, and epidemiologic studies have identified specific population and community characteristics that mark vulnerability to heat waves.


OBJECTIVE
We situated vulnerability to heat in geographic space and identified potential areas for intervention and further research.


METHODS
We mapped and analyzed 10 vulnerability factors for heat-related morbidity/mortality in the United States: six demographic characteristics and two household air conditioning variables from the U.S. Census Bureau, vegetation cover from satellite images, and diabetes prevalence from a national survey. We performed a factor analysis of these 10 variables and assigned values of increasing vulnerability for the four resulting factors to each of 39,794 census tracts. We added the four factor scores to obtain a cumulative heat vulnerability index value.


RESULTS
Four factors explained > 75% of the total variance in the original 10 vulnerability variables: a) social/environmental vulnerability (combined education/poverty/race/green space), b) social isolation, c) air conditioning prevalence, and d) proportion elderly/diabetes. We found substantial spatial variability of heat vulnerability nationally, with generally higher vulnerability in the Northeast and Pacific Coast and the lowest in the Southeast. In urban areas, inner cities showed the highest vulnerability to heat.


CONCLUSIONS
These methods provide a template for making local and regional heat vulnerability maps. After validation using health outcome data, interventions can be targeted at the most vulnerable populations.
Reid
Colleen E
CE
Environmental Health Sciences Division, School of Public Health, University of California at Berkeley, California 94720-7360, USA. creid@berkeley.edu
O'Neill
Marie S
MS
Gronlund
Carina J
CJ
Brines
Shannon J
SJ
Brown
Daniel G
DG
Diez-Roux
Ana V
AV
Schwartz
Joel
J
D000368:Aged; D000389:Air Conditioning; D003920:Diabetes Mellitus / Q000453:epidemiology; D055874:Extreme Heat / Q000009:adverse effects*; D005163:Factor Analysis, Statistical; D040362:Geographic Information Systems; D018882:Heat Stress Disorders / Q000453:epidemiology* / Q000401:mortality; D006801:Humans; D015995:Prevalence; D012307:Risk Factors; D012934:Social Isolation; D012959:Socioeconomic Factors; D014481:United States / Q000453:epidemiology; D035862:Vulnerable Populations / Q000706:statistics & numerical data*