Assessing Vulnerability to Extreme Heat Among Residents of Urban Slums in Ahmedabad, India Público

Tran, Kathy Van (2012)

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India is expected to face increasingly frequent extreme weather events as a consequence
of climate change. Extreme heat events may have particularly significant impact since summer
temperatures are historically high. Little is known regarding factors that may drive population
vulnerability to extreme heat as well as strategies for minimizing heat exposure and susceptibility
in this rapidly developing nation. To facilitate public health preparedness for extreme heat, an
assessment of factors affecting vulnerability was conducted in summer of 2011 in Ahmedabad,
Gujarat, India, a city where seasonal highs have reached 46.8°C. The study focused on factors
that affect heat exposure, susceptibility to heat related illness, and adaptive capacity, all of which
feed into vulnerability to heat. Indicators of these factors were identified through literature review
and expert opinion and assessed through a cross-sectional household survey. The survey used
randomized multistage cluster sampling to identify target households in thirteen urban slum
populations in Ahmedabad. This population was presumed by local public health authorities to be
particularly vulnerable and have greater susceptibility and less resilience to extreme heat
exposure. Associations between heat-related morbidity and individual and household
demographics, medical history, access to weather warnings and health information, and social
connectedness were determined. Findings were summarized through descriptive statistics of
demographics, exposure, susceptibility, adaptive behaviors and outcomes. Multivariate logistic
regression was performed with Generalized Estimating Equations using an exchangeable
covariance matrix to account for clustering effects at the household and slum levels to test the
various associations between outcomes and covariates. Results indicated that age, income,
preexisting conditions, work location, drinking water sources, access to doctors and information,
and social connectedness influence the occurrence of heat-related symptoms and illnesses among
slum dwellers. These findings suggest several potentially worthwhile interventions targeting slum
dwellers including: working with community health workers and physicians to disseminate
information and prevent heat illnesses as well as delivering important health and heat information
through television campaigns. Future research studies might include conducting other heat
vulnerability studies with improvements to the survey used here, conducting focus groups, and
evaluating the effectiveness of currently applied adaptive behaviors and future interventions.

Table of Contents

Table of Contents

1. Background...1
1.1. Vulnerability...1-2
1.2. Historical Hazard Distribution - India's Climate...2
1.2.1. Recent Climate Shifts...2-3
1.2.2. Recent Shifts in Extreme Heat Events...3-4
1.3. Exposure to the Hazard of Extreme Heat...4-5
1.4. Suceptibility to Extreme Heat...5-7
1.5. Capacity to Adapt to Extreme Heat...7-8
1.6. Exploring Vulnerability to Extreme Heat in Context...8-9
2. Methods...9-10
2.1. Study Goal and Objectives...10-11
2.2. Study Setting...11-13
2.3. Sampling Strategy...13-14
2.4. Data Collection Methods...15
2.5. Data Management...15-16
2.6. Outcomes and Independent Variables...16
2.6.1. Primary Outcomes...17
2.6.2. Independent Variable Combinations and Recoding...17-18
2.7. Statistical Analysis...18
2.7.1. Management of Possible Clustering Effects...19
2.7.2. Multivariate Modeling...19-21
3. Results...21
3.1. Characteristics of Sampled Slums...21-22
3.2. Descriptive Analysis...22

3.2.1. Demographic Profile of the Sample...22-23
3.2.2. Heat-related Outcomes...23-24
3.2.3. Model Considerations for Demographics...24
3.2.4. Exposure Factors within Study Population...24-26
3.2.5. Susceptibility Factors within Study Population...26-28
3.2.6. Adaptive Behaviors within the Study Population...28-31
3.3. Regression Analysis and Hypothesis Testing...31
3.3.1. Age, Preexisting Conditions, Occupational Exposure, and Associations with Heat Illness...31-32
3.3.2. Access to Heat-Related Information and Heat Illness...32
3.3.3. Social Connectedness and Heat Illness...33
3.3.4. Additional Risk and Protective Factors...33-34
4. Discussion...34
4.1. Differences Among the Zones...34-35
4.2. Associations Between Outcomes and Covariates...35-37
4.3. Limitations...37
4.3.1. Potential Threats to Internal Validity - Cross-Sectional Design...37-38
4.3.2. Potential Threats to Internal Validity - Interviewer Bias...38-39
4.3.3. Potential Threats to Internal Validity - Survey Development...39-40
4.4. Possible Threats to External Validity...40
4.5. Implications for Reducing Vulnerability to Extreme Heat in Ahmedabad...40-43
4.6. Implications for Future Research...43-47
5. Conclusion...47

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