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Too Hot!: an Epidemiological Investigation of Weather-Related Mortality in Rural India
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background

Most environmental epidemiological studies are conducted in high income settings. The association between ambient temperature and mortality has been studied worldwide, especially in developed countries. However, more research on the topic is necessary, particularly in India, given the limited evidence on the relationship between temperature and health in this country. The average global temperature is increasing, and it is estimated that it will go up further. The factors affecting vulnerability to heat-related mortality are not well studied. Therefore, identifying high-risk population subgroups is of particular importance given the rising temperature in India.

Objectives

This research aimed to investigate the association of daily mean temperature and rainfall with daily deaths (Paper I), examine the relationship of hot and cold days with total and cause-specific mortality (Paper II), assess the effects of heat and cold on daily mortality among different socio-demographic groups (Paper III) and estimate the effect of maximum temperature on years of life lost (Paper IV).

Methods

The Vadu Health and Demographic Surveillance System (HDSS) monitors daily deaths, births, in-out migration and other demographic trends in 22 villages from two administrative blocks in the rural Pune district of Maharashtra state, in western India. Daily deaths from Vadu HDSS and daily weather data (temperature and rainfall) from the Indian Meteorological Department were collected from 2003 through 2013. Verbal autopsy data were used to define causes of death and classified into four groups: non-infectious diseases, infectious diseases, external causes and unspecified causes of death. Socio-demographic groups were based on education, occupation, house type and land ownership. In all papers, time series regression models were applied as the basic approach; additionally, in Paper III, a case-crossover design and, in Paper IV, a distributed lag non-linear model (DLNM) were used.

Results

There was a significant association between daily temperature and mortality. Younger age groups (0-4 years) reported higher risk of mortality due to high and low temperature and heavy rainfall. In the working age group (20-59 years), mortality was significantly associated only with high temperature. Mortality due to non-infectious diseases was higher on hot days (>39°C), while mortality from infectious diseases and from external causes were not associated with hot or cold days. A higher heat-related total mortality was observed among men than in women. Mortality among residents with low education and those whose occupation was farming was associated with high temperature. We found a significant impact of high temperature on years of life lost, which confirms our results from the previous research (Papers I-III).

Conclusion

The study findings broadened our knowledge of the health impacts of environmental exposure by providing evidence on the risks related to ambient temperature in a rural population in India. More specifically, the study identified vulnerable population groups (working age groups, those of low education and farmers) in relation to high temperature. The adverse effect of heat on population is preventable if local human and technical capacities for risk communication and promoting adaptive behavior are built. Furthermore, it is necessary to increase residents’ awareness and prevention measures to tackle this public health challenge in rural populations.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 2016. , 65 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1825
Keyword [en]
Temperature, heat and cold, mortality, education, socioeconomic status, occupation, rural population, India
National Category
Medical and Health Sciences
Research subject
Public health
Identifiers
URN: urn:nbn:se:umu:diva-124811ISBN: 978-91-7601-529-2OAI: oai:DiVA.org:umu-124811DiVA: diva2:955590
Public defence
2016-09-21, Room 135, Family Medicine, Building 9A, Norrlands University Hospital, Norrlands University Hospital, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2016-08-31 Created: 2016-08-25 Last updated: 2016-09-16Bibliographically approved
List of papers
1. The short-term association of temperature and rainfall with mortality in Vadu Health and Demographic Surveillance System: a population level time series analysis.
Open this publication in new window or tab >>The short-term association of temperature and rainfall with mortality in Vadu Health and Demographic Surveillance System: a population level time series analysis.
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2012 (English)In: Global health action, ISSN 1654-9880, Vol. 5, 44-52 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Research in mainly developed countries has shown that some changes in weather are associated with increased mortality. However, due to the lack of accessible data, few studies have examined such effects of weather on mortality, particularly in rural regions in developing countries.

OBJECTIVE: In this study, we aimed to investigate the relationship between temperature and rainfall with daily mortality in rural India.

DESIGN: Daily mortality data were obtained from the Health and Demographic Surveillance System (HDSS) in Vadu, India. Daily mean temperature and rainfall data were obtained from a regional meteorological center, India Meteorological Department (IMD), Pune. A Poisson regression model was established over the study period (January 2003-May 2010) to assess the short-term relationship between weather variables and total mortality, adjusting for time trends and stratifying by both age and sex.

RESULT: Mortality was found to be significantly associated with daily ambient temperatures and rainfall, after controlling for seasonality and long-term time trends. Children aged 5 years or below appear particularly susceptible to the effects of warm and cold temperatures and heavy rainfall. The population aged 20-59 years appeared to face increased mortality on hot days. Most age groups were found to have increased mortality rates 7-13 days after rainfall events. This association was particularly evident in women.

CONCLUSION: We found the level of mortality in Vadu HDSS in rural India to be highly affected by both high and low temperatures and rainfall events, with time lags of up to 2 weeks. These results suggest that weather-related mortality may be a public health problem in rural India today. Furthermore, as changes in local climate occur, adaptation measures should be considered to mitigate the potentially negative impacts on public health in these rural communities.

National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-65771 (URN)10.3402/gha.v5i0.19118 (DOI)23195513 (PubMedID)
Available from: 2013-02-11 Created: 2013-02-11 Last updated: 2016-08-25Bibliographically approved
2. Impact of Heat and Cold on Total and Cause-Specific Mortality in Vadu HDSS: A Rural Setting in Western India
Open this publication in new window or tab >>Impact of Heat and Cold on Total and Cause-Specific Mortality in Vadu HDSS: A Rural Setting in Western India
2015 (English)In: International Journal of Environmental Research and Public Health, ISSN 1660-4601, E-ISSN 1660-4601, Vol. 12, no 12, 15298-15308 p.Article in journal (Refereed) Published
Abstract [en]

Many diseases are affected by changes in weather. There have been limited studies, however, which have examined the relationship between heat and cold and cause-specific mortality in low and middle-income countries. In this study, we aimed to estimate the effects of heat and cold days on total and cause-specific mortality in the Vadu Health and Demographic Surveillance System (HDSS) area in western India. We used a quasi-Poisson regression model allowing for over-dispersion to examine the association of total and cause-specific mortality with extreme high (98th percentile, >39 °C) and low temperature (2nd percentile, <25 °C) over the period January 2003 to December 2012. Delays of 0 and 0-4 days were considered and relative risks (RR) with 95% confidence intervals (CI) were calculated. Heat was significantly associated with daily deaths by non-infectious diseases (RR = 1.57; CI: 1.18-2.10). There was an increase in the risk of total mortality in the age group 12-59 years on lag 0 day (RR = 1.43; CI: 1.02-1.99). A high increase in total mortality was observed among men at lag 0 day (RR = 1.38; CI: 1.05-1.83). We did not find any short-term association between total and cause-specific mortality and cold days. Deaths from neither infectious nor external causes were associated with heat or cold. Our results showed a strong and rather immediate relationship between high temperatures and non-infectious disease mortality in a rural population located in western India, during 2003-2012. This study may be used to develop targeted interventions such as Heat Early Warning Systems in the area to reduce mortality from extreme temperatures.

Place, publisher, year, edition, pages
Modern Scientific Press, 2015
Keyword
heat, cold, temperature, mortality, cause-specific mortality, India
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-112706 (URN)10.3390/ijerph121214980 (DOI)000367539000026 ()26633452 (PubMedID)
Available from: 2015-12-14 Created: 2015-12-14 Last updated: 2016-08-25Bibliographically approved
3. Socio-environmental factors associated with heat and cold related mortality in Vadu HDSS, western India: A  Population based case-crossover study design
Open this publication in new window or tab >>Socio-environmental factors associated with heat and cold related mortality in Vadu HDSS, western India: A  Population based case-crossover study design
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(English)Article in journal (Refereed) Submitted
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-124538 (URN)
Available from: 2016-08-15 Created: 2016-08-15 Last updated: 2016-08-25
4. Impact of temperture on years of life lost in high, middle, and low-income settings - a multi-site study across four continents
Open this publication in new window or tab >>Impact of temperture on years of life lost in high, middle, and low-income settings - a multi-site study across four continents
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(English)Article in journal (Refereed) Submitted
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-124540 (URN)
Available from: 2016-08-15 Created: 2016-08-15 Last updated: 2016-08-25

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