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Weather, climate and health. Simon Lloyd London School of Hygiene and Tropical Medicine. Health outcomes influenced by climate: likely impacts of climate change. Figure 8.3: Ch 8 Human Health, IPCC 4AR. Health outcomes influenced by climate: likely impacts of climate change.
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Weather, climate and health Simon Lloyd London School of Hygiene and Tropical Medicine
Health outcomes influenced by climate: likely impacts of climate change Figure 8.3: Ch 8 Human Health, IPCC 4AR
Health outcomes influenced by climate: likely impacts of climate change • Impact on existing burden of disease • Various exposures of interest • At times, complex links Figure 8.3: Ch 8 Human Health, IPPC 4AR
Health outcomes influenced by climate: likely impacts of climate change Long term changes in means Daily or weekly changes Interannual variability Extreme weather events • Impact on existing burden of disease • Various exposures of interest • At times, complex links Figure 8.3: Ch 8 Human Health, IPPC 4AR
Health outcomes influenced by climate: likely impacts of climate change • Impact on existing burden of disease • Various exposures of interest • At times, complex links Figure 8.3: Ch 8 Human Health, IPPC 4AR
Exposure – outcome relationships Epidemiology at individual level Exposure Outcome Cardiovascular disease Smoking
Exposure – outcome relationships Epidemiology at individual level Exposure Outcome Cardiovascular disease Smoking • Weather/climate and health: • Exposure at population level • Pathway (often) indirect and complex • Impact moderated by vulnerability
Types of evidence for health effects Spatial studies • Climate as an explanatory variable in the distribution of the disease or the disease vector Temporal studies • short term (daily, weekly) changes • inter-annual climate variability • longer term (decadal) changes in the context of detecting early effects of climate change. Health impacts of individual extreme events • heat waves, floods, storms, droughts
Diarrhoea and average weather Diarrhoea rates
Diarrhoea and average weather Temperature Diarrhoea rates Mechanism: pathogen survival
Diarrhoea and average weather Temperature Diarrhoea rates High rainfall Mechanism: water supply contamination (water quality)
Diarrhoea and average weather Temperature Diarrhoea rates High rainfall Low rainfall Mechanism: use of unprotected water sources; reduced hygiene behaviour (water quantity)
Diarrhoea and average weather Temperature Water and sanitation Diarrhoea rates High rainfall Malnutrition Low rainfall etc. Climate type Socioeconomic conditions
Data Outcome Exposure Co-variates
Data Outcome Exposure Co-variates • Diarrhoea morbidity • Children under 5 years • Low and middle income countries • 36 study sites
Data Outcome Exposure Co-variates • Av. temperature over study period • Av. rainfall over study period • CRU TS 2.1 dataset • Underlying climate • Köppen climate classification
Data Outcome Exposure Co-variates • Socioeconomic conditions • Water and sanitation • Setting: urban, rural, slum
Study sites Lloyd, Kovats & Armstrong. Clim Res 2007; 34:119-27
Diarrhoea cases vs average weather Average monthly rainfall and log diarrhoea incidence in children aged 6-11 months, showing country Average temperature and log diarrhoea incidence in children aged 1 year, showing climate classification. Lloyd, Kovats & Armstrong. Clim Res 2007; 34:119-27
Regression results All models are adjusted for age group. Coefficients indicate the change in diarrhoea rate (episodes per child-year) for each: 10USD (in 2000 USDs) increase in GDP/capita; 10mm/month increase in average monthly rainfall; and, 1C increase in average temperature Lloyd, Kovats & Armstrong. Clim Res 2007; 34:119-27
Regression results Diarrhoea ↓4% (1 – 7%) for for each 10mm/month rainfall ↑ All models are adjusted for age group. Coefficients indicate the change in diarrhoea rate (episodes per child-year) for each: 10USD (in 2000 USDs) increase in GDP/capita; 10mm/month increase in average monthly rainfall; and, 1C increase in average temperature Lloyd, Kovats & Armstrong. Clim Res 2007; 34:119-27
Extreme events: coastal flooding • Spatial scale • WHO GBD regions
Extreme events: coastal flooding • Spatial scale • WHO GBD regions • Event and outcome data • International Emergency Disaster Database, University of Louvain, Belgium. EM-DAT
Initial estimates of impacts of extratropical & tropical cyclones, 1980 - 2007[EMDAT, 2008]
Initial estimates of impacts of extratropical & tropical cyclones, 1980 - 2007[EMDAT, 2008]
Initial estimates of impacts of extratropical & tropical cyclones, 1980 - 2007[EMDAT] 140 000 in a single event in 1991
Interannual variability: ENSO • Human impact of natural disasters increases during El Niño • ENSO associated with infectious diseases in some areas, esp cholera risk and malaria epidemics • ENSO and seasonal climate forecasts may have public health use
Interannual variability: ENSO • Human impact of natural disasters increases during El Niño • ENSO associated with infectious diseases in some areas, esp cholera risk and malaria epidemics • ENSO and seasonal climate forecasts may have public health use • Global disaster burden associated with El Niño over • a 30 year period (1964-1993) • Exposure: consensus El Niño years • Outcome: affected by a natural disaster
World population affected by natural disasters Rate per 1000 people, 1964-93 El Niño years Possible El Niño years Non-El Niño years Bouma, Kovats et al. Lancet 1997; 350:1435-8
World population affected by natural disasters Rate per 1000 people, 1964-93 • Strongest association between El Niño and drought (including food shortage and famine): • sub-Saharan Africa, South America, and South and West Asia Extreme rainfall and tropical cyclones: mixed effects by region Bouma, Kovats et al. Lancet 1997; 350:1435-8
El Niño: a natural disaster cycle? Bouma, Kovats et al. Lancet 1997; 350:1435-8
El Niño: a natural disaster cycle? 150 million people Bouma, Kovats et al. Lancet 1997; 350:1435-8
Climate and respiratory health in children Previous studies ↓ temperature range ↓ relative humidity range Asthma ↑ with: ↑ temperature in coldest month ↑ mean annual temperature
Data needs and queries • How well does data represent climate at particular study sites? • Are there areas that are not well represented? • Can data be used to quantify elements of events? • E.g. rainfall in floods; extent, intensity & duration of drought. • How well are ENSO events and their associated impacts on climate events represented?