Search tips
Search criteria

Results 1-12 (12)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
1.  The Impact of Climatic Risk Factors on the Prevalence, Distribution, and Severity of Acute and Chronic Trachoma 
Background and Objectives
Trachoma is the most common cause of infectious blindness. Hot, dry climates, dust and water scarcity are thought to be associated with the distribution of trachoma but the evidence is unclear. The aim of this study was to evaluate the epidemiological evidence regarding the extent to which climatic factors explain the current prevalence, distribution, and severity of acute and chronic trachoma. Understanding the present relationship between climate and trachoma could help inform current and future disease elimination.
A systematic review of peer-reviewed literature was conducted to identify observational studies which quantified an association between climate factors and acute or chronic trachoma and which met the inclusion and exclusion criteria. Studies that assessed the association between climate types and trachoma prevalence were also reviewed.
Only eight of the 1751 papers retrieved met the inclusion criteria, all undertaken in Africa. Several papers reported an association between trachoma prevalence and altitude in highly endemic areas, providing some evidence of a role for temperature in the transmission of acute disease. A robust mapping study found strong evidence of an association between low rainfall and active trachoma. There is also consistent but weak evidence that the prevalence of trachoma is higher in savannah-type ecological zones. There were no studies on the effect of climate in low endemic areas, nor on the effect of dust on trachoma.
Current evidence on the potential role of climate on trachoma distribution is limited, despite a wealth of anecdotal evidence. Temperature and rainfall appear to play a role in the transmission of acute trachoma, possibly mediated through reduced activity of flies at lower temperatures. Further research is needed on climate and other environmental and behavioural factors, particularly in arid and savannah areas. Many studies did not adequately control for socioeconomic or environmental confounders.
Author Summary
Trachoma – the leading cause of infectious blindness – is spread through contact with infected persons by hands and towels, and by ‘eye-seeking flies.’ Trachoma prevalence is high in areas characterised by poverty, inadequate water supply, and poor sanitation. Trachoma is controlled by the SAFE strategy: S = surgery to the upper eyelids; A = antibiotics for active infection; F = facial cleanliness; and E = environmental improvement. In this study we reviewed the scientific literature to assess the extent to which climatic factors (e.g., rainfall, heat, dust, altitude) influence trachoma distribution. A systematic review of the literature found eight papers that measured an association between a climatic factor and trachoma in children or adults. Several studies reported that trachoma is less common at higher altitudes, indicating that temperature may play a role in trachoma transmission. Some studies also reported that trachoma is higher in areas with low rainfall, which is consistent with anecdotal evidence that trachoma is associated with dry environments.
PMCID: PMC3820701  PMID: 24244768
2.  Time-series analysis of weather and mortality patterns in Nairobi's informal settlements 
Global Health Action  2012;5:10.3402/gha.v5i0.19065.
Many studies have established a link between weather (primarily temperature) and daily mortality in developed countries. However, little is known about this relationship in urban populations in sub-Saharan Africa.
The objective of this study was to describe the relationship between daily weather and mortality in Nairobi, Kenya, and to evaluate this relationship with regard to cause of death, age, and sex.
We utilized mortality data from the Nairobi Urban Health and Demographic Surveillance System and applied time-series models to study the relationship between daily weather and mortality for a population of approximately 60,000 during the period 2003–2008. We used a distributed lag approach to model the delayed effect of weather on mortality, stratified by cause of death, age, and sex.
Increasing temperatures (above 75th percentile) were significantly associated with mortality in children and non-communicable disease (NCD) deaths. We found all-cause mortality of shorter lag of same day and previous day to increase by 3.0% for a 1 degree decrease from the 25th percentile of 18°C (not statistically significant). Mortality among people aged 50+ and children aged below 5 years appeared most susceptible to cold compared to other age groups. Rainfall, in the lag period of 0–29 days, increased all-cause mortality in general, but was found strongest related to mortality among females. Low temperatures were associated with deaths due to acute infections, whereas rainfall was associated with all-cause pneumonia and NCD deaths.
Increases in mortality were associated with both hot and cold weather as well as rainfall in Nairobi, but the relationship differed with regard to age, sex, and cause of death. Our findings indicate that weather-related mortality is a public health concern for the population in the informal settlements of Nairobi, Kenya, especially if current trends in climate change continue.
PMCID: PMC3509073  PMID: 23195509
time-series; temperature; rainfall; mortality; climate; urban
3.  Drinking Water Salinity and Maternal Health in Coastal Bangladesh: Implications of Climate Change 
Environmental Health Perspectives  2011;119(9):1328-1332.
Background: Drinking water from natural sources in coastal Bangladesh has become contaminated by varying degrees of salinity due to saltwater intrusion from rising sea levels, cyclone and storm surges, and upstream withdrawal of freshwater.
Objective: Our objective was to estimate salt intake from drinking water sources and examine environmental factors that may explain a seasonal excess of hypertension in pregnancy.
Methods: Water salinity data (1998–2000) for Dacope, in rural coastal Bangladesh, were obtained from the Centre for Environment and Geographic Information System in Bangladesh. Information on drinking water sources, 24-hr urine samples, and blood pressure was obtained from 343 pregnant Dacope women during the dry season (October 2009 through March 2010). The hospital-based prevalence of hypertension in pregnancy was determined for 969 pregnant women (July 2008 through March 2010).
Results: Average estimated sodium intakes from drinking water ranged from 5 to 16 g/day in the dry season, compared with 0.6–1.2 g/day in the rainy season. Average daily sodium excretion in urine was 3.4 g/day (range, 0.4–7.7 g/day). Women who drank shallow tube-well water were more likely to have urine sodium > 100 mmol/day than women who drank rainwater [odds ratio (OR) = 2.05; 95% confidence interval (CI), 1.11–3.80]. The annual hospital prevalence of hypertension in pregnancy was higher in the dry season (OR = 12.2%; 95% CI, 9.5–14.8) than in the rainy season (OR = 5.1%; 95% CI, 2.91–7.26).
Conclusions: The estimated salt intake from drinking water in this population exceeded recommended limits. The problem of saline intrusion into drinking water has multiple causes and is likely to be exacerbated by climate change–induced sea-level rise.
PMCID: PMC3230389  PMID: 21486720
climate change; hypertension; maternal health; pregnancy; salinity intrusion
4.  Long-term effects of flooding on mortality in England and Wales, 1994-2005: controlled interrupted time-series analysis 
Environmental Health  2011;10:11.
Limited evidence suggests that being flooded may increase mortality and morbidity among affected householders not just at the time of the flood but for months afterwards. The objective of this study is to explore the methods for quantifying such long-term health effects of flooding by analysis of routine mortality registrations in England and Wales.
Mortality data, geo-referenced by postcode of residence, were linked to a national database of flood events for 1994 to 2005. The ratio of mortality in the post-flood year to that in the pre-flood year within flooded postcodes was compared with that in non-flooded boundary areas (within 5 km of a flood). Further analyses compared the observed number of flood-area deaths in the year after flooding with the number expected from analysis of mortality trends stratified by region, age-group, sex, deprivation group and urban-rural status.
Among the 319 recorded floods, there were 771 deaths in the year before flooding and 693 deaths in the year after (post-/pre-flood ratio of 0.90, 95% CI 0.82, 1.00). This ratio did not vary substantially by age, sex, population density or deprivation. A similar post-flood 'deficit' of deaths was suggested by the analyses based on observed/expected deaths.
The observed post-flood 'deficit' of deaths is counter-intuitive and difficult to interpret because of the possible influence of population displacement caused by flooding. The bias that might arise from such displacement remains unquantified but has important implications for future studies that use place of residence as a marker of exposure.
PMCID: PMC3042000  PMID: 21288358
5.  The impact of heat waves on mortality in 9 European cities: results from the EuroHEAT project 
Environmental Health  2010;9:37.
The present study aimed at developing a standardized heat wave definition to estimate and compare the impact on mortality by gender, age and death causes in Europe during summers 1990-2004 and 2003, separately, accounting for heat wave duration and intensity.
Heat waves were defined considering both maximum apparent temperature and minimum temperature and classified by intensity, duration and timing during summer. The effect was estimated as percent increase in daily mortality during heat wave days compared to non heat wave days in people over 65 years. City specific and pooled estimates by gender, age and cause of death were calculated.
The effect of heat waves showed great geographical heterogeneity among cities. Considering all years, except 2003, the increase in mortality during heat wave days ranged from + 7.6% in Munich to + 33.6% in Milan. The increase was up to 3-times greater during episodes of long duration and high intensity. Pooled results showed a greater impact in Mediterranean (+ 21.8% for total mortality) than in North Continental (+ 12.4%) cities. The highest effect was observed for respiratory diseases and among women aged 75-84 years. In 2003 the highest impact was observed in cities where heat wave episode was characterized by unusual meteorological conditions.
Climate change scenarios indicate that extreme events are expected to increase in the future even in regions where heat waves are not frequent. Considering our results prevention programs should specifically target the elderly, women and those suffering from chronic respiratory disorders, thus reducing the impact on mortality.
PMCID: PMC2914717  PMID: 20637065
6.  Current and future climate- and air pollution-mediated impacts on human health 
Environmental Health  2009;8(Suppl 1):S8.
We describe a project to quantify the burden of heat and ozone on mortality in the UK, both for the present-day and under future emission scenarios.
Mortality burdens attributable to heat and ozone exposure are estimated by combination of climate-chemistry modelling and epidemiological risk assessment. Weather forecasting models (WRF) are used to simulate the driving meteorology for the EMEP4UK chemistry transport model at 5 km by 5 km horizontal resolution across the UK; the coupled WRF-EMEP4UK model is used to simulate daily surface temperature and ozone concentrations for the years 2003, 2005 and 2006, and for future emission scenarios. The outputs of these models are combined with evidence on the ozone-mortality and heat-mortality relationships derived from epidemiological analyses (time series regressions) of daily mortality in 15 UK conurbations, 1993-2003, to quantify present-day health burdens.
During the August 2003 heatwave period, elevated ozone concentrations > 200 μg m-3 were measured at sites in London and elsewhere. This and other ozone photochemical episodes cause breaches of the UK air quality objective for ozone. Simulations performed with WRF-EMEP4UK reproduce the August 2003 heatwave temperatures and ozone concentrations. There remains day-to-day variability in the high ozone concentrations during the heatwave period, which on some days may be explained by ozone import from the European continent.
Preliminary calculations using extended time series of spatially-resolved WRF-EMEP4UK model output suggest that in the summers (May to September) of 2003, 2005 & 2006 over 6000 deaths were attributable to ozone and around 5000 to heat in England and Wales. The regional variation in these deaths appears greater for heat-related than for ozone-related burdens.
Changes in UK health burdens due to a range of future emission scenarios will be quantified. These future emissions scenarios span a range of possible futures from assuming current air quality legislation is fully implemented, to a more optimistic case with maximum feasible reductions, through to a more pessimistic case with continued strong economic growth and minimal implementation of air quality legislation.
Elevated surface ozone concentrations during the 2003 heatwave period led to exceedences of the current UK air quality objective standards. A coupled climate-chemistry model is able to reproduce these temperature and ozone extremes. By combining model simulations of surface temperature and ozone with ozone-heat-mortality relationships derived from an epidemiological regression model, we estimate present-day and future health burdens across the UK. Future air quality legislation may need to consider the risk of increases in future heatwaves.
PMCID: PMC2796504  PMID: 20102593
7.  National Assessment of Human Health Effects of Climate Change in Portugal: Approach and Key Findings 
Environmental Health Perspectives  2006;114(12):1950-1956.
In this study we investigated the potential impact of climate change in Portugal on heat-related mortality, air pollution–related health effects, and selected vectorborne diseases. The assessment used climate scenarios from two regional climate models for a range of future time periods. The annual heat-related death rates in Lisbon may increase from between 5.4 and 6 per 100,000 in 1980–1998 to between 8.5 and 12.1 by the 2020s and to a maximum of 29.5 by the 2050s, if no adaptations occur. The projected warmer and more variable weather may result in better dispersion of nitrogen dioxide levels in winter, whereas the higher temperatures may reduce air quality during the warmer months by increasing tropospheric ozone levels. We estimated the future risk of zoonoses using ecologic scenarios to describe future changes in vectors and parasites. Malaria and schistosomiasis, which are currently not endemic in Portugal, are more sensitive to the introduction of infected vectors than to temperature changes. Higher temperatures may increase the transmission risk of zoonoses that are currently endemic to Portugal, such as leishmaniasis, Lyme disease, and Mediterranean spotted fever.
PMCID: PMC1764176  PMID: 17185290
climate change; disease; health impact assessment; Portugal
8.  Cross-sectional survey of older peoples' views related to influenza vaccine uptake 
BMC Public Health  2006;6:249.
The population's views concerning influenza vaccine are important in maintaining high uptake of a vaccine that is required yearly to be effective. Little is also known about the views of the more vulnerable older population over the age of 74 years.
A cross-sectional survey of community dwelling people aged 75 years and over wh, previous participant was conducted using a postal questionnaire. Responses were analysed by vaccine uptake records and by socio-demographic and medical factors.
85% of men and 75% of women were vaccinated against influenza in the previous year. Over 80% reported being influenced by a recommendation by a health care worker. The most common reason reported for non uptake was good health (44%), or illness considered to be due to the vaccine (25%). An exploration of the crude associations with socio-economic status suggested there may be some differences in the population with these two main reasons. 81% of people reporting good health lived in owner occupied housing with central heating vs. 63% who did not state this as a reason (p = 0.04), whereas people reporting ill health due to the vaccine was associated with poorer social circumstances. 11% lived in the least deprived neighbourhood compared to 36% who did not state this as a reason (p = 0.05) and were less likely to be currently married than those who did not state this as a reason (25% vs 48% p = 0.05).
Vaccine uptake was high, but non uptake was still noted in 1 in 4 women and 1 in 7 men aged over 74 years. Around 70% reported they would not have the vaccine in the following year. The divergent reasons for non-uptake, and the positive influence from a health care worker, suggests further uptake will require education and encouragement from a health care worker tailored towards the different views for not having influenza vaccination. Non-uptake of influenza vaccine because people viewed themselves as in good health may explain the modest socio-economic differentials in influenza vaccine uptake in elderly people noted elsewhere. Reporting of ill-health due to the vaccine may be associated with a different, poorer background.
PMCID: PMC1621069  PMID: 17034625
9.  Climate change and health 
PMCID: PMC1188198
10.  Effect of influenza vaccination on excess deaths occurring during periods of high circulation of influenza: cohort study in elderly people 
BMJ : British Medical Journal  2004;329(7467):660.
Objective To estimate the protection against death provided by vaccination against influenza.
Design Prospective cohort follow up supplemented by weekly national counts of influenza confirmed in the community.
Setting Primary care.
Participants 24 535 patients aged over 75 years from 73 general practices in Great Britain.
Main outcome measure Death.
Results In unvaccinated members of the cohort daily all cause mortality was strongly associated with an index of influenza circulating in the population (mortality ratio 1.16, 95% confidence interval 1.04 to 1.29 at 90th centile of circulating influenza). The association was strongest for respiratory deaths but was also present for cardiovascular deaths. In contrast, in vaccinated people mortality from any cause was not associated with circulating influenza. The difference in patterns between vaccinated and unvaccinated people could not easily be due to chance (P = 0.02, all causes).
Conclusions This study, using a novel and robust approach to control for confounding, provides robust evidence of a protective effect on mortality of vaccination against influenza.
PMCID: PMC517645  PMID: 15313884
11.  Trends in influenza vaccination uptake among people aged over 74 years, 1997–2000: Survey of 73 general practices in Britain 
Influenza vaccination policy for elderly people in Britain has changed twice since 1997 to increase protection against influenza but there is no information available on how this has affected vaccine uptake, and socioeconomic variation therein, among people aged over 74 years.
Vaccination information for 1997–2000 was collected directly from general practices taking part in a MRC-funded Trial of the Assessment and Management of Older People in the Community. This was linked to information collected during assessments carried out as part of the Trial. Regression modelling was used to assess relative probabilities (as relative risks, RR) of having vaccination according to year, gender, age, area and individual socioeconomic characteristics.
Out of 106 potential practices, 73 provided sufficient information to be included in the analysis. Uptake was 48% (95% CI 45%, 55%) in 1997 and did not increase substantially until 2000 when the uptake was a third higher at 63% (50%, 66%). Vaccination uptake was lower among women than men (RR 0.9), people aged 85 or more compared to people aged under 80 (RR 0.9), those in the most deprived areas (RR 0.8) compared to the least deprived, and was relatively high for those in owner-occupied homes with central heating compared to other non-supported housing (RR for remainder = 0.9). This pattern did not change over the years studied.
Increased uptake in 2000 may have resulted from the additional financial resources given to practices; it was not at the expense of more disadvantaged socioeconomic groups but nor did they benefit disproportionately.
PMCID: PMC421730  PMID: 15099402

Results 1-12 (12)