CLIMATE VARIABILITY AND DISEASE PATTERNS IN TWO SOUTH EASTERN CARIBBEAN COUNTRIES. Dharmaratne Amarakoon, Roxann Stennett and Anthony Chen

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1 1 CLIMATE VARIABILITY AND DISEASE PATTERNS IN TWO SOUTH EASTERN CARIBBEAN COUNTRIES Dharmaratne Amarakoon, Roxann Stennett and Anthony Chen Climate Studies Group Mona, Department of Physics, University of the West Indies, Kingston 7 Jamaica (dharmaratne.amarakoon@uwimona.edu.jm; roxann.stennett@uwimona.edu.jm; anthony.chen@uwimona.edu.jm) Abstract. A preliminary study of climate variability and patterns of diseases in Barbados and St. Lucia was carried out. Climate parameters analyzed were temperature, rainfall, relative humidity, and Sahara dust concentration. Analysis of daily temperature data for Barbados indicated that percent of days having very warm (>90 th percentile on temperature scale) maximum or minimum temperatures increased significantly while the percent of days with very cold (<10 th percentile on temperature scale) temperatures decreased. Temporal trends of monthly and annual mean temperatures showed statistically significant (r = 0.21, p = 4.85E-05 and r = 0.459, p = 0.009, respectively) increases. Analysis of rainfall data indicated that the index R95T (percentage of total rainfall due to events above the 95 th percentile on rainfall scale- a measure of extreme rainfall) and also the percent of dry days (days < 1 mm rainfall) increased slowly. The temporal trend observed in R95T, however, was not statistically significant (p = 0.371) where as that of the percent of dry days was statistically significant (r = and p= 0.054). Study of the temporal trend of monthly mean temperatures for St. Lucia indicated that there was a slow warming trend but very significant (r = and p = 3.57E-09). Analysis of rainfall data indicated that the annual rainfall show an increase with less significance (r = and p = 0.096) for the period 1974 to 1999, but a fairly significant decrease (r = and p = 0.074) during the last one and a half decades ( ). Data for Sahara dust concentration were common to Barbados and St. Lucia, and the analysis indicated that the monthly concentrations increased (r = and p = 0.052) with a significant association (r = and p = 1.72E-07) with Barbados monthly maximum temperature and St. Lucia monthly mean temperature (r = and p = 1.28E-07). Overall, the analysis of climate data signaled a noticeable warming trend in Barbados and St. Lucia and a weaker trend towards less abundance in rainfall. Results of the analysis of disease data revealed that most of the diseases (Dengue, Asthma, Bronchitis, Respiratory Tract Infections, Diarrheal illnesses) exhibited seasonal patterns. Correlations of disease data with climate data indicated significant (moderate r and low p values) associations of Dengue with temperature and rainfall; Asthma, Bronchitis and Respiratory Tract Infections with temperature, relative humidity and Sahara dust; Diarrheal illnesses with temperature and rainfall. These observations were more pronounced in Barbados. Overall, temperature appeared to be the most associating climate parameter, positively after some lag. Based on the trends in the climate parameters observed in this work, possibility exists for the South Eastern Caribbean to experience higher incidences of Dengue, Respiratory diseases and Diarrheal illnesses in the present century.

2 2 Introduction Climate change and variability, and its impacts on human health are areas of research that have been receiving very much attention of scientists and policy makers all around the world over the last decade or so. The subject of climate change and variability is older than the subject of its impacts. The subject of climate change and variability, and its impacts on human health, however, is new to the Caribbean region. Recently published studies (Peterson and Taylor et al., 2002; Chen and Taylor, 2002) indicate that the climate in the Caribbean is exhibiting a changing trend. These studies predict a warming trend in the Caribbean, drier than normal conditions with warmer temperatures in the latter half of El Niño years, and increase in precipitation in the early part of the following year. In the area of climate impacts on health in the Caribbean region, a few studies appear to exist, which are mainly attempts to study the climate impacts on Dengue fever (Wgbreit, 1997; Campione-Piccardo et al., 2003; Amarakoon et al., 2004; Rawlins et al., 2004) and impacts of Sahara dust on Asthma (Blades et al., 1997; Gyan et al., 2002) in some parts of the Caribbean. Findings of these studies signal an association of climate with Dengue and Asthma. In this paper, we attempt to provide more details on the nature of association of diseases with climate variability. Attention was focused on two countries, namely Barbados and St. Lucia, in the South Eastern Caribbean. Climate variability of these two countries was studied, patterns of some diseases (Dengue, Asthma, Bronchitis, Respiratory Tract Infections, Diarrheal Illnesses) were examined, and statistical analysis was performed to obtain information on the degree of correlation between the diseases and climate parameters (temperature, precipitation, relative humidity, Sahara dust concentration), including lag. Data and methods Climate parameters analyzed were temperature, rainfall, relative humidity, and Sahara dust concentration. Long term temperature and precipitation data were obtained from the data depository of the Climate Studies Group Mona (CSGM) at the Department of Physics, the University of the West Indies, Mona Campus, Jamaica and were supplemented by the data from the Caribbean Environmental Health Institute (CEHI) in St. Lucia. Barbados rainfall and temperature data were available on a daily or monthly basis and spanned the period 1969 to 2002 while data for St. Lucia were monthly and spanned the period 1974 to In both countries, relative humidity (from 2000 to 2002) and Sahara dust concentration data (from 1996 to 2002) were monthly. Relative humidity and Sahara dust concentration data were obtained from CEHI in St. Lucia. Disease data used in this work were monthly and belonged to the period 2000 to Disease data were obtained from CEHI in St. Lucia. Data for Sahara dust concentration were common to Barbados and St. Lucia. Data analysis consisted of time series analysis of climate and disease variables, calculating and investigating the variability of precipitation and temperature indices, creating scatter plots and charts of diseases against climate variables, regression analysis including ANOVA, and lag correlations. Results presented in this paper are at national levels in Barbados and St. Lucia, and no particular attention was focused on individual stations such as health centres and polyclinics.

3 3 Results obtained were used to understand the patterns of diseases, and the degree of dependence of disease occurrences on the climate. Results Results obtained in this study are given in tables 1 to 5, and figures 1 to 10. Tables contain results for correlation of disease occurrences with climate parameters. Figures presented are mainly for Barbados, but generally are representatives of the scenarios in Barbados and St. Lucia (South Eastern Caribbean region). Figure1 and 2 indicate that in Barbados, percent of days having very warm (> 90 th percentile on temperature scale) maximum or minimum temperatures have increased during the last three decades while the percent of days with very cold (< 10 th percentile on temperature scale) have decreased. Correlation results are very significant in relation to minimum temperature, and for the case of percent of days < 10 th percentile in maximum temperature. Study of temporal trends of monthly and annual mean temperatures in Barbados indicated slow but statistically significant increases. Correlation results were r = 0.21 and p = 4.85E-05 for monthly means, and r = and p = for annual means. Long term daily climate data were not available for St. Lucia, but monthly data were available. Study of the temporal trend of monthly mean temperatures for St. Lucia revealed a slow but a significant temperature increase (r = 0.317, and p = 3.57E-09). Overall, results from the analysis of temperature data signaled a noticeable warming trend in Barbados and St. Lucia. Figure 3, which is for Barbados, shows that the precipitation index R95T which is a measure of extreme rainfall and represents the percentage of total rainfall due to events above the 95 th percentile on rainfall scale has increased over the last three decades although not statistically significant (r = and p = 0.371). The dip in the year 1980 was because, a large amount of daily data in 1980 were missing. The percentage of data available in 1980 was only 22%. In the correlation analysis year 1980 was ignored. Figure 4, which is again for Barbados, shows that the percent of dry days (percent of days < 1 mm- rainfall) has increased slowly but statistically significant (r= and p = 0.054). In St. Lucia, analysis of rainfall data revealed that the annual rainfall has increased with low significance (r = and p = ) over the period 1974 to 1999, but has decreased fairly significantly (r = and p = 0.074) over the last one and a half decades ( ). Overall, results from the analysis of rainfall data suggested a weak trend towards less abundance in rainfall combined with a less significant increase in extreme rainfall events. Figure 5 shows the monthly variability of Sahara dust (SD) concentration and Barbados maximum temperature. The graphs indicate that variability of SD concentration is seasonal, low in the early half of the year and peaks up in summer and attenuates as year end is approached. The SD pattern follows the temperature pattern fairly closely. Detail analysis revealed that monthly concentration over the period January, 1996 to October, 2001 has increased slowly (r = and p = 0.052). Further, the results showed that SD concentration correlated reasonably well with Barbados monthly maximum temperature (r = and p = 1.72E-07) and St. Lucia monthly mean temperature (r = and p = 1.28E-07). Overall, results appeared to indicate the fact that, during warmer summer months, the associated strong atmospheric circulations may be intensifying the flow of Sahara dust and vice versa in the less warm months.

4 4 Figures 6 to 9 presents monthly variability of reported Dengue cases, Respiratory Tract Infections (RTI) and Asthma (0-5 yrs). The term standardized anomaly as used in this work refers to: (observed value of a parameter- average value)/standard deviation. One feature to be noted is seasonality. The diseases appear to peak in the latter half of the year after the summer warming, rain, and when the colder season is approaching. This was the case with many other diseases, including Bronchitis and Diarrheal illnesses. Also noticeable is the lag between disease peaks and climate parameter peaks. Tables 1 to 5 present the results (r and p values), based on the correlation studies between the diseases and the climate parameters performed. The results for which p is at least greater than 0.1 (90% confidence level) are given in these tables. From the results in the tables, it appears that the climate parameters show significant association with the diseases. Associations are negative or positive depending on the amount of lag. Overall, temperature appears to be the most associating parameter followed by Sahara dust. Discussion and conclusion We presented preliminary results from a study of climate impacts on health. The diseases considered were Dengue, Asthma, Bronchitis, Respiratory Tract Infections (RTI) and Diarrheal illnesses. Results revealed that diseases exhibit a seasonal pattern with significant association with climate parameters. Dengue showed association with temperature and rainfall; respiratory diseases (Asthma, Bronchitis, RTI ) showed association with temperature, relative humidity and Sahara dust; Diarrheal illnesses with temperature and rainfall. A common feature observed was that the climate parameters appear to have influenced positively after a certain lag. In the case of Dengue this feature is in agreement with the findings of Wegbreit (1997) for Trinidad. His findings had indicated that it takes six months for environmental conditions, as measured by temperature alone, to affect Dengue incidence. He has attributed this observation to temperature s influence on the life cycle of the mosquito and or viral replication rates. The degree of association of Dengue with rainfall, seen in this work, also closely agrees with what was observed by Wegbreit, that precipitation six months prior to reporting Dengue may reduce Dengue incidence rates. This agreement is seen, especially when the correlation results for St. Lucia is examined. However, a statistically significant relationship of precipitation and Dengue incidence had not been observed by Wegbreit. In our work, the relationships observed were statistically significant, especially in Barbados indicating that precipitation does influence Dengue incidences. From the correlation results for respiratory diseases it is clear that except relative humidity other parameters (temperature, Sahara dust) influence positively after a few months of lag. When r and p values are considered, influence of temperature appears to be stronger than others, followed by Sahara dust. The lag of a few months seen is acceptable considering the fact that one of the triggers of respiratory diseases is weather change (warm to cold), especially with Asthma, and temperature changes are strongly associated with seasonal weather changes. Other common triggers are: local dust, smoke, pollen, and ground level ozone. The degree of influence of temperature change can be understood by an examination of figures 9 (Asthma in St. Lucia for 0-5yrs group) and 10 (Daily maximum temperature variation from November February 2002 in St. Lucia). A gradual, but a very significant (r = and p = 6.72E-30), decrease in temperature can be observed which corresponds to the occurrence of the Asthma peak in

5 5 As conclusive remarks we may state that our findings are based on a limited amount of health data (3 years, ). As such, an in-depth study is required, with longer time series of data, to reinforce our findings. Also, in the case of respiratory diseases, no attempt was made to study the influence of other triggers such as local dust, smoke, pollen, ground level ozone because of unavailability of data. But based on the trends observed in temperature, precipitation and Sahara dust we may state that possibility exists for the South Eastern Caribbean to experience higher incidences of Dengue, Respiratory diseases and Diarrheal illnesses in the present century. References 1. Peterson TC, Taylor MA, Demeritte R, Duncombe DL, Burton S, Thompson F et al. Recent changes in climate extremes in the Caribbean region. Journal of Geophysical Research 2002; 107(D21), ACL 16: Chen AA, Taylor MA. Investigating the link between early season Caribbean rainfall and the El Niño+1 year. International Journal of Climatology 2002; 22: Wegbreit Jeny. The Possible Effects of Temperature and Precipitation on Dengue Morbidity in Trinidad and Tobago: A Retrospective Longitudinal Study. University of Michigan, Campione-Piccardo J, Ruben M, Vaughan H, Morris-Glasgow V. Dengue Viruses in the Caribbean. Twenty Years of Dengue Virus Isolates from the Caribbean Epidemiology Centre. West Indian Med J 2003; 52(3): Amarakoon AMD, Chen AA, Rawlins SC, Taylor MA. Dengue Epidemics-its association with precipitation and temperature, and its seasonality in some Caribbean countries. CHRC 49 th annual conference, Grenada, April Rawlins SC, Chen A, Ivey M, Amarakoon D, Polson K. The Impact of Climate Change/Variability events on the occurrence of Dengue Fever in parts of the Caribbean: a retrospective study for the period CHRC 49 th annual conference, Grenada, April Blades E, Naidu R, Mathison, G. The Microbiological Analysis of Sahara dust and its association with Asthma in Barbados. Cave Hill, Barbados, Gyan K, Henry W, Lacaille s, Laloo A, Lamsee-Ebanks C, S McKay S, Antoine RM, Monteil MA. African dust clouds are associated with increased paediatric asthma. Accident and Emergency admissions on the Caribbean island of Trinidad. St. Augustine, UWI, 2002 Acknowledgements The authors wish to thank the staff at the Caribbean Environmental Health Institute in St. Lucia for providing disease and some climate data used in this work.

6 6 Table 1. Correlation results of Dengue with temperature and rainfall Barbados Rainfall Max Temperature Lag r p r p` (months) E St. Lucia Rainfall Mean Temperature Lag r-value p-value r-value p-value (months) Table 2a. Correlation results of Asthma with temperature, relative humidity and Sahara dust for Barbados 0-5yrs Relative Humidity MaxTemperature Sahara Dust Lag r p r p r p (months) yrs yrs No significant correlation

7 7 >50yrs Table 2b. Correlation results of Asthma with temperature, relative humidity and Sahara dust for St. Lucia 0-5yrs Relative Humidity Mean Temperature Sahara Dust Lag (months) r p r p r p E yrs yrs >50yrs

8 8 Table 3a. Correlation results of Bronchitis with temperature, relative humidity and Sahara dust for Barbados 0-5yrs Relative Humidity Max Temperature Sahara Dust Lag r p r p r p (months) yrs yrs >50yrs

9 9 Table 3b. Correlation results of Bronchitis with temperature, relative humidity and Sahara dust for St. Lucia 0-5yrs Relative Humidity Mean Temperature Sahara Dust Lag r p r p r p (months) E E E E E E yrs yrs >50yrs E E

10 10 Table 4. Correlation results of Respiratory Tract Infections (RTI) with temperature, relative humidity, rainfall and Sahara dust in Barbados (BB) and St. Lucia. BB Lag (month s) Relative Humidity Temperature (Max/Mean) Sahara Dust Rainfall r p r p r p r p St. Lucia E E E E E-04 Table 5. Correlation results of Diarrheal illnesses with temperature and rainfall in Barbados Lag (months) Max Temperature Rainfall r p r p` E E E

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St Lucia. General Climate. Recent Climate Trends. UNDP Climate Change Country Profiles. Temperature. Precipitation

St Lucia. General Climate. Recent Climate Trends. UNDP Climate Change Country Profiles. Temperature. Precipitation UNDP Climate Change Country Profiles St Lucia C. McSweeney 1, M. New 1,2 and G. Lizcano 1 1. School of Geography and Environment, University of Oxford. 2. Tyndall Centre for Climate Change Research http://country-profiles.geog.ox.ac.uk