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Spatial variation in hyperthermia emergency department visits among those with employer-based insurance in the United States - a case-crossover analysis.

Saha S, Brock JW, Vaidyanathan A, Easterling DR, Luber G - Environ Health (2015)

Bottom Line: Random effects meta-analysis was used to combine the odds ratios for 94 Metropolitan Statistical Areas (MSA) to examine the spatial variation by eight latitude categories and nine U.S. climate regions.These results were insensitive to the inclusion of air pollution measures.The meta-analysis showed higher odds ratios of hyperthermia ED visit in the central and the northern parts of the country compared to the south and southwest.

View Article: PubMed Central - PubMed

Affiliation: Climate and Health Program, Division of Environmental Hazards and Health Effects, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, 30341, GA, USA. ssaha@cdc.gov.

ABSTRACT

Background: Predictions of intense heat waves across the United States will lead to localized health impacts, most of which are preventable. There is a need to better understand the spatial variation in the morbidity impacts associated with extreme heat across the country to prevent such adverse health outcomes.

Methods: Hyperthermia-related emergency department (ED) visits were obtained from the Truven Health MarketScan(®) Research dataset for 2000-2010. Three measures of daily ambient heat were constructed using meteorological observations from the National Climatic Data Center (maximum temperature, heat index) and the Spatial Synoptic Classification. Using a time-stratified case crossover approach, odds ratio of hyperthermia-related ED visit were estimated for the three different heat measures. Random effects meta-analysis was used to combine the odds ratios for 94 Metropolitan Statistical Areas (MSA) to examine the spatial variation by eight latitude categories and nine U.S. climate regions.

Results: Examination of lags for all three temperature measures showed that the odds ratio of ED visit was statistically significant and highest on the day of the ED visit. For heat waves lasting two or more days, additional statistically significant association was observed when heat index and synoptic classification was used as the temperature measure. These results were insensitive to the inclusion of air pollution measures. On average, the maximum temperature on the day of an ED visit was 93.4°F in 'South' and 81.9°F in the 'Northwest' climatic regions of United States. The meta-analysis showed higher odds ratios of hyperthermia ED visit in the central and the northern parts of the country compared to the south and southwest.

Conclusion: The results showed spatial variation in average temperature on days of ED visit and odds ratio for hyperthermia ED visits associated with extreme heat across United States. This suggests that heat response plans need to be customized for different regions and the potential role of hyperthermia ED visits in syndromic surveillance for extreme heat.

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Related in: MedlinePlus

Results from the random effect meta-analysis of odds ratios of hyperthermia-related ED visit associated with maximum temperature grouped by latitude categories. Any MSA with less than 50 observations were excluded. The number in the boxes on top show the number of MSAs included in the meta-analysis for each latitude category. Hyperthermia data on ED visit was obtained from MarketScan research database for 2000–2010.
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Fig2: Results from the random effect meta-analysis of odds ratios of hyperthermia-related ED visit associated with maximum temperature grouped by latitude categories. Any MSA with less than 50 observations were excluded. The number in the boxes on top show the number of MSAs included in the meta-analysis for each latitude category. Hyperthermia data on ED visit was obtained from MarketScan research database for 2000–2010.

Mentions: For all three temperature metrics, temperature profiles on the day of the ED visit varied across regions. For example, maximum temperature values on the day of an ED visit were higher in the southern climatic regions compared to the northern regions on average, with a range of 93.4°F in ‘South’ and 81.9°F in the ‘Northwest’ (Table 3). Temperature profiles on days of the ED visit were hotter compared to the ‘control’ days across all climate regions. For example, among the MSAs in the ‘Central’ region, the maximum temperature on the day of an ED visit was 4.9°F higher on average compared to the ‘control’ days. However, this pattern was not uniform across regions, as case days in the north were much hotter compared to the south on average. This spatial variation in temperature profiles on days of ED visit led to the examination of the geographic variation in the odds ratio of hyperthermia-related ED visits. The odds ratio for hyperthermia-related ED visit was estimated for 94 MSAs individually which had at least 50 cases of ED visits each in the dataset (Additional file 1: Table S3). Then random-effects meta-analysis was used to derive estimates for each of the U.S. climatic regions and latitude zones. Test of heterogeneity [34] showed that the odds ratios derived for the different geographic groups of the MSAs were significantly different from each other (I2 statistic = 31.1, P < 0.003). The odds ratios for each climatic region were statistically significant, and varied from 1.07 [95% confidence interval: 1.01, 1.15] in the Southwest region to 1.18 [95% confidence interval: 1.15, 1.21] in the East North Central region (Figure 1). The odds ratios for each latitude category were statistically significant, and varied from 1.11 [95% confidence interval: 1.07, 1.14] in the southernmost MSAs to 1.17 [95% confidence interval: 1.14, 1.19] in the northernmost MSAs (Figure 2). Odds ratio of ED visits were relatively higher in the northern MSAs (within 36°N and 42°N latitudes), compared to those below 36°N. Summary results from the meta-analyses using heat index and SSC produced very similar spatial patterns which are presented in the (Additional file 1: Table S4).Table 3


Spatial variation in hyperthermia emergency department visits among those with employer-based insurance in the United States - a case-crossover analysis.

Saha S, Brock JW, Vaidyanathan A, Easterling DR, Luber G - Environ Health (2015)

Results from the random effect meta-analysis of odds ratios of hyperthermia-related ED visit associated with maximum temperature grouped by latitude categories. Any MSA with less than 50 observations were excluded. The number in the boxes on top show the number of MSAs included in the meta-analysis for each latitude category. Hyperthermia data on ED visit was obtained from MarketScan research database for 2000–2010.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4352547&req=5

Fig2: Results from the random effect meta-analysis of odds ratios of hyperthermia-related ED visit associated with maximum temperature grouped by latitude categories. Any MSA with less than 50 observations were excluded. The number in the boxes on top show the number of MSAs included in the meta-analysis for each latitude category. Hyperthermia data on ED visit was obtained from MarketScan research database for 2000–2010.
Mentions: For all three temperature metrics, temperature profiles on the day of the ED visit varied across regions. For example, maximum temperature values on the day of an ED visit were higher in the southern climatic regions compared to the northern regions on average, with a range of 93.4°F in ‘South’ and 81.9°F in the ‘Northwest’ (Table 3). Temperature profiles on days of the ED visit were hotter compared to the ‘control’ days across all climate regions. For example, among the MSAs in the ‘Central’ region, the maximum temperature on the day of an ED visit was 4.9°F higher on average compared to the ‘control’ days. However, this pattern was not uniform across regions, as case days in the north were much hotter compared to the south on average. This spatial variation in temperature profiles on days of ED visit led to the examination of the geographic variation in the odds ratio of hyperthermia-related ED visits. The odds ratio for hyperthermia-related ED visit was estimated for 94 MSAs individually which had at least 50 cases of ED visits each in the dataset (Additional file 1: Table S3). Then random-effects meta-analysis was used to derive estimates for each of the U.S. climatic regions and latitude zones. Test of heterogeneity [34] showed that the odds ratios derived for the different geographic groups of the MSAs were significantly different from each other (I2 statistic = 31.1, P < 0.003). The odds ratios for each climatic region were statistically significant, and varied from 1.07 [95% confidence interval: 1.01, 1.15] in the Southwest region to 1.18 [95% confidence interval: 1.15, 1.21] in the East North Central region (Figure 1). The odds ratios for each latitude category were statistically significant, and varied from 1.11 [95% confidence interval: 1.07, 1.14] in the southernmost MSAs to 1.17 [95% confidence interval: 1.14, 1.19] in the northernmost MSAs (Figure 2). Odds ratio of ED visits were relatively higher in the northern MSAs (within 36°N and 42°N latitudes), compared to those below 36°N. Summary results from the meta-analyses using heat index and SSC produced very similar spatial patterns which are presented in the (Additional file 1: Table S4).Table 3

Bottom Line: Random effects meta-analysis was used to combine the odds ratios for 94 Metropolitan Statistical Areas (MSA) to examine the spatial variation by eight latitude categories and nine U.S. climate regions.These results were insensitive to the inclusion of air pollution measures.The meta-analysis showed higher odds ratios of hyperthermia ED visit in the central and the northern parts of the country compared to the south and southwest.

View Article: PubMed Central - PubMed

Affiliation: Climate and Health Program, Division of Environmental Hazards and Health Effects, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, 30341, GA, USA. ssaha@cdc.gov.

ABSTRACT

Background: Predictions of intense heat waves across the United States will lead to localized health impacts, most of which are preventable. There is a need to better understand the spatial variation in the morbidity impacts associated with extreme heat across the country to prevent such adverse health outcomes.

Methods: Hyperthermia-related emergency department (ED) visits were obtained from the Truven Health MarketScan(®) Research dataset for 2000-2010. Three measures of daily ambient heat were constructed using meteorological observations from the National Climatic Data Center (maximum temperature, heat index) and the Spatial Synoptic Classification. Using a time-stratified case crossover approach, odds ratio of hyperthermia-related ED visit were estimated for the three different heat measures. Random effects meta-analysis was used to combine the odds ratios for 94 Metropolitan Statistical Areas (MSA) to examine the spatial variation by eight latitude categories and nine U.S. climate regions.

Results: Examination of lags for all three temperature measures showed that the odds ratio of ED visit was statistically significant and highest on the day of the ED visit. For heat waves lasting two or more days, additional statistically significant association was observed when heat index and synoptic classification was used as the temperature measure. These results were insensitive to the inclusion of air pollution measures. On average, the maximum temperature on the day of an ED visit was 93.4°F in 'South' and 81.9°F in the 'Northwest' climatic regions of United States. The meta-analysis showed higher odds ratios of hyperthermia ED visit in the central and the northern parts of the country compared to the south and southwest.

Conclusion: The results showed spatial variation in average temperature on days of ED visit and odds ratio for hyperthermia ED visits associated with extreme heat across United States. This suggests that heat response plans need to be customized for different regions and the potential role of hyperthermia ED visits in syndromic surveillance for extreme heat.

Show MeSH
Related in: MedlinePlus